Information About Interface Characteristics
The following sections provide information about interface characteristics.
Interface Types
This section describes the different types of interfaces supported by the device. The rest of the chapter describes configuration procedures for physical interface characteristics.
Port-Based VLANs
A VLAN is a switched network that is logically segmented by function, team, or application, without regard to the physical location of the users. Packets received on a port are forwarded only to ports that belong to the same VLAN as the receiving port. Network devices in different VLANs cannot communicate with one another without a Layer 3 device to route traffic between the VLANs.
VLAN partitions provide hard firewalls for traffic in the VLAN, and each VLAN has its own MAC address table. A VLAN comes into existence when a local port is configured to be associated with the VLAN, when the VLAN Trunking Protocol (VTP) learns of its existence from a neighbor on a trunk, or when a user creates a VLAN.
To configure VLANs, use the vlan vlan-id global configuration command to enter VLAN configuration mode. The VLAN configurations for normal-range VLANs (VLAN IDs 1 to 1005) are saved in the VLAN database. If VTP is version 1 or 2, to configure extended-range VLANs (VLAN IDs 1006 to 4094), you must first set VTP mode to transparent. Extended-range VLANs created in transparent mode are not added to the VLAN database but are saved in the running configuration. With VTP version 3, you can create extended-range VLANs in client or server mode in addition to transparent mode. These VLANs are saved in the VLAN database.
Add ports to a VLAN by using the switchport command in interface configuration mode.
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Identify the interface.
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For a trunk port, set trunk characteristics, and, if desired, define the VLANs to which it can belong.
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For an access port, set and define the VLAN to which it belongs.
Switch Ports
Switch ports are Layer 2-only interfaces associated with a physical port. Switch ports belong to one or more VLANs. A switch port can be an access port or a trunk port. You can configure a port as an access port or trunk port or let the Dynamic Trunking Protocol (DTP) operate on a per-port basis to set the switchport mode by negotiating with the port on the other end of the link. Switch ports are used for managing the physical interface and associated Layer 2 protocols and do not handle routing or bridging.
Configure switch ports by using the switchport interface configuration commands.
Access Ports
An access port belongs to and carries the traffic of only one VLAN (unless it is configured as a voice VLAN port). Traffic is received and sent in native formats with no VLAN tagging. Traffic arriving on an access port is assumed to belong to the VLAN assigned to the port. If an access port receives a tagged packet (Inter-Switch Link [ISL] or IEEE 802.1Q tagged), the packet is dropped, and the source address is not learned.
The types of access ports supported are:
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Static access ports are manually assigned to a VLAN (or through a RADIUS server for use with IEEE 802.1x.
You can also configure an access port with an attached Cisco IP Phone to use one VLAN for voice traffic and another VLAN for data traffic from a device attached to the phone.
Trunk Ports
A trunk port carries the traffic of multiple VLANs and by default is a member of all VLANs in the VLAN database. The IEEE 802.1Q trunk port type is supported. An IEEE 802.1Q trunk port supports simultaneous tagged and untagged traffic. An IEEE 802.1Q trunk port is assigned a default port VLAN ID (PVID), and all untagged traffic travels on the port default PVID. All untagged traffic and tagged traffic with a NULL VLAN ID are assumed to belong to the port default PVID. A packet with a VLAN ID equal to the outgoing port default PVID is sent untagged. All other traffic is sent with a VLAN tag.
Although by default, a trunk port is a member of every VLAN known to the VTP, you can limit VLAN membership by configuring an allowed list of VLANs for each trunk port. The list of allowed VLANs does not affect any other port but the associated trunk port. By default, all possible VLANs (VLAN ID 1 to 4094) are in the allowed list. A trunk port can become a member of a VLAN only if VTP knows of the VLAN and if the VLAN is in the enabled state. If VTP learns of a new, enabled VLAN and the VLAN is in the allowed list for a trunk port, the trunk port automatically becomes a member of that VLAN and traffic is forwarded to and from the trunk port for that VLAN. If VTP learns of a new, enabled VLAN that is not in the allowed list for a trunk port, the port does not become a member of the VLAN, and no traffic for the VLAN is forwarded to or from the port.
