Q. What are the Cisco
® 3750-E Series Switches?
A. The Cisco Catalyst 3750-E Series Switches with StackWise Plus are an enterprise-class line of stackable wiring closet switches that facilitates the deployment of secure converged applications while maximizing investment protection for evolving network and application requirements. Combining 10/100/1000 and PoE (PoE) configurations with 10 Gigabit Ethernet uplinks, the Cisco Catalyst 3750-E enhances worker productivity by enabling applications such as IP telephony, wireless, and video.
Cisco Catalyst 3750-E Series Key Features
• Cisco TwinGig converter module for migrating uplinks from Gigabit Ethernet to 10 Gigabit Ethernet
• PoE configurations with 15.4W of PoE on all 48 ports
• StackWise Plus for ease of use and resiliency with up to 64 Gbps of throughput
• Modular power supply with externally available backup
• Multicast routing, IPv6 routing, and access control list (ACL) in hardware
• Out-of-band Ethernet management port along with RS-232 console port
Q. What software feature set do the Cisco Catalyst 3750-E Series Switches support?
A. The Cisco Catalyst 3750-E series switches come with a universal image. Customers can activate IP Base or IP Services feature set within that universal image through software activation. Software activation authorizes and activates the Cisco IOS Software feature set. A special file contained in the switch, called a license file, is examined by Cisco IOS Software when the switch is powered on. Based on the license's type, Cisco IOS Software activates the appropriate feature set.
The IP Base feature set enables Layer 2 forwarding, high-availability, QoS and security features along with basic Layer 3 routing, including EIGRP stub mode.
The IP Services feature set enables a richer set of enterprise-class features, including:
• Dynamic routing protocols:
– Open Shortest Path First (OSPF)
– Enhanced IGRP (EIGRP)
– Border Gateway Protocol Version 4 (BGPv4)
• Policy-based routing (PBR)
– Allows superior control by enabling flow redirection regardless of the routing protocol configured
• Protocol-Independent Multicast (PIM)
– For IP multicast routing within a network that enables the network to receive the multicast feed requested and for switches not participating in the multicast to be pruned-support for PIM sparse mode (PIM-SM), PIM dense mode (PIM-DM), and PIM sparse-dense mode
– Tunneling for interconnecting two multicast-enabled networks across nonmulticast networks
• Private VLAN (PVLAN)
– Provides the ability to restrict communications between hosts at Layer 2 through the use of primary and secondary VLANs
• Full IPv6 routing in hardware
Q. Can I enable static IP routing using the IP Base feature set?
A. Yes, RIP and static routing are supported on the IP Base feature set. Dynamic IP routing protocols (OSPF, BