Cisco Catalyst 3550 Series Switches

Release Notes for the Catalyst 3550 Multilayer Switch Cisco IOS Release 12.1(11)EA1

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Release Notes for the Catalyst 3550 Multilayer Switch Cisco IOS Release 12.1(11)EA1

Table Of Contents

Release Notes for the
Catalyst 3550 Multilayer Switch
Cisco IOS Release 12.1(11)EA1


System Requirements

Hardware Supported

Software Compatibility

Recommended Platform Configuration for Web-Based Management

Operating System and Browser Support

Installing the Required Plug-In

Creating Clusters with Different Releases of IOS Software

Downloading Software

Determining the Software Version and Feature Set

Which Files to Use

Upgrading a Switch by Using CMS

Upgrading a Switch by Using the CLI

Upgrading with a Nondefault System MTU Setting

Recovering from Software Failure

Installation Notes

Setting Up the Catalyst 3550 Initial Configuration

Accessing CMS

New Features

New Hardware Features

New Software Features

Limitations and Restrictions

IOS Limitations and Restrictions

Cluster Limitations and Restrictions

CMS Limitations and Restrictions

Important Notes

IOS Notes

Cluster Notes

CMS Notes

Read-Only Mode in CMS

Open Caveats

Open IOS Caveats

Open Cluster Caveats

Open CMS Caveats

Resolved Caveats

Resolved IOS Caveats

Resolved CMS Caveats

Documentation Updates


Related Documentation

Obtaining Documentation

World Wide Web

Documentation CD-ROM

Ordering Documentation

Documentation Feedback

Obtaining Technical Assistance

Technical Assistance Center

Contacting TAC by Using the Cisco TAC Website

Contacting TAC by Telephone

Release Notes for the
Catalyst 3550 Multilayer Switch
Cisco IOS Release 12.1(11)EA1

August 2002

The Cisco IOS Release 12.1(11)EA1 runs on all Catalyst 3550 multilayer switches.

These release notes include important information about this IOS release and any limitations, restrictions, and caveats that apply to it. Verify that these are the correct release notes for your switch:

If you are installing a new switch, refer to the IOS release label on the rear panel of your switch.

If your switch is on, use the show version privileged EXEC command. See the "Determining the Software Version and Feature Set" section.

If you are upgrading to a new release, refer to the software upgrade filename for the IOS version.

For the complete list of Catalyst 3550 switch documentation, see the "Related Documentation" section.

This IOS release is part of a special release of Cisco IOS software that is not released on the same 8-week maintenance cycle that is used for other platforms. As maintenance releases and future IOS releases become available, they will be posted to (previously Cisco Connection Online [CCO]) in the Cisco IOS software area.


This information is in the release notes:

"System Requirements" section

"Downloading Software" section

"Installation Notes" section

"New Features" section

"Limitations and Restrictions" section

"Important Notes" section

"Open Caveats" section

"Resolved Caveats" section

"Documentation Updates" section

"Related Documentation" section

"Obtaining Documentation" section

"Obtaining Technical Assistance" section

System Requirements

These are the system requirements for this IOS release:

"Hardware Supported" section

"Software Compatibility" section

Hardware Supported

Table 1 lists the hardware supported by this IOS release.

Table 1 Supported Hardware 


Catalyst 3550-12T

10 Gigabit Ethernet 10/100/1000BASE-T ports and 2 GBIC1 -based Gigabit Ethernet slots

Catalyst 3550-12G

10 GBIC-based Gigabit Ethernet slots and 2 Gigabit Ethernet 10/100/1000BASE-T ports

Catalyst 3550-24

24 autosensing 10/100 Ethernet ports and 2 GBIC-based Gigabit Ethernet slots

Catalyst 3550-48

48 autosensing 10/100 Ethernet ports and 2 GBIC-based Gigabit Ethernet slots

Catalyst 3550-24-FX

24 100BASE-FX ports and 2 GBIC-based Gigabit Ethernet slots

Catalyst 3550-24-DC

24 autosensing 10/100 Ethernet ports, 2 GBIC-based Gigabit Ethernet slots, and an on-board direct-current (DC) power converter

GBIC modules





GigaStack GBIC

Course Wave Division Multiplexer (CWDM) fiber-optic GBIC

Redundant power system

Cisco RPS 300 Redundant Power System

1 GBIC = Gigabit Interface Converter

Software Compatibility

These are the software compatibility requirements for this IOS release:

"Recommended Platform Configuration for Web-Based Management" section

"Operating System and Browser Support" section

"Installing the Required Plug-In" section

"Creating Clusters with Different Releases of IOS Software" section

Recommended Platform Configuration for Web-Based Management

Table 2 lists the recommended platforms for Web-based management.

Table 2 Recommended Platform Configuration for Web-Based Management

Processor Speed
Number of Colors
Font Size

Windows NT 4.01

Pentium 300 MHz

128 MB


1024 x 768


Solaris 2.5.1 or higher


128 MB

Most colors for applications

Small (3)

1 Service Pack 3 or higher is required.

The minimum PC requirement is a Pentium processor running at 233 MHz with 64 MB of DRAM. The minimum UNIX workstation requirement is a Sun Ultra 1 running at 143 MHz with 64 MB of DRAM.

For information about supported operating systems, see the next section.

Operating System and Browser Support

You can access the web-based interfaces by using the operating systems and browsers listed in Table 3. The switch checks the browser version when starting a session to ensure that the browser is supported. If the browser is not supported, the switch displays an error message, and the session does not start.

Table 3 Supported Operating Systems and Browsers

Operating System
Minimum Service Pack or Patch
Netscape Communicator 1
Microsoft Internet Explorer 2

Windows 95

Service Pack 1

4.75 or 6.2

5.5 or 6.0

Windows 98

Second Edition

4.75 or 6.2

5.5 or 6.0

Windows NT 4.0

Service Pack 3 or later

4.75 or 6.2

5.5 or 6.0

Windows 2000


4.75 or 6.2

5.5 or 6.0

Windows XP


4.75 or 6.2

5.5 or 6.0

Solaris 2.5.1 or later

Sun-recommended patch cluster for the OS and Motif library patch 103461-24

4.75 or 6.2

Not supported

1 Netscape Communicator version 6.0 is not supported.

2 Service Pack 1 or higher is required for Internet Explorer 5.5.

Note If your browser is Internet Explorer and you receive an error message stating that the page might not display correctly because your security settings prohibit running activeX controls, this might mean that your security settings are set too high. To lower security settings, go to Tools > Internet Options, and select the Security tab. Select the indicated Zone, and move the Security Level for this Zone slider from High to Medium (the default).

Note In Cluster Management displays, Internet Explorer versions 4.01 and 5.0 might not display edge devices that are not connected to the command switch. Other functionality is similar to that of Netscape Communicator.

Installing the Required Plug-In

A Java plug-in is required for the browser to access and run the Java-based Cluster Management Suite (CMS). Download and install the plug-in before you start CMS. Each platform, Windows and Solaris, supports three plug-in versions. For information on the supported plug-ins, see the "Windows XP, Windows 2000, Windows 95, Windows 98, and Windows NT 4.0 Plug-Ins" section and the "Solaris Platforms" section.

You can download the recommended plug-ins from this URL:

Note Uninstall older versions of the Java plug-ins before installing the Java plug-in.

If the Java applet does not initialize after you have installed the plug-in, open the Java Plug-in Control Panel (Start > Programs > Java Plug-in Control Panel), and verify these settings:

In the Proxies tab, verify that Use browser settings is checked and that no proxies are enabled.

Note If you are running an Internet virus checker on Windows 2000 and the plug-in takes a long time to load, you can speed up CMS operation by disabling the virus checker filter option or download option or both.

On McAfee VirusScan, from the Start menu, to disable the VirusScan Internet Filter option, the Download Scan option, or both, select Start > Programs > Network Associates > Virus Scan Console > Configure.


From the taskbar, right-click the Virus Shield icon and in the Quick Enable menu, disable the options by deselecting Internet Filter or Download Scan.

Windows XP, Windows 2000, Windows 95, Windows 98, and Windows NT 4.0 Plug-Ins

These Java plug-ins are supported in Windows environments:

Java plug-in 1.4

Java plug-in 1.3.1

Java plug-in 1.3.0

You can download these plug-ins from this URL:

Note If you start CMS without having installed the required Java plug-in, the browser automatically detects this. If you are using a supported Internet Explorer browser, it automatically downloads and installs the Java plug-in 1.4 (default). If you are using a supported Netscape browser, the browser displays a page that contains the Java plug-in and installation instructions. If you are using Windows 2000, Netscape Communicator might not detect the missing Java plug-in.

Solaris Platforms

These Java plug-ins are supported on the Solaris platform:

Java plug-in 1.4

Java plug-in 1.3.1

Java plug-in 1.3.0

You can download these plug-ins and instructions from this URL:

To install the Java plug-in, follow the instructions in the README_FIRST.txt file.