Tunnel Ports
Tunnel ports are used in IEEE 802.1Q tunneling to segregate the traffic of customers in a service-provider network from other customers who are using the same VLAN number. You configure an asymmetric link from a tunnel port on a service-provider edge switch to an IEEE 802.1Q trunk port on the customer switch. Packets entering the tunnel port on the edge switch, already IEEE 802.1Q-tagged with the customer VLANs, are encapsulated with another layer of an IEEE 802.1Q tag (called the metro tag), containing a VLAN ID unique in the service-provider network, for each customer. The double-tagged packets go through the service-provider network keeping the original customer VLANs separate from those of other customers. At the outbound interface, also a tunnel port, the metro tag is removed, and the original VLAN numbers from the customer network are retrieved.
Tunnel ports cannot be trunk ports or access ports and must belong to a VLAN unique to each customer.
Routed Ports
A routed port is a physical port that acts like a port on a router; it does not have to be connected to a router. A routed port is not associated with a particular VLAN, as is an access port. A routed port behaves like a regular router interface, except that it does not support VLAN subinterfaces. Routed ports can be configured with a Layer 3 routing protocol. A routed port is a Layer 3 interface only and does not support Layer 2 protocols, such as DTP and STP.
Configure routed ports by putting the interface into Layer 3 mode with the no switchport interface configuration command. Then assign an IP address to the port, enable routing, and assign routing protocol characteristics by using the ip routing and router protocol global configuration commands.
Note |
Entering a no switchport interface configuration command shuts down the interface and then re-enables it, which might generate messages on the device to which the interface is connected. When you put an interface that is in Layer 2 mode into Layer 3 mode, the previous configuration information related to the affected interface might be lost. |
The number of routed ports that you can configure is not limited by software. However, the interrelationship between this number and the number of other features being configured might impact CPU performance because of hardware limitations.
Switch Virtual Interfaces
A switch virtual interface (SVI) represents a VLAN of switch ports as one interface to the routing function in the system. You can associate only one SVI with a VLAN. You configure an SVI for a VLAN only to route between VLANs or to provide IP host connectivity to the device. By default, an SVI is created for the default VLAN (VLAN 1) to permit remote device administration. Additional SVIs must be explicitly configured.
Note |
You cannot delete interface VLAN 1. |
SVIs provide IP host connectivity only to the system. SVIs are created the first time that you enter the vlan interface configuration command for a VLAN interface. The VLAN corresponds to the VLAN tag associated with data frames on an ISL or IEEE 802.1Q encapsulated trunk or the VLAN ID configured for an access port. Configure a VLAN interface for each VLAN for which you want to route traffic, and assign it an IP address.
You can also use the interface range command to configure existing VLAN SVIs within the range. The commands entered under the interface range command are applied to all existing VLAN SVIs within the range. You can enter the command interface range create vlan x - y to create all VLANs in the specified range that do not already exist. When the VLAN interface is created, interface range vlan id can be used to configure the VLAN interface.
Although the device supports a total of 1005 VLANs and SVIs, the interrelationship between the number of SVIs and routed ports and the number of other features being configured might impact CPU performance because of hardware limitations.
When you create an SVI, it does not become active until it is associated with a physical port.
EtherChannel Port Groups
EtherChannel port groups treat multiple switch ports as one switch port. These port groups act as a single logical port for high-bandwidth connections between devices or between devices and servers. An EtherChannel balances the traffic load across the links in the channel. If a link within the EtherChannel fails, traffic previously carried over the failed link changes to the remaining links. You can group multiple trunk ports into one logical trunk port, group multiple access ports into one logical access port, group multiple tunnel ports into one logical tunnel port, or group multiple routed ports into one logical routed port. Most protocols operate over either single ports or aggregated switch ports and do not recognize the physical ports within the port group. Exceptions are the DTP, the Cisco Discovery Protocol (CDP), and the Port Aggregation Protocol (PAgP), which operate only on physical ports.