Creating Clusters with Different Releases of IOS Software

When a cluster consists of a mixture of other Catalyst switches, we strongly recommend using only the Catalyst 3550 switches as the command and standby command switches. When the command switch is a Catalyst 3550 switch, all standby command switches must also be Catalyst 3550 switches. The Catalyst 3550 switch that has the latest software should be the command switch. If the command switch is a Catalyst 3550 Gigabit Ethernet switch and the standby command switch is a Catalyst 3550 Fast Ethernet switch, command switch port speeds are reduced if the standby command switch takes over.

If your cluster has Catalyst 2950, Catalyst 2900 XL, and Catalyst 3500 XL switches, the Catalyst 2950 switch (with the latest software release) should be the command switch. The Catalyst 2950 switch that has the latest software should be the command switch.

If your switch cluster has Catalyst 1900, Catalyst 2820, Catalyst 2900 XL, and Catalyst 3500 XL switches, either the Catalyst 2900 XL or Catalyst 3500 XL (whichever has the latest software release) should be the command switch.

Table 4 lists the cluster capabilities and software versions for the switches.

Table 4 Switch Software and Cluster Capability

IOS Release
Cluster Capability

Catalyst 3550

Release 12.1(4)EA1 or later

Member or command switch

Catalyst 3500 XL

Release 12.0(5.1)XU or later

Member or command switch

Catalyst 2950

Release 12.0(5.2)WC(1) or later

Member or command switch

Catalyst 2900 XL (8-MB switches)

Release 12.0(5.1)XU or later

Member or command switch

Catalyst 2900 XL (4-MB switches)

Release 11.2(8.5)SA6 (recommended)

Member switch only1

Catalyst 1900 and 2820

Release 9.00(-A or -EN) or later

Member switch only

1 Catalyst 2900 XL (4-MB) switches appear in the front-panel and topology views of CMS. However, CMS does not support configuration or monitoring of these switches.

Some versions of the Catalyst 2900 XL software do not support clustering and if you have a cluster with switches that are running different versions of IOS software, software features added on the latest release might not be reflected on switches running the older versions. For example, if you start Visual Switch Manager (VSM) on a Catalyst 2900 XL switch running Release 11.2(8)SA6, the windows and functionality can be different from a switch running Release 12.0(5)WC(1) or later.

Note The CMS is not forward-compatible, which means that if a member switch is running a software version that is newer than the release running on the command switch, the new features are not available on the member switch. If the member switch is a new device supported by a software release that is later than the software release on the command switch, the command switch cannot recognize the member switch and it is displayed as an unknown device in the Front Panel view. You cannot configure any parameters or generate a report through CMS for that member; instead, you must launch the Device Manager application to perform configuration and obtain reports for that member.

Downloading Software

These are the procedures for downloading software:

"Determining the Software Version and Feature Set" section

"Which Files to Use" section

"Upgrading a Switch by Using CMS" section

"Upgrading a Switch by Using the CLI" section

Note Before downloading software, read this section for important information.

Caution The crypto image includes a bootloader upgrade. Do not power cycle the switch while you are copying this image to the switch. If a power failure occurs when you are copying this image to the switch, call Cisco Systems immediately.

Determining the Software Version and Feature Set

The IOS image is stored as a .bin file in a directory that is named with the IOS release. A subdirectory contains the HTML files needed for web management. The image is stored on the system board Flash device (flash:).

You can use the show version privileged EXEC command to see the software version that is running on your switch. The second line displays C3550-I5Q3L2 for the enhanced multilayer software image (EMI) or C3550-I9Q3L2 for the standard multilayer software image (SMI).

Note Although the show version output always shows the software image running on the switch (Layer 2 or Layer 2/3), the model name shown at the end of this display is the factory configuration (SMI or EMI) and does not change if you upgrade the software image.

You can also use the dir filesystem: privileged EXEC command to see the directory names of other software images that you might have stored in Flash memory.

Which Files to Use

The upgrade procedures in these release notes describe how to perform the upgrade by using a combined .tar file. This file contains both the IOS image file and the HTML files (needed for the CMS). You must use the combined .tar file to upgrade the switch through the CMS.

The .tar file is an archive file from which you can extract files by using the tar command. You also use the .tar file to upgrade the system by using the archive download-sw privileged EXEC command.

Table 5 lists the software file names for this IOS release.

Table 5 Cisco IOS Software Files for Catalyst 3550 Switches




IOS SMI image file and CMS files.
This image has Layer 2+ and basic Layer 3 routing features.


IOS EMI image file and CMS files.
This image has both Layer 2+ and full Layer 3 features.


IOS SMI crypto image file and CMS files.
This image has the secure shell (SSH) and Layer 2+ features.


IOS EMI crypto image file and CMS files.
This image has the SSH, Layer 2, and Layer 3 features.

The Catalyst 3550 switch is supported by either the SMI, which provides Layer 2+ features and basic Layer 3 routing, or the EMI, which provides Layer 2+ features, full Layer 3 routing, and advanced services. All Catalyst 3550 Gigabit Ethernet switches are shipped with the EMI installed. Catalyst 3550 Fast Ethernet switches are shipped with either the SMI or the EMI installed. After initial deployment, you can order the Enhanced Multilayer Software Image Upgrade kit to upgrade the Catalyst 3550 Fast Ethernet switches from the SMI to the EMI.

Upgrading a Switch by Using CMS

You can upgrade switch software by using CMS. From the menu bar, select Administration > Software Upgrade. For detailed instructions, click Help.

Caution If you are copying the crypto image to the switch, the bootloader can take up to 30  seconds to upgrade. Do not power cycle the switch while you are copying the image to the switch. If a power failure occurs when you are copying the image, call Cisco Systems immediately.

Upgrading a Switch by Using the CLI

This procedure is for copying the combined .tar file to the Catalyst 3550 switch. You copy the file to the switch from a TFTP server and extract the files. You can download an image file and replace or keep the current image.

Caution If you are copying the crypto image to the switch, the bootloader can take up to 30  seconds to upgrade. Do not power cycle the switch while you are copying the image to the switch. If a power failure occurs when you are copying the image, call Cisco Systems immediately.

To download software, and if necessary, the TFTP server application, follow these steps:

Step 1 Use Table 5 to identify the file that you want to download.

Step 2 Download the software image file.

If you have a SmartNet support contract, go to this URL and log in to download the appropriate files:

If you do not have a SmartNet contract, go to this URL and follow the instructions to register on and download the appropriate files:

To download the SMI and EMI files, select Download Cisco Catalyst 3550 software.

To obtain authorization and to download the crypto software files, select Download Cisco Catalyst 3550 3DES Cryptographic Software under export licensing controls.

Step 3 Download the Cisco TFTP server from the URL link from Step 2, if necessary. The information on this page describes how to download and configure the TFTP server.

Step 4 Copy the image to the appropriate TFTP directory on the workstation, and make sure the TFTP server is properly configured.

For more information, refer to Appendix B in the Catalyst 3550 Multilayer Switch Software Configuration Guide.

Step 5 Log in to the switch through the console port or a Telnet session.

Step 6 Check your VLAN 1 configuration by using the show interfaces vlan 1 privileged EXEC command, and verify that VLAN 1 is part of the same network as the TFTP server. (Check the Internet address is line near the top of the display.)

Step 7 Download the image file from the TFTP server to the switch. If you are installing the same version of software that is currently on the switch, overwrite the current image by using this privileged EXEC command:

archive download-sw /overwrite /reload tftp:[[//location]/directory]/image-name.tar

The /overwrite option overwrites the software image in Flash memory with the downloaded one.

The /reload option reloads the system after downloading the image unless the configuration has been changed and not been saved.

For //location, specify the IP address of the TFTP server.

For /directory/image-name.tar, specify the directory (optional) and the image to download. Directory and image names are case sensitive.

This example shows how to download an image from a TFTP server at and to overwrite the image on the switch:

Switch# archive download-sw /overwrite tftp://

You can also download the image file from the TFTP server to the switch and keep the current image by replacing the /overwrite option with the /leave-old-sw option.

Upgrading with a Nondefault System MTU Setting

If the switch was running Release 12.1(8)EA1c or earlier and you had used the system mtu global configuration command to configure a nondefault system maximum transmission unit (MTU) size on your switch, follow these steps to upgrade your switch to 12.1(11)EA1 or later:

Step 1 Upgrade the IOS software to 12.1(11)EA1 or later.

Step 2 If a system MTU size of greater than 2000 is configured on the Catalyst 3550-12T or Catalyst 3550-12G, use the system mtu global configuration command to set it to the maximum supported MTU size.

Note The maximum allowable system MTU for Catalyst 3550 Gigabit Ethernet switches is 2000 bytes; the maximum system MTU for Fast Ethernet switches is 1546 bytes.