When you configure an EtherChannel, you create a port-channel logical interface and assign an interface to the EtherChannel. For Layer 3 interfaces, you manually create the logical interface by using the interface port-channel global configuration command. Then you manually assign an interface to the EtherChannel by using the channel-group interface configuration command. For Layer 2 interfaces, use the channel-group interface configuration command to dynamically create the port-channel logical interface. This command binds the physical and logical ports together.
Network Modules
The device supports two network modules that include10-Gigabit Ethernet and 40-Gigabit Ethernet uplink ports. Though they are named Ethernet, all ports are only fiber ports.
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8x10G
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2x40G
Using the Switch USB Ports
The has two USB ports on the front panel — a USB mini-Type B console port and a USB 2.0 host port and a USB 3.0 port on the rear panel. Note that C9500-32C, C9500-32QC, C9500-48Y4C, and C9500-24Y4C models of the Cisco Catalyst 9500 Series Switches do not have a USB port on the rear.
USB Mini-Type B Console Port
The device has the following console ports:
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USB mini-Type B console connection
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RJ-45 console port
Console output appears on devices connected to both ports, but console input is active on only one port at a time. By default, the USB connector takes precedence over the RJ-45 connector.
Note |
Windows PCs require a driver for the USB port. See the hardware installation guide for driver installation instructions. |
Use the supplied USB Type A-to-USB mini-Type B cable to connect a PC or other device to the device. The connected device must include a terminal emulation application. When the device detects a valid USB connection to a powered-on device that supports host functionality (such as a PC), input from the RJ-45 console is immediately disabled, and input from the USB console is enabled. Removing the USB connection immediately reenables input from the RJ-45 console connection. An LED on the device shows which console connection is in use.
Console Port Change Logs
At software startup, a log shows whether the USB or the RJ-45 console is active. Every device always first displays the RJ-45 media type.
In the sample output, device 1 has a connected USB console cable. Because the bootloader did not change to the USB console, the first log from the device shows the RJ-45 console. A short time later, the console changes and the USB console log appears.
switch-1
*Mar 1 00:01:00.171: %USB_CONSOLE-6-MEDIA_RJ45: Console media-type is RJ45.
*Mar 1 00:01:00.431: %USB_CONSOLE-6-MEDIA_USB: Console media-type is USB.
When the USB cable is removed or the PC de-activates the USB connection, the hardware automatically changes to the RJ-45 console interface:
You can configure the console type to always be RJ-45, and you can configure an inactivity timeout for the USB connector.
USB 2.0 Host Port
The USB 2.0 host port provides access to external USB flash devices, also known as thumb drives or USB keys. The port supports Cisco USB flash drives with capacities from 128 MB to 16 GB (USB devices with port densities of 128 MB, 256 MB, 1 GB, 4 GB, 8 GB, and 16 GB are supported). You can use standard Cisco IOS command-line interface (CLI) commands to read, write, erase, and copy to or from the flash device. You can also configure the device to boot from the USB flash drive.
Interface Connections
Devices within a single VLAN can communicate directly through any switch. Ports in different VLANs cannot exchange data without going through a routing device. With a standard Layer 2 device, ports in different VLANs have to exchange information through a router. By using the device with routing enabled, when you configure both VLAN 20 and VLAN 30 with an SVI to which an IP address is assigned, packets can be sent from Host A to Host B directly through the device with no need for an external router.
When the Network Advantage license is used on the device or the active device, the device uses the routing method to forward traffic between interfaces. If the Network Essentials license is used on the device or the active device, only basic routing (static routing and RIP) is supported. Whenever possible, to maintain high performance, forwarding is done by the device hardware. However, only IPv4 packets with Ethernet II encapsulation are routed in hardware.
The routing function can be enabled on all SVIs and routed ports. The device routes only IP traffic. When IP routing protocol parameters and address configuration are added to an SVI or routed port, any IP traffic received from these ports is routed.
Interface Configuration Mode
The device supports these interface types:
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Physical ports: Device ports and routed ports
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VLANs: Switch virtual interfaces
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Port channels: EtherChannel interfaces
You can also configure a range of interfaces.
To configure a physical interface (port), specify the interface type, module number, and device port number, and enter interface configuration mode.
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Type: FortyGigabitEthernet (fortygigabitethernet or fo) fiber ports.
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Switch number: The number that identifies the given device. The number range is assigned the first time the device initializes.
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Module number: The module or slot number on the device: switch (downlink) ports are 0, and uplink ports are 1.
Note
C9500-32C, C9500-32QC, C9500-48Y4C, and C9500-24Y4C models of the Cisco Catalyst 9500 Series Switches have their Module number as 0 always.
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Port number: The interface number on the device. The 10/100/1000 port numbers always begin at 1, starting with the far left port when facing the front of the device, for example, FortyGigabitEthernet1/0/1 or FortyGigabitEthernet1/0/8.
On a device with SFP uplink ports, the module number is 1 and the port numbers restart. For example, if the device has 24 10/100/1000 ports, the SFP module ports are GigabitEthernet1/1/1 through GigabitEthernet1/1/4 or TenGigabitEthernet1/1/1 through TenGigabitEthernet1/1/4.
You can identify physical interfaces by physically checking the interface location on the device. You can also use the show privileged EXEC commands to display information about a specific interface or all the interfaces on the switch. The remainder of this chapter primarily provides physical interface configuration procedures.
These are examples of how to configure interfaces on standalone device:
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To configure 40-G port 4 on a standalone device, enter this command:
Device# configure terminal Device(config)# interface FortyGigabitEthernet1/0/4
Breakout Interfaces
Cisco Catalyst 9500 Series Switches support breakout cables. These cables support 4x10 G by enabling a single 40-G QSFP+ interface to be split into four 10-G SFP+ interfaces and a single 100-G QSFP28 interface into four 25-G SFP28 interfaces. Starting with Cisco IOS XE Gibraltar 16.11.1, support for breakout cables is enabled for Cisco Catalyst 9500 Series Switches - High Performance with Cisco StackWise Virtual.
Note |
Breakout cable support is available only on the following switch models and network modules, with a few limitations. |
Switch Models
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C9500-12Q
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C9500-24Q
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C9500-40X-2Q
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C9500-16X-2Q
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C9500-32C
Network Modules
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C9500-NM-2Q
Limitations for Breakout Interfaces
Catalyst 9500 Series Switches
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To enable breakout for dual mode QSFP breakout cables, the hw-module breakout module slot port port-range switch switch-num command must be configured on all the ports of the switch. The range for the variables in the hw-module breakout module slot port port-range switch switch-num command are given below:
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slot — Slot number of port depending on the chassis model.
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port-range — Single port or range of ports on which breakout is configured. The range varies from 1 to 24.
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switch-num — Switch number in the stack. The range varies from 1 to 8.
See Configuring a Breakout Interface for the list of configurable interfaces.
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When Cisco StackWise Virtual is configured, breakout ports using 4X10G breakout cables can only be used as data ports; they cannot be used to configure StackWise Virtual links (SVLs) or dual-active detective (DAD) links.
Catalyst 9500 Series Switches - High Performance
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Breakout is supported only on 24 ports of the C9500-32C switch model. Every 4th port of C9500-32C does not support breakout due to ASIC limitation. Port numbers 4, 8, 12, 16, 20, 24, 28 and 32 — Hu1/0/4, Hu1/0/8, Hu1/0/12, Hu1/0/16, Hu1/0/20, Hu1/0/24, Hu1/0/28 and Hu1/0/32 — do not support breakout.
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Parent port is disabled after breakout is enabled on it but configuration on the parent port is saved.
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Breakout ports appear in the output of show run , show interface status , show ip interface brief and other show and configuration commands once breakout is enabled and they are automatically removed from all the show and configuration CLIs when breakout is disabled.
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When Cisco StackWise Virtual is configured, breakout ports using 4X25G and 4X10G breakout cables can only be used as data ports; they cannot be used to configure SVLs or DAD links.
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LED of the physical port on which breakout is enabled turns green if any one of the four breakout link is up but it turns off only when all the four breakout links are down.
See Configuring a Breakout Interface for the list of configurable interfaces.