Step 3 Save the running configuration by entering the copy running-config startup-config privileged EXEC command.

Step 4 Reload the switch by using the new IOS software.

Step 5 When the switch comes back up with 12.1(11)EA1 or later, reload the switch a second time by using the reload privileged EXEC command so that the system mtu command takes effect.

Recovering from Software Failure

If the software fails, you can reload the software. For detailed recovery procedures, refer to the "Troubleshooting" chapter in the Catalyst 3550 Multilayer Switch Software Configuration Guide.

Installation Notes

You can assign IP information to your switch by using the setup program, the Dynamic Host Configuration Protocol (DHCP)-based autoconfiguration (refer to the Catalyst 3550 Multilayer Switch Software Configuration Guide), or by manually assigning an IP address (refer to the Catalyst 3550 Multilayer Switch Software Configuration Guide).

These are the installation procedures:

"Setting Up the Catalyst 3550 Initial Configuration" section

"Accessing CMS" section

Setting Up the Catalyst 3550 Initial Configuration

The first time that you access the switch, it runs a setup program that prompts you for an IP address and other configuration information necessary for the switch to communicate with the local routers and the Internet. This information is also required if you plan to use the CMS to configure and manage the switch.

Note If the switch will be a cluster member managed through the IP address of the command switch, it is not necessary to assign IP information or a password. If you are configuring the switch as a standalone switch or as a command switch, you must assign IP information.

Follow these steps to create an initial configuration for the switch:

Step 1 Enter Yes at the first two prompts.

Would you like to enter the initial configuration dialog? [yes/no]: yes

At any point you may enter a question mark '?' for help.
Use ctrl-c to abort configuration dialog at any prompt.
Default settings are in square brackets '[]'.

Basic management setup configures only enough connectivity
for management of the system, extended setup will ask you
to configure each interface on the system.

Would you like to enter basic management setup? [yes/no]: yes

Step 2 Enter a host name for the switch, and press Return.

On a command switch, the host name is limited to 28 characters; on a member switch to 31 characters. Do not use -n, where n is a number, as the last character in a host name for any switch.

Enter host name [Switch]: host_name

Step 3 Enter a secret password, and press Return.

The password can be from 1 to 25 alphanumeric characters, can start with a number, is case sensitive, allows spaces, but ignores leading spaces.

Enter enable secret: secret_password

Step 4 Enter an enable password, and press Return.

Enter enable password: enable_password

Step 5 Enter a virtual terminal (Telnet) password, and press Return.

The password can be from 1 to 25 alphanumeric characters, is case sensitive, allows spaces, but ignores leading spaces.

Enter virtual terminal password: terminal-password

Step 6 (Optional) Configure Simple Network Management Protocol (SNMP) by responding to the prompts.

Step 7 Enter the interface name (physical interface or VLAN name) of the interface that connects to the management network, and press Return. For this release, always use vlan 1 as that interface.

Enter interface name used to connect to the
management network from the above interface summary: vlan 1

Step 8 Configure the interface by entering the switch IP address and subnet mask and pressing Return:

Configuring interface vlan 1:
Configure IP on this interface? [yes]: yes 
IP address for this interface:
Subnet mask for this interface []:

Step 9 Enter Y to configure the switch as the cluster command switch. Enter N to configure it as a member switch or as a standalone switch.

If you enter N, the switch appears as a candidate switch in the CMS. In this case, the message in Step 10 is not displayed.

Would you like to enable as a cluster command switch? [yes/no]: yes

Step 10 Assign a name to the cluster, and press Return.

Enter cluster name: cluster_name

The cluster name can be 1 to 31 alphanumeric characters, dashes, or underscores.

The initial configuration appears:

The following configuration command script was created:

hostname host-name
enable secret 5 $1$LiBw$0Xc1wyT.PXPkuhFwqyhVi0
enable password enable-password
line vty 0 15
password terminal-password
snmp-server community public
no ip routing
interface vlan 1
no shutdown
ip address

interface GigabitEthernet0/1
no ip address
interface GigabitEthernet0/2
no ip address
...<output abbreviated>
interface GigabitEthernet0/12
no ip address

cluster enable cluster-name

Step 11 These choices are displayed:

[0] Go to the IOS command prompt without saving this config.

[1] Return back to the setup without saving this config.

[2] Save this configuration to nvram and exit.

Enter your selection [2]:2

Make your selection, and press Return.

After you complete the setup program, the switch can run the created default configuration. If you want to change this configuration or want to perform other management tasks, use one of these tools:

Command-line interface (CLI)

Cluster Management Suite (CMS) from your browser

Accessing CMS

Before the browser can use the CMS, a Java plug-in is required, as described in the "Installing the Required Plug-In" section. After you have assigned an IP address to the switch and installed the plug-in, you can access the switch from your browser and use the CMS to configure other switches.

Note If you have downloaded a new version of the CMS, you must clear your browser cache before launching the new CMS version.

To use the web-based tools, see the "Software Compatibility" section to set up the appropriate browser options.

To display the CMS access page, follow these steps:

Step 1 Enter the switch IP address in the browser Location field (Netscape Communicator) or Address field (Internet Explorer), and press Return.

Step 2 Enter your username and password when prompted.

Note The browser always prompts for username and password. If no username is configured on your switch, you only need to enter the enable password in the appropriate field.

The Cisco Systems Access page appears. For more information on setting passwords and privilege levels, refer to the Catalyst 3550 Multilayer Switch Software Configuration Guide.

Step 3 Click Web Console to launch the CMS applet.

When you access CMS from a standalone or a cluster-member switch, Device Manager appears.

New Features

These are the new supported hardware and the new software features provided in IOS Release 12.1(11)EA1:

"New Hardware Features" section

"New Software Features" section

New Hardware Features

There is no new hardware is offered with this release. For a list of supported hardware, see the "Hardware Supported" section.

New Software Features

Cisco IOS Release 12.1(11)EA1 contains these new features or enhancements:

Simple Network Management Protocol Version 3 (SNMPv3) to increase network security by authenticating and encrypting packets

Basic routing functionality, including static unicast routing and the Routing Information Protocol (RIP), in the SMI

Trusted boundary to detect the presence of a Cisco IP phone, to trust the Class of Service (CoS) value received, and to ensure port security

Per-port per-VLAN ingress quality of service (QoS) policing for classification of traffic on a physical interface or on a per-port per-VLAN basis

Remote SPAN (RSPAN) for traffic monitoring on any port or VLAN

Support for the Unidirectional Link Detection (UDLD) aggressive mode

Support for dynamic-secure addresses that you can save in the configuration file

CMS support for these features:

Switch Configuration Save and Restore—save a switch configuration to a TFTP server and later restore the configuration file to one or more switches

CMS preferences—save the CMS preferences to your PC instead of saving the preferences to Flash memory on the switch

Menu bar options—access the new alarm notification, event notification, restore configuration, and user and password features

CISCO-ENTITY-MIB support for the Catalyst 3550 in compliance with RFC-2737

The CISCO-PORT-QOS-MIB to enable SNMP queries of QoS statistics to use for billing purposes

Encrypted Secure Shell (SSH) connections for multiple CLI-based sessions over the network (requires the crypto image file; see Table 5)

Routing support for the Border Gateway Protocol (BGP-4) (EMI only)

Support for multiple virtual private networks (VPNs) with overlapping IP addresses in service provider networks by using multiple VPN routing/forwarding (multi-VRF) instances in customer edge (CE) devices with the multi-VRF CE feature (EMI only)

Web Cache Communication Protocol (WCCP) to redirect traffic to local cache engines, enable content requests to be fulfilled locally, and to localize web-traffic patterns in the network (EMI only)

The CISCO-L2L3-INTERFACE-MIB to enable the Cisco Campus Manager software to properly represent the switch on its topology map and to identify ports as routed or switched (EMI only)

Limitations and Restrictions

You should review this section before you begin working with the switches. These are known limitations that will not be fixed, and there is not always a workaround. Some features might not work as documented, and some features could be affected by recent changes to the switch hardware or software.

These are the limitations and restrictions:

"IOS Limitations and Restrictions" section

"Cluster Limitations and Restrictions" section

"CMS Limitations and Restrictions" section

IOS Limitations and Restrictions

These limitations apply to IOS configuration:

Storm control or traffic suppression (configured by using the storm-control {broadcast | multicast | unicast} level level [.level] interface configuration command) is supported only on physical interfaces; it is not supported on EtherChannel port channels even though you can enter these commands through the CLI.