Default Ethernet Interface Configuration
To configure Layer 2 parameters, if the interface is in Layer 3 mode, you must enter the switchport interface configuration command without any parameters to put the interface into Layer 2 mode. This shuts down the interface and then re-enables it, which might generate messages on the device to which the interface is connected. When you put an interface that is in Layer 3 mode into Layer 2 mode, the previous configuration information related to the affected interface might be lost, and the interface is returned to its default configuration.
Note |
Starting from Cisco IOS XE Gibraltar 16.11.1, the C9500-32C, C9500-32QC, C9500-48Y4C, and C9500-24Y4C models of the Cisco Catalyst 9500 Series Switches bootup with interfaces in the default Layer 2 state. In all earlier releases, the default is Layer 3. (For all other models of the Cisco Catalyst 9500 Series Switches, the default interface continues to be Layer 2) The default switchport mode for all Ethernet interfaces is dynamic auto for C9500-32C, C9500-32QC, C9500-48Y4C, and C9500-24Y4C models of the Cisco Catalyst 9500 Series Switches |
This table shows the Ethernet interface default configuration, including some features that apply only to Layer 2 interfaces.
Feature |
Default Setting |
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Operating mode |
Layer 2 or switching mode (switchport command) for C9500-12Q-E, C9500-12Q-A, C9500-24Q-E, C9500-24Q-A, C9500-40X-E, and C9500-40X-A models of the Cisco Catalyst 9500 Series Switches. Layer 3 or routed port for C9500-32C, C9500-32QC, C9500-48Y4C, and C9500-24Y4C models of the Cisco Catalyst 9500 Series Switches |
Allowed VLAN range |
VLANs 1 to 4094. |
Default VLAN (for access ports) |
VLAN 1 (Layer 2 interfaces only). |
Native VLAN (for IEEE 802.1Q trunks) |
VLAN 1 (Layer 2 interfaces only). |
VLAN trunking |
Switchport mode dynamic auto (supports DTP) (Layer 2 interfaces only). |
Port enable state |
All ports are enabled. |
Port description |
None defined. |
Speed |
Autonegotiate. (Not supported on the 40-Gigabit interfaces.) The C9500-32C, C9500-32QC, C9500-48Y4C, and C9500-24Y4C models of the Cisco Catalyst 9500 Series Switches do not support autonegotiate. Their speed is determined by the type of transceiver module plugged in. |
Duplex mode |
Autonegotiate. (Not supported on the 40-Gigabit interfaces.) The C9500-32C, C9500-32QC, C9500-48Y4C, and C9500-24Y4C models of the Cisco Catalyst 9500 Series Switches support full duplex mode. |
Flow control |
Flow control is set to receive: on . It is always off for sent packets. |
EtherChannel (PAgP) |
Disabled on all Ethernet ports. |
Port blocking (unknown multicast and unknown unicast traffic) |
Disabled (not blocked) (Layer 2 interfaces only). |
Broadcast, multicast, and unicast storm control |
Disabled. |
Protected port |
Disabled (Layer 2 interfaces only). |
Port security |
Disabled (Layer 2 interfaces only). |
Port Fast |
Disabled. |
Auto-MDIX |
Enabled. |
Interface Speed and Duplex Mode
The ethernet interfaces operate at full duplex mode. In full-duplex mode, two stations can send and receive traffic at the same time.
The following table lists the modules and the speed at which they operate.
Module |
Speed with Transceiver Module Plugged in |
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C9500-32QC |
40G, or 100G with a QSFP transceiver module, or 10G with CVR-QSFP-SFP10G transceiver module. |
C9500-32C |
40G,or 100G with a QSFP transceiver module, or 10G with CVR-QSFP-SFP10G transceiver module. |
C9500-48Y4C |
1G with SFP module,10G with SFP+ module, 25G with QSFP28 module, 40G and 100G with QSFP module |
C9500-24Y4C |
1G with SFP module, 10G with SFP+ module, 25G with QSFP28 module, 40G and 100G with QSFP module. |
Note |
SFP, SFP+ and SFP28 ports support speed (auto/10/100/100) and duplex (auto/full/half) options only if the 1000Base-T SFP or the GLC-GE-100FX modules are used. |
IEEE 802.3x Flow Control
Flow control enables connected Ethernet ports to control traffic rates during congestion by allowing congested nodes to pause link operation at the other end. If one port experiences congestion and cannot receive any more traffic, it notifies the other port by sending a pause frame to stop sending until the condition clears. Upon receipt of a pause frame, the sending device stops sending any data packets, which prevents any loss of data packets during the congestion period.
Note |
The switch ports can receive, but not send, pause frames. |
You use the flowcontrol interface configuration command to set the interface’s ability to receive pause frames to on, off, or desired. The default state is on.
When set to desired, an interface can operate with an attached device that is required to send flow-control packets or with an attached device that is not required to but can send flow-control packets.
These rules apply to flow control settings on the device:
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receive on (or desired ): The port cannot send pause frames but can operate with an attached device that is required to or can send pause frames; the port can receive pause frames.
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receive off : Flow control does not operate in either direction. In case of congestion, no indication is given to the link partner, and no pause frames are sent or received by either device.
Note |
For details on the command settings and the resulting flow control resolution on local and remote ports, see the flowcontrol interface configuration command in the command reference for this release. |
Layer 3 Interfaces
The device supports these types of Layer 3 interfaces:
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SVIs: You should configure SVIs for any VLANs for which you want to route traffic. SVIs are created when you enter a VLAN ID following the interface vlan global configuration command. To delete an SVI, use the no interface vlan global configuration command. You cannot delete interface VLAN 1.
Note
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When you create an SVI, it does not become active until it is associated with a physical port.
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SVI MAC addresses do not change after a device reload. This is expected behavior.
When configuring SVIs, you can use the switchport autostate exclude command on a port to exclude that port from being included in determining SVI line-state. To disable autostate on the SVI, use the no autostate command on the SVI.
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Routed ports: Routed ports are physical ports configured to be in Layer 3 mode by using the no switchport interface configuration command. A routed port supports VLAN subinterfaces.
VLAN subinterface: A 802.1Q VLAN subinterface is a virtual Cisco IOS interface that is associated with a VLAN id on a routed physical interface. The parent interface is a physical port. Subinterfaces can be created only on Layer 3 physical interfaces. A subinterface can be associated with different functionalities such as IP addressing, forwarding policies, Quality of Service (QoS) policies, and security policies. Subinterfaces divide the parent interface into two or more virtual interfaces on which you can assign unique Layer 3 parameters such as IP addresses and dynamic routing protocols. The IP address for each subinterface should be in a different subnet from any other subinterface on the parent interface.
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Layer 3 EtherChannel ports: EtherChannel interfaces made up of routed ports.
A Layer 3 device can have an IP address assigned to each routed port and SVI.
There is no defined limit to the number of SVIs and routed ports that can be configured in a device or in a device stack. However, the interrelationship between the number of SVIs and routed ports and the number of other features being configured might have an impact on CPU usage because of hardware limitations. If the device is using its maximum hardware resources, attempts to create a routed port or SVI have these results:
-
If you try to create a new routed port, the device generates a message that there are not enough resources to convert the interface to a routed port, and the interface remains as a switchport.
-
If you try to create an extended-range VLAN, an error message is generated, and the extended-range VLAN is rejected.
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If the device is notified by VLAN Trunking Protocol (VTP) of a new VLAN, it sends a message that there are not enough hardware resources available and shuts down the VLAN. The output of the show vlan user EXEC command shows the VLAN in a suspended state.
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If the device attempts to boot up with a configuration that has more VLANs and routed ports than hardware can support, the VLANs are created, but the routed ports are shut down, and the device sends a message that this was due to insufficient hardware resources.
Note |
All Layer 3 interfaces require an IP address to route traffic. This procedure shows how to configure an interface as a Layer 3 interface and how to assign an IP address to an interface: If the physical port is in Layer 2 mode (the default), you must enter the no switchport interface configuration command to put the interface into Layer 3 mode. Entering a no switchport command disables and then re-enables the interface, which might generate messages on the device to which the interface is connected. Furthermore, when you put an interface that is in Layer 2 mode into Layer 3 mode, the previous configuration information related to the affected interface might be lost, and the interface is returned to its default configuration. |