The Cisco RPS 300 Redundant Power System supports the Catalyst 3550 multilayer switch and provides redundancy for up to six connected devices until one of these devices requires backup power. If a connected device has a power failure, the RPS immediately begins supplying power to that device and sends status information to other connected devices that it is no longer available as a backup power source. As described in the device documentation, when the RPS LED is amber, the RPS is connected but down. However, this might merely mean that the RPS is in standby mode. Press the Standby/Active button on the RPS to put it into active mode. You can view RPS status through the CLI by using the show rps privileged EXEC command. For more information, refer to the RPS 300 Hardware Installation Guide.

You can connect the switch to a PC by using the switch console port and the supplied rollover cable and the DB-9 adapter. You need to provide a RJ-45-to-DB-25 female DTE adapter if you want to connect the switch console port to a terminal. You can order a kit (part number ACS-DSBUASYN=) with this RJ-45-to-DB-25 female DTE adapter from Cisco.

Modifying a multicast boundary access list does not prevent packets from being forwarded by any multicast routes that were in existence before the access list was modified if the packets arriving on the input interface do not violate the boundary. However, no new multicast routes that violate the updated version of the multicast boundary access list are learned, and any multicast routes that are in violation of the updated access list are not relearned if they age out.

After updating a multicast boundary, the workaround is to use the clear ip mroute privileged EXEC command to delete any existing multicast routes that violate the updated boundary. (CSCdr79083)

When an IP packet with a cyclic redundancy check (CRC) error is received, the per-packet per-DSCP counter (for DSCP 0) is incremented. Normal networks should not have packets with CRC errors. (CSCdr85898)

The mac-address interface configuration command does not properly assign a MAC address to an interface. This command is not supported on Catalyst 3550 switches. (CSCds11328)

If you configure the DHCP server to allocate addresses from a pool to the switch, two devices on the network might have the same IP address. Pooled addresses are temporarily allocated to a device and are returned to the pool when not in use. If you save the configuration file after the switch receives such an address, the pooled address is saved, and the switch does not attempt to access the DHCP server after a reboot to receive a new IP address. As a result, two devices might have the same IP address.

The workaround is to make sure that you configure the DHCP server with reserved leases that are bound to each switch by the switch hardware address. (CSCds55220)

The show ip mroute count privileged EXEC command might display incorrect packet counts. In certain transient states (for example, when a multicast stream is forwarded only to the CPU during the route-learning process and the CPU is programming this route into the hardware), a multicast stream packet count might be counted twice. Do not trust the counter during this transient state. (CSCds61396)

When changing the link speed of a Gigabit Ethernet port from 1000 Mbps to 100 Mbps, there is a slight chance that the port will stop transmitting packets. If this occurs, shut down the port, and re-enable it by using the shutdown and no shutdown interface configuration commands. (CSCds84279)

In IP multicast routing and fallback bridging, certain hardware features are used to replicate packets for the different VLANs of an outgoing trunk port. If the incoming speed is line rate, the outgoing interface cannot duplicate that speed (because of the replication of the packets). As a result, certain replicated packets are dropped. (CSCdt06418)

When you use the no interface port-channel global configuration command to remove an EtherChannel group, the ports in the port group change to the administratively down state.

When you remove an EtherChannel group, enter the no shutdown interface configuration command on the interfaces that belonged to the port group to bring them back on line. (CSCdt10825)

In the output displayed after a show interface interface-id privileged EXEC command, the output buffer failures field shows the number of packets lost before replication, whereas the packets output field shows the successful transmitted packets after replication. To determine actual discarded frames, multiply the output buffer failures by the number of VLANs on which the multicast data is replicated. (CSCdt26928)

Internet Group Management Protocol (IGMP) packets classified by QoS to map the Differentiated Service Code Point (DSCP) value and the class of service (CoS) value in a QoS policy map might only modify the DSCP property and leave the CoS value at zero. (CSCdt27705)

If you assign both tail-drop threshold percentages to 100 percent by using the wrr-queue threshold interface configuration command and display QoS information for this interface by using the show mls qos interface statistics privileged command, the drop-count statistics are always zero even if the thresholds were exceeded. To display the total number of discarded packets, use the show controllers ethernet-controllers interface-id privileged EXEC command. In the display, the number of discarded frames includes the frames that were dropped when the tail-drop thresholds were exceeded. (CSCdt29703)

Open Shortest Path First (OSPF) path costs and Interior Gateway Routing Protocol (IGRP) metrics are incorrect for switch virtual interface (SVI) ports. You can manually configure the bandwidth of the SVI by using the bandwidth interface configuration command. Changing the bandwidth of the interface changes the routing metric for the routes when the SVI is used as an outgoing interface. (CSCdt29806)

On the Catalyst 3550, coldStart and warmStart traps are not consistently sent. (CSCdt33779)

Remote Monitoring (RMON) collection functions on physical interfaces, but it is not supported on EtherChannels and SVIs. (CSCdt36101)

Multicast router information is displayed in the show ip igmp snooping mrouter privileged EXEC command when IGMP snooping is disabled. Multicast VLAN Registration (MVR) and IGMP snooping use the same commands to display multicast router information. In this case, MVR is enabled, and IGMP snooping is disabled. (CSCdt48002)

When a VLAN interface has been disabled and restarted multiple times by using the shutdown and no shutdown interface configuration commands, the interface might not restart following a no shutdown command. To restart the interface, re-enter a shutdown and no shutdown command sequence. (CSCdt54435)

When you configure the ip pim spt-threshold infinity interface configuration command, you want all sources for the specified group to use the shared tree and not use the source tree. However, the switch does not automatically start to use the shared tree. No connectivity problem occurs, but the switch continues to use the shortest path tree for multicast group entries already installed in the multicast routing table. You can enter the clear ip mroute * privileged EXEC command to force the change to the shared tree. (CSCdt60412)

If the number of multicast routes configured on the switch is greater than the switch can support, it might run out of available memory, which can cause it to reboot. This is a limitation in the platform-independent code.

The workaround is to not configure the switch to operate with more than the maximum number of supported multicast routes. You can use the show sdm prefer and show sdm prefer routing privileged EXEC commands to view approximate maximum configuration guidelines for the current SDM template and the routing template. (CSCdt63354)

Configuring too many multicast groups might result in an extremely low memory condition and cause the software control data structure to go out of sync, causing unpredictable forwarding behavior. The memory resources can only be recovered by issuing the clear ip mroute privileged EXEC command. To prevent this situation, do not configure more than the recommended multicast routes on the switch. (CSCdt63480)

The dec keyword is not supported in the bridge bridge-group protocol global configuration command. If two Catalyst 3550 switches are connected to each other through an interface that is configured for IP routing and fallback bridging, and the bridge group is configured with the bridge bridge-group protocol dec command, both switches act as if they were the spanning tree root. Therefore, spanning-tree loops might be undetected. (CSCdt63589)

When you configure an EtherChannel between a Catalyst 3550 and a Catalyst 1900 switch, some of Catalyst 3550 links in the EtherChannel might go down, but one link in the channel remains up, and connectivity is maintained.

The workaround is to disable the Port Aggregation Protocol (PAgP) on both devices by using the channel-group channel-group-number mode on interface configuration command. PAgP negotiation between these two devices is not reliable. (CSCdt78727)

When the switch is operating with equal-cost routes and it is required to learn more unicast routes than it can support, the CPU might run out of memory, and the switch might fail.

The workaround is to remain within the documented recommended and supported limits. (CSCdt79172)

The behavior of a software access control list (ACL) with QoS is different from a hardware ACL with QoS. On the Catalyst 3550 switch, when the QoS hardware rewrites the DSCP of a packet, the rewriting of this field happens before software running on the CPU examines the packet, and the CPU sees only the new value and not the original DSCP value.

When the security hardware ACL matches a packet on input, the match uses the original DSCP value. For output security ACLs, the security ACL hardware should match against the final, possibly changed, DSCP value as set by the QoS hardware. Under some circumstances, a match to a security ACL in hardware prevents the QoS hardware from rewriting the DSCP and causes the CPU to use the original DSCP.

If a security ACL is applied in software (because the ACL did not fit into hardware, and packets were sent to the CPU for examination), the match probably uses the new DSCP value as determined by the QoS hardware, regardless of whether the ACL is applied at the input or at the output. When packets are logged by the ACL, this problem can also affect whether or not a match is logged by the CPU even if the ACL fits into hardware and the permit or deny filtering was completed in hardware.

To avoid these issues, whenever the switch rewrites the DSCP of any packet to a value different from the original DSCP, security ACLs should not test against DSCP values in any of their access control elements (ACEs), regardless of whether the ACL is being applied to an IP access group or to a VLAN map. This restriction does not apply to ACLs used in QoS class maps.

If the switch is not configured to rewrite the DSCP value of any packet, it is safe to match against DSCP in ACLs used for IP access groups or for VLAN maps because the DSCP does not change as the packet is processed by the switch.

The DSCP field of an IP packet encompasses the two fields that were originally designated precedence and TOS (type of service). Statements relating to DSCP apply equally to either IP precedence or IP TOS. (CSCdt94355)

Disabling autonegotiation on a GBIC interface by using the speed nonegotiate interface configuration command might cause the interface to show that the physical link is up, even when it is not connected. (CSCdv29722)

If you configure a trunk port for Dynamic Trunking Protocol (DTP) nonegotiate mode and change the encapsulation type from ISL to 802.1Q by using the switchport trunk encapsulation interface configuration command, the port becomes an access port and is no longer trunking. (CSCdv46715)

On earlier versions of Catalyst 3550-24 switches, if a 10/100BASE-TX port on the switch is connected to a Catalyst 2820 or Catalyst 1900 switch through an ISL trunk at 100 Mbps, bidirectional communication cannot be established. The Catalyst 2820 or Catalyst 1900 switch identifies the Catalyst 3550-24 switch as a CDP neighbor, but the Catalyst 3550-24 switch does not recognize the Catalyst 2820 or Catalyst 1900 switch. On these switches, you should not use ISL trunks between the Catalyst 3550-24 and a Catalyst 2820 or Catalyst 1900 switch. Configure the link as an access link instead of a trunk link.

This problem has been fixed in hardware on Catalyst 3550-24 switches with motherboard assembly number 73-5700-08 or later. To determine the board level on your switch, enter the show version privileged EXEC. Motherboard information appears toward the end of the output display. (CSCdv68158)

When IGMP filtering is enabled and you use the ip igmp profile global configuration command to create an IGMP filter, reserved multicast addresses cannot be filtered. Because IGMP filtering uses only Layer 3 addresses to filter IGMP reports and due to mapping between Layer 3 multicast addresses and Ethernet multicast addresses, reserved groups (224.0.0.x) are always allowed through the switch. In addition, aliased groups can leak through the switch. For example, if a user is allowed to receive reports from group, but not from group, aliasing will cause the user to receive reports from Aliasing of reserved addresses means that all groups of the form y.0.0.x are allowed through. (CSCdv73626)

If you use the ip igmp max-groups interface configuration command to set the maximum number of IGMP groups for an interface to 0, the port still receives group reports from reserved multicast groups (224.0.0.x) and their Layer 2 aliases (y.0.0.x). (CSCdv79832)

The switch might reload when it is executing the no snmp-server host global configuration command. This is a rare condition that can happen if SNMP traps or informs are enabled and the SNMP agent attempts to send a trap to the host just as it is being removed from the configuration and if the IP address of the host (or the gateway to reach the host) has not been resolved by Address Resolution Protocol (ARP).

The workaround is to ensure that the target host or the next-hop gateway to that host is in the ARP cache (for example, by issuing a ping command) before removing it from the SNMP configuration. Alternatively, disable all SNMP traps and informs before removing any hosts from the SNMP configuration. (CSCdw44266)

When you access CISCO-STACK-MIB portTable, the mapping might be off by one from the mapping given by the switch. The objects in this table are indexed by two numbers: portModuleIndex and portIndex. The allowable values for portModuleIndex are 1 through 16. Because 0 is not an allowable value, the value 1 represents module 0.

The workaround is to use the value 1 to represent module 0. (CSCdw71848)

If a port on the Catalyst 3550 switch that is running the Multiple Spanning Tree Protocol (MSTP) is connected to another switch that belongs to a different multiple spanning tree (MST) region, the Catalyst 3550 port is not recognized as a boundary port when you start the protocol migration process by using the clear spanning-tree detected-protocols interface interface-id privileged EXEC command. This problem occurs only on the root bridge, and when the root bridge is cleared, the boundary ports are not shown because the designated ports do not receive any bridge protocol data units (BPDUs) unless a topology change occurs. This is the intended behavior.

The workaround is to configure the Catalyst 3550 switch for PVST by using the spanning-tree mode pvst global configuration command bridge, and then change it to MSTP by using the spanning-tree mode mst global configuration command. (CSCdx10808)

If you apply an ACL to an interface that has a QoS policy map attached and the ACL is configured so that the packet should be forwarded by the CPU or if the configured ACL cannot fit into the TCAM, all packets received from this interface are forwarded to the CPU. Because traffic forwarded to the CPU cannot be policed by the policer configured on the interface, this traffic is not accurately rate-limited to the configured police rate.

The workaround, when QoS rate limiting is configured on an interface, is to configure applied ACLs so that packets are not forwarded by the CPU or reduce the number of ACEs in the ACL so that it can fit into the TCAM. (CSCdx30485)

Catalyst 3550 switches do not take into account the Preamble and Inter Frame Gap (IFG) when rate limiting traffic, which could result in a slightly inaccurate policing rate on a long burst of small-sized frames, where the ratio of the Preamble and IFG to frame size is more significant. This should not be an issue in an environment where the frames are a mix of different sizes.

If the switch fails for any reason while you are exiting VLAN configuration mode (accessed by entering the vlan database privileged EXEC command), there is a slight chance that the VLAN database might get corrupted. After resetting from the switch, you might see these messages on the console:

%SW_VLAN-4-VTP_INVALID_DATABASE_DATA: VLAN manager received bad data of type device 
type: value 0 from vtp database 

$SW_VLAN-3-VTP_PROTOCOL_ERROR: VTP protocol code internal error 

The workaround is to use the delete flash:vlan.dat privileged EXEC command to delete the corrupted VLAN database. Then reload the switch by using the reload privileged EXC command. (CSCdx19540)

When a Cisco RPS 300 Redundant Power System provides power to a switch, after the switch power supply is restored the RPS 300 continues to provide power until the RPS mode button is pressed. At this point, some switches restart, depending on how quickly the switch internal power supply resumes operation. (CSCdx81023)

Inserting GigaStack Gigabit Interface Converter (GBIC) modules in the switch cause an increase in the CPU usage. (CSCdx90515)

Hot Standby Routing Protocol (HSRP) does not support configuration of overlapping addresses in different VPN routing and forwarding (VRF) tables. (CSCdy14520)

When 1000 VLANs and more than 40 trunk ports are configured, and the spanning-tree mode changes from MSTP to PVST or vice versa, this message appears on the console:

%ETHCNTR-3-RA_ALLOC_ERROR: RAM Access write pool I/O memory allocation failure

There is no workaround. However, we recommend that you reload the switch by using the reload privileged EXEC command. To avoid this problem, configure the system with fewer VLANs and fewer trunk ports, or use the switchport trunk allowed vlan interface configuration command to reduce the number of active VLANs on each trunk port. (CSCdx20106)

Cluster Limitations and Restrictions

These limitations apply to cluster configuration:

When there is a transition from the cluster active command switch to the standby command switch, Catalyst 1900, Catalyst 2820, and Catalyst 2900 4-MB switches that are cluster members might lose their cluster configuration. You must manually add these switches back to the cluster.
(CSCds32517, CSCds44529, CSCds55711, CSCds55787, CSCdt70872)

When a Catalyst 2900 XL or Catalyst 3500 XL cluster command switch is connected to a Catalyst 3550 switch, the command switch does not find any cluster candidates beyond the Catalyst 3550 switch if it is not a member of the cluster. You must add the Catalyst 3550 switch to the cluster. You can then see any cluster candidates connected to it. (CSCdt09918)

When clustering is enabled, do not configure SNMP community strings of more than 59 bytes, or clustering SNMP might not work correctly. (CSCdt39616)

If both the active command-switch and the standby command switch fail at the same time, the cluster is not automatically recreated. Even if there is a third passive command switch, it might not recreate all cluster members because it might not have all the latest cluster configuration information. You must manually recreate the cluster if both the active and standby command switches simultaneously fail. (CSCdt43501)

CMS Limitations and Restrictions

These limitations apply to CMS configuration:

Host names and Domain Name System (DNS) server names that contain commas on a cluster command switch, member switch, or candidate switch can cause CMS to behave unexpectedly. You can avoid this instability in the interface by not using commas in host names or DNS names. Do not enter commas when also entering multiple DNS names in the IP Configuration tab of the IP Management window in CMS.

ACEs that contain the host keyword precede all other ACEs in standard ACLs. You can reposition the ACEs in a standard ACL with one restriction: No ACE with the any keyword or a wildcard mask can precede an ACE with the host keyword.

CMS performance degrades if the Topology View is open for several hours on a Solaris machine. The cause might be a memory leak.

The workaround is to close the browser, reopen it, and launch CMS again. (CSCds29230)

If you are printing a Topology View or Front Panel View that contains many devices and are running Solaris 2.6 with JDK1.2.2, you might get an Out of Memory error message.

The workaround is to close the browser, re-open it, and launch CMS again. Before you perform any other task, bring up the view that you want to print, and click Print in the CMS menu.(CSCds80920)

If a PC running CMS has low memory and CMS is running continuously for two to three days, the PC runs out of memory.

The workaround is to relaunch CMS. (CSCdv88724)

When a VLAN or a range of VLANs is already configured and you specify VLAN filter for a SPAN session, the current configuration for that session is overwritten with the new entry. Although the CLI appends new entries after the existing ones, CMS recreates the whole session, overwrites the current entry, and provides only a single VLAN filter per entry.

The workaround is to use the CLI; it is the only method for specifying multiple VLANs for filtering in a SPAN session. (CSCdw93904)

Important Notes

These are the important notes related to this IOS release:

"IOS Notes" section

"Cluster Notes" section

"CMS Notes" section

"Read-Only Mode in CMS" section

IOS Notes

These notes apply to IOS configuration:

If you configure a port ACL on a physical interface on a switch that has VLAN maps or input router ACLs configured, or if you configure a VLAN map or input router ACL on a switch that has port ACLs configured, a CONFLICT message is generated but the configuration is accepted. The port ACL action has priority on that port over actions in a router ACL or VLAN map applied to the VLAN to which the port belongs.

The result is that packets received on that physical port will be permitted or denied based on the port ACL action without regard to any permit or deny statements in any router ACL or VLAN map, while packets received on other physical ports in the VLAN will still be permitted or denied based on any router ACLs or VLAN maps applied to the VLAN. If the port ACL is applied to a trunk port, it overrides any other input ACLs applied to all VLANs on the trunk port.

The default system MTU for traffic on the Catalyst 3550 switch is 1500 bytes. The 802.1Q tunneling feature increases the frame size by 4 bytes. Therefore, when you configure 802.1Q tunneling, you must configure all switches in the 802.1Q network to be able to process maximum frames by increasing the switch system MTU size to at least 1504 bytes. You configure the system MTU size by using the system mtu global configuration command.

Beginning with IOS release 12.1(8)EA1, to configure traffic suppression (previously configured by using the switchport broadcast, switchport multicast, and switchport unicast interface configuration commands), you use the storm-control {broadcast | multicast | unicast} level level [.level] interface configuration commands. For more information about these commands, refer to the Catalyst 3550 Multilayer Switch Command Reference.

When you are configuring a cascaded stack of Catalyst 3550 switches by using the GigaStack GBIC module and want to include more than one VLAN in the stack, be sure to configure all the GigaStack GBIC interfaces as trunk ports by using the switchport mode trunk interface configuration command and to use the same encapsulation method by using the switchport encapsulation {isl | dot1q} interface configuration command. For more information about these commands, refer to the Catalyst 3550 Multilayer Switch Command Reference.

If the 1000BASE-T GBIC (WS-G5482) module is not securely inserted, the switch might fail to recognize it or might display an incorrect media type following a show interface privileged EXEC command entry. If this happens, remove and reinsert the GBIC module.

Beginning with Release 12.1(11)EA1, the mac address-table aging-time command replaces the mac-address-table aging-time command (with the hyphen). The mac-address-table aging-time command (with the hyphen) will become obsolete in a future release.

Beginning with release 12.1(11)EA1, the vtp privileged EXEC command keywords are available in the vtp global configuration command. The vtp privileged EXEC command will become obsolete in a future release.

Cluster Notes

This note applies to cluster configuration:

The cluster setup privileged EXEC command and the standby mac-address interface configuration command have been removed from the CLI and the documentation because they did not function correctly.

CMS Notes

These notes apply to CMS configuration:

If you use CMS on Windows 2000, it might not apply configuration changes if the enable password is changed from the CLI during your CMS session. You have to restart CMS and enter the new password when prompted. Platforms other than Windows 2000 prompt you for the new enable password when it is changed.

CMS does not display QoS classes that are created through the CLI if these classes have multiple match statements. When using CMS, you cannot create classes that match more than one match statement. CMS does not display policies that have such classes.

If you use Internet Explorer Version 5.5 and select a URL with a nonstandard port at the end of the address (for example,, you must enter http:// as the URL prefix. Otherwise, you cannot launch CMS.

Within an ACL, you can change the sequence of ACEs that have the host keyword. However, because such ACEs are independent of each other, the change has no effect on the way the ACL filters traffic.

If you use the Netscape browser to view the CMS GUI and you resize the browser window while CMS is initializing, CMS does not resize to fit the window.

Resize the browser window again when CMS is not busy.

CMS does not start if the temporary directory on your computer runs out of memory. This problem can occur because of a bug in the 1.2.2 version of the Java plug-in. The plug-in creates temporary files in the directory whenever it runs CMS, and the directory eventually runs out of plug-in space.

The workaround is to remove all the jar_cache*.tmp files from the temporary directory. The path to the directory is different for different operating systems:

Solaris: /var/tmp
Windows NT and Windows 2000: \TEMP
Windows 95 and 98: \Windows\Temp

Read-Only Mode in CMS

CMS provides two levels of access to the configuration options. If your privilege level is 15, you have read-write access to CMS. If your privilege level is from 1 to 14, you have read-only access to CMS. In the read-only mode, some data is not displayed, and an error message appears when these switches are running these software releases:

Catalyst 2900 XL or Catalyst 3500 XL member switches running Release 12.0(5)WC2 or earlier

Catalyst 2950 member switches running Release 12.0(5)WC2 or earlier

Catalyst 3550 member switches running Release 12.1(6)EA1 or earlier

In the Front Panel view or Topology view, CMS does not display error messages. In the Front Panel view, if the switch is running one of the software releases listed previously, the device LEDs do not appear. In Topology view, if the member is a Long-Reach Ethernet (LRE) switch, the customer premises equipment (CPEs) connected to the switch do not appear. The Bandwidth and Link graphs also do not appear in these views.

To view switch information, you need to upgrade the member switch software. For information about upgrading switch software, see the "Downloading Software" section.

Open Caveats

These are the open caveats with possible unexpected activity in this IOS release:

"Open IOS Caveats" section

"Open Cluster Caveats" section

"Open CMS Caveats" section

Open IOS Caveats

These are the severity 3 IOS configuration caveats:


If a stack contains both Catalyst 3550 switches and Catalyst 3500 XL or Catalyst 2900 XL switches, cross-stack UplinkFast does not function if the management VLAN on the Catalyst 3500 XL or Catalyst 2900 XL switches is changed to other than VLAN 1 (the default).

The workaround is to make sure that the management VLAN of all Catalyst 3500 XL or 2900 XL switches in the stack is set to VLAN 1.


Multicast data might be temporarily lost when a link comes up in a redundant network and causes the reverse path forwarding (RPF) to change. This only occurs when there are multiple paths between the rendezvous point (RP) and the multicast source. If the RP loses link state on the incoming interface, it quickly fails-over to a different interface. However, if the original interface comes up again, data may be lost for about 1 minute because PIM hello packets are being dropped by the RP while the interface is coming up. If link is not lost (for example, the RP port is connected to a hub, or the path is interrupted elsewhere), the data loss does not occur.


When a Catalyst 6000 secure shell (SSH) client connects to a Catalyst 3550 SSH server, the Catalyst 6000 switch halts at the enable-password prompt from which to enter privileged EXEC mode. This problem occurs when the Catalyst 6000 switch is running the c6sup1_rp-JK2SV-M crypto-image as a client and the Catalyst 3550 switch is running the crypto-image as the SSH server.

There is no workaround.


The VLAN Query Protocol (VQP) might not work correctly when the switch has multiple switch virtual interfaces (SVIs) configured with IP addresses. If the VLAN Membership Policy Server (VMPS) does not have routes configured to reach all subnets on the Catalyst 3550 switch, it might not assign dynamic access ports on the switch to a VLAN. This is because the switch randomly selects one of the configured SVI IP addresses (instead of the IP address configured on the VLAN interface used to reach the VMPS) when it sends VQP requests to the VMPS server. The server responds with the VLAN assignment only if the IP address used in the VQP request is in the VMPS database.

The workaround is to configure the VMPS server to have routes to reach all subnets on the Catalyst 3550 switch.


The SYS-3-CPUHOG message might appear when you enter a no switchport trunk allowed vlan interface range command to remove the allowed list for all trunk ports on the switch.

The workaround is to enter the same command in the interface configuration mode for each trunk port individually.


TCAM generation might fail when there are multiple ACLs in a policy-map. If you add an entry that checks Transmission Control Protocol (TCP) flags to an access list that is used for QoS classification, the system might report that a hardware limitation has been reached for the policy map. This can occur when the policy map already contains several other access list entries that check different TCP flags, or that check TCP or User Datagram Protocol (UDP) port numbers using an operation different from equal (eq), such as not equal (ne), less than (lt), greater than (gt), or range. When the hardware limitation is reached, the service-policy input policy-map-name interface configuration command is removed from the running configuration of the interface.

Checking for TCP flags and TCP/UDP port numbers using operators other than eq share some of the same hardware resources. The switch supports no more than six checks within a single policy map. An identical check repeated in multiple entries in the same policy map counts as a single instance. If this limit is reached during a TCP or UDP port number check, the software can often work around the problem by allocating extra entries in the TCAM, but there is no workaround if the limit is reached during a check against the TCP flags in the packet. Similar checks in a port ACL applied to the same physical interface as the policy map also count toward the limit.

Because these resources are allocated on a first-come, first-serve basis, rearranging the order of ACLs within a policy map or the order of entries within a single ACL, placing the TCP flags checks as early as possible, might enable the policy map to be loaded into the hardware.

Similar limits apply for any combination of input VLAN maps, input router ACLs, output VLAN maps, and output router ACLs that share the same VLAN label. The switch supports eight checks for all features on the same VLAN label. When the limit is reached, the system might forward packets by using the CPU rather than through hardware, greatly reducing system performance. To determine the VLAN label assigned to a VLAN or interface on input or output, use the show fm vlan or show fm interface privileged EXEC commands. Then use the show fm vlan-label privileged EXEC command to determine which set of features (input VLAN map, input router ACL, output VLAN map, or output router ACL) share this label.

These are the workarounds:

Re-arrange the order of classes within the policy map and the order of entries within the individual access lists in the policy map or within any IP port ACL applied to the interface so that checks for TCP flags are made as early as possible within the policy map. This also applies to the order of the individual ACLs within a VLAN map and the order of the individual entries in a security ACL.

Add an extra entry to the front of an ACL that checks for the same TCP flags that are checked later on in the ACL. If the first entry of the ACL already matches only the TCP protocol, you can duplicate the entry and add a check for the appropriate TCP flags.

Reduce the number of different combinations of TCP flags being tested.

If the other workarounds fail, avoid combining any check against the TCP flags with gt, lt, ne, or range checks within the policy map and port ACL configured on the interface or within the VLAN maps and router ACLs that share the same VLAN label.


When you reboot the Catalyst 3550-24-FX switch, it might loop back packets received on an FX port to its link partner. This occurs before the IOS software takes control of the system and lasts for about 200 milliseconds.

As a result, the link partner might shut down the port when it detects loopback packets, or MAC addresses might get learned on the wrong ports on upstream switches. Under these conditions, the network might be unable to deliver packets to a few devices for up to 5 minutes after the Catalyst 3550-24-FX is reset:

The Catalyst 3550-24-FX switch is connected to one or more switches in the network.

Spanning tree is disabled in the network or the Port Fast feature is enabled on the ports connected to the Catalyst 3550-24-FX switch.

The Catalyst 355-24-FX switch is powered cycled or reloaded from CLI.

One or more devices in the network transmit a broadcast or multicast packet during the 200-millisecond timing window while the Catalyst 3550-24-FX switch is booting.

This problem corrects itself after 5 minutes or when these devices transmit a broadcast or multicast packet, whichever comes first.

The workaround is to enable spanning tree in the network and to make sure that the Port Fast feature is disabled on all ports connected to the Catalyst 3550-24-FX switch.


When the MAC address aging time is set for more than 10 minutes, the addresses do not age out.

The workaround is to set the MAC address aging time to less than 10 minutes.


The QoS counters remain the same after you enter the no mls qos interface configuration command.

There is no workaround.


If you apply a large ACL and it fills the entire ternary content addressable memory (TCAM), the multicast VLAN registration (MVR) IP multicast data packets are sent to the switch CPU and are not forwarded to the MVR receiver ports.

There is no workaround.


If you create a policy map by using the policy-map policy-map-name global configuration command, enter the class class-map-name policy-map configuration command and then you immediately exit from the policy-map class configuration mode, the policy map does not show its class-map association.

The workaround is to configure another command (such as the police, trust, or set policy-map class configuration command) after entering the class class-map-name policy-map configuration command.


When you change the class action of an existing per-port per-VLAN QoS policy map that is already attached to an interface, per-port per-VLAN QoS hardware entries on the switch are not modified. This is an example of such a change, where pm-vlan-1 is a per-port per-VLAN QoS policy-map and class cm-vlan-1 is an existing class in pm-vlan-1:

Switch(config)# interface fastethernet0/1
Switch(config-if)# service-policy input pm-vlan-1
Switch(config-if)# exit
Switch(config)# policy-map pm-vlan-1
Switch(config-pmap)# class cm-vlan-1
Switch(config-pmap-c)# set ip dscp 1
Switch(config-pmap-c)# end

The workaround is to detach and re-attach the policy map by entering the no service-policy input policy-map-name interface configuration command followed by the service-policy input policy-map-name command.


When the switch runs out Layer 4 operation (L4op) resources, the ACL that you are configuring or modified is not applied.

There is no workaround.


When you configure a cascaded stack of switches by using the GigaStack GBIC module link between a Catalyst 3550-12G and a Catalyst 3524XL, the connection could fail.

The workaround is to configure all Gigabit ports as trunk ports by using the switchport mode trunk and switchport trunk encapsulation dot1q interface configuration commands.


A Catalyst 3550 switch per-port per-VLAN QoS traffic classification might fail if the hardware resource limit is reached. When you try to attach a per-port per-VLAN QoS policy map to an interface, exceeding the hardware resource limit, this syslog message appears:

QoS: Programming TCAM failed: Not enough TCAM entries

This means that the specific policy map has VLAN entries overlapped with existing policy maps already attached to other interfaces.

The workaround is to not attach per-port per-VLAN QoS policy maps that could result in reaching the hardware resource limit. If this has already occurred, then detach and re-attach the other policy maps in the system by entering the no service-policy input policy-map-name interface configuration command followed by the service-policy input policy-map-name interface configuration command.


If you try to attach a a large per-port per-VLAN QoS policy map with many classes to an interface, the Catalyst 3550 switch might generate this syslog message:

%SYS-3-CPUHOG: Task ran for xxxx msec (4/4), process = Exec, PC = yyyy. -Traceback=... 

This can occur when the policy map has more than 128 classes and the VLANs in the classes overlap.

The workaround is to modify the policy map so that there are fewer classes or so that fewer classes have overlapping VLANs.


The switch utilization might be unusually high when you try to remove a match criteria common to per-port per-VLAN QoS policy-maps that are already attached to interfaces. These policy-maps have a large number of VLANs specified in the match clauses.

The workaround is to detach the policy-maps from the interfaces, change the match clause, and then re-attach the policy-map to the interfaces.


When a community string is assigned by the cluster command switch, you cannot get any dot1dBridge MIB objects using a community string with a VLAN entity from a cluster member switch.

The workaround is to manually add the cluster community string with the VLAN entity on the member switches for all active VLANs shown in the show spanning-tree summary display. This is an example of such a change, where cluster member 3 has spanning-tree on vlan 1-3 and the cluster commander community string is public@es3.

Mbr3(config)#snmp community public@es3@1 RO
Mbr3(config)#snmp community public@es3@2 RO
Mbr3(config)#snmp community public@es3@3 RO


When a switch is first turned on, it can obtain an IP address from a DHCP server. When the switch is restarted with the service configuration option, if there is a configuration file in nonvolatile RAM, it does not attempt to get an IP address from a DHCP server.

The workaround is to manually assign an IP address to the switch.


When you start a switch that has a configured Switch Port Analyzer (SPAN) or RSPAN session, all traffic on monitored trunk ports is mirrored to the SPAN or RSPAN destination, even if the session is configured to filter VLANs on source trunk ports.

The workaround is to start the switch and remove the VLAN filer by using the no monitor session session_number filter vlan vlan-id global configuration command. Then re-enter the command to establish VLAN filtering.


Having more than 16 HSRP groups configured and active on the switch might not provide fail-over protection for all groups.

The workaround is to not have more than 16 configured or active HSRP groups on the switch. Or, at a minimum, do not have more than 16 HSRP groups active at the same time.

Open Cluster Caveats

These are the severity 3 cluster configuration caveats:


When you enter a remote command on a Catalyst 3550 member switch from a command switch that is not a Catalyst 3550 switch, if the command generates a lot of output and the output is paused and restarted, communication between the two switches might halt.

The workaround is to follow the documented cluster configuration guidelines, which recommend using a Catalyst 3550 switch as the command switch in mixed-model clusters.


When Catalyst 1900, 2820, or 2900 XL 4 MB series switches are participating in a cluster and the active command switch fails and then is restored after the standby command switch has updated the members, it is possible for these legacy switches to miss the restoration and retain the standby command switch's MAC address.

The workaround is to manually reset the command switch MAC address on each member switch.

Open CMS Caveats

These are the severity 3 CMS configuration caveats:


If you click the list of switches in CMS and press the Page Down key on the keyboard, the entire list moves to the bottom of the window. This only happens with Windows NT.

The workaround is to collapse the list into a single icon, which returns the list to the top of the window.


If you use the command switch Domain Name System (DNS) server name to start CMS for a member that is running an earlier software release than the command switch, CMS might not display the switch image, or it might display the command switch image. This can also occur when a standby group is configured for a cluster and you access CMS by entering the command-switch IP address and not the virtual IP address.

The workaround is to always use the command-switch IP address to access CMS. If a standby group is configured for a cluster, always use the virtual IP address to access CMS.


The CMS Time Management window supports the configuration of the Network Time Protocol (NTP) and system time. When you make changes on this window from a command switch, Java propagates the changes to all cluster members. A conflict can arise if you configure NTP and also use the Set Daylight Saving Time and Set Current Time tabs.

To avoid a possible conflict, either set the system time for the entire cluster on the command switch, or configure NTP on the command switch to use an NTP server to provide time to the cluster. Do not use both methods at the same time.


If you try to enable Port Fast on an interface that does not accept it—a trunk port, for example—no message warns you that Port Fast was not enabled.

There is no workaround.


If you select multiple FastEthernet ports on a Catalyst 3550 switch, the speed of 1000 Mbps is shown as an option in the Modify Port Settings window. Ignore this speed option.


You cannot modify the multicast groups that are shown in the IGMP Snooping window.

The workaround is to delete the group that you want to modify and then recreate it with the change that you want.


You cannot switch modes (for example, from Guide Mode to Expert Mode) for an open CMS window.

The workaround is to close the open window, select the mode that you want, and then reopen the CMS window.

Note For the mode change to take effect on any other CMS window that is open, you need to close that window and then reopen it after you select the new mode.


If both a port ACL and a VLAN map are already configured on the Catalyst 3550 switch and you try to attach a port ACL through the CMS Security Wizard, you can use the Security Wizard to attach the port ACL to a switch port. The attached port ACL conflicts with the existing VLAN map and this is not a allowed configuration.

The workaround is to verify that both a port ACL and a VLAN map are not configured on the switch before using the Security Wizard.


The data that is displayed by using the Stack Bar and Stack Area options in the Link Graph window is incorrect.

The workaround is to use the Line, Bar, or Area options instead.


In read-only mode, time ranges are not displayed. See the "Read-Only Mode in CMS" section for more information about CMS modes.

There is no workaround.


You cannot add a switch that does not have Terminal Access Control Access System Plus (TACACS+) configured on it to a cluster if all the other cluster members are configured with TACACS+.

The workaround is to configure TACACS+ on the switch before adding it to the cluster.


The cursor is not displayed in the text-entering areas in CMS. However, in some cases you can still enter text. This problem occurs with certain combinations of both the browser and the Java Plug-In. For example, it can occur when Netscape Communicator 6.2.3 is used with Java Plug-In 1.3.1_02 or 1.3.1_03.

These are the workarounds:

Use a supported browser and Java Plug-In. For more information, see the "Software Compatibility" section.

Click in a text-entering area outside CMS, such as in the browser. Make sure that the cursor appears, and then click in the text-entering area in CMS. The cursor should now appear. If it does not, restart CMS by clicking on the reload/refresh button or by restarting the browser.


If you try to create a time-range entry that specifies multiple days with the same time, CMS displays only the first day in the list of days. This is an example of such a time-range entry:

periodic Monday Wednesday Friday 8:00 to 17:00.

The periodic time-range entries with specific days use this syntax:

periodic Monday 8:00 to Tuesday 17:00.


periodic Monday 8:00 to Monday 17:00

The workaround is to create a specific time-range entry for each day.


When a Catalyst 3550 switch becomes a command switch, it automatically creates an IP extended ACL called CMP-NAT-ACL that specifies a set of IP addresses subject to cluster-NAT address translation. Although CMS allows you to modify or delete this ACL, do not modify or delete this ACL.

There is no workaround.


A red border appears around the text-entering area of some CMS dialogs. The color of the border changes to green when text is entered. This is only a cosmetic error. The colored border does not prevent you from entering text.

There is no workaround.

Note This error only occurs with Java plug-in 1.4.0.


When there are no CMS windows open, the CMS keyboard shortcuts do not work.

The workaround is to leave one CMS window open. For example, leave the Help > About window open.

Resolved Caveats

These are the caveats that have been resolved in this release.

"Resolved IOS Caveats" section

"Resolved CMS Caveats" section

Resolved IOS Caveats

These IOS caveats were resolved in Release 12.1(11)EA1:


When applied to routed ports, configurations for these two keywords are now retained after a reboot:

the tunnel keyword relating to IP multicast routing, such as the tunnel number, tunnel source ip-address, and tunnel destination ip-address interface configuration commands

the HSRP track keyword in the standby group-number track type number [interface-priority] interface configuration commands.


When you change connections between GigaStack ports, the link is now correctly established.


When you use the ip-access group or mac-access group interface configuration command to apply a port ACL to a physical Layer 2 interface that is a member of an EtherChannel, the command is no longer accepted. The switch does not support port ACLs on an EtherChannel or an interface belonging to an EtherChannel.


When you enter the clear adjacency privileged EXEC command to clear the adjacency table and the clear ip route * privileged EXEC command to remove all routing table entries, a SYS-3-CPUHOG error message no longer appears.


If two separate HSRP groups are misconfigured with the same standby IP address, an ARP storm no longer occurs.


When you attempt an SNMP GetNext operation to retrieve the value of the cIgmpFilterEditSpinLock object in the CISCO-IGMP-FILTER-MIB, the object ID (OID) returned by the switch is now an IGMP Filter Editor Group object.


If you create multiple loopback interfaces by using the loopback interface 0 global configuration command, you can now delete the loopback interfaces by using the no interface loopback 0 command.


When you change the spanning-tree mode from MST to PVST and the number of VLANs is greater than 128, the traffic is now forwarded on VLANs for which the spanning-tree instance is not created (the maximum number of spanning-tree instance is 128).


If one or more ports are configured in half-duplex mode and you enter the switchport or no switchport interface configuration command for a single interface or for a range of interfaces, the switch no longer fails.


The Network Time Protocol (NTP) handling is improved.


The authentication, authorization, and accounting (AAA) authentication process has been corrected.


The Response Time Reporter (RTR) packet handling process is improved.


Spanning-tree BPDU destination MAC addresses are now sent to the correct destination addresses.

Resolved CMS Caveats

This CMS caveat was resolved in Release 12.1(11)EA1:


In the CMS QoS Policies window, the Attach tab now shows egress policy information. When some interfaces have an egress QoS policy associated with them, the policy now appears in the Egress Policy column of the table of attached QoS policies.

Documentation Updates

You can access all Catalyst 3550 documentation at this URL:

This section provides updates to the product documentation. These changes will be included in the next version of the documentation.


These are corrections for the Catalyst 3550 Multilayer Switch Software Configuration Guide:

In the section "Standard QoS Configuration Guidelines" on page 27-19, this information was omitted:

Do not use the show policy-map interface privileged EXEC command to display classification information for incoming traffic. The interface keyword is not supported, and the statistics shown in the display should be ignored. Instead, you should specify the DSCPs to be monitored by using the mls qos monitor dscp dscp1 ... dscp8 interface configuration command, and then you should use the show mls qos interface interface-id statistics privileged EXEC command. For more information about these commands, refer to the Catalyst 3550 Multilayer Switch Command Reference.

In the section "Classifying Traffic on a Per-Port Per-VLAN Basis By Using Class Maps" on page 27-34, this information was omitted:

With per-port per-VLAN classification, unmatched VLANs are treated similarly to the default class, which means that the unmatched VLANs share the remaining bandwidth. You cannot modify this default-class behavior. If necessary, you can use VLAN map filters to block these VLANs.

These are corrections for the Catalyst 3550 Multilayer Switch Hardware Installation Guide:

The guide incorrectly states that the Catalyst 3550-24-DC switch ships with two, 23-inch rack-mounting brackets. The Catalyst 3550-24-DC switch ships with two, 19-inch rack-mounting brackets.

In the guide, Figure 2-28 shows an incorrect voltage label on the rear-panel of the Catalyst 3550-24-DC switch. This is the correct label:

Related Documentation

These documents provide complete information about the switch and are available from this site:

You can order printed copies of documents with a DOC-xxxxxx= number from the sites and from the telephone numbers listed in the "Ordering Documentation" section.

Catalyst 3550 Multilayer Switch Software Configuration Guide (order number DOC-7811194=)

Catalyst 3550 Multilayer Switch Command Reference (order number DOC-7811195=)

Catalyst 3550 Multilayer Switch System Message Guide (order number DOC-7811196=)

Cluster Management Suite (CMS) online help (available only from the switch CMS software)

Catalyst 3550 Multilayer Switch Hardware Installation Guide (order number DOC-7811358=)

1000BASE-T Gigabit Interface Converter Installation Note (not orderable but is available on

Catalyst GigaStack Gigabit Interface Converter Hardware Installation Guide (order number DOC-786460=)

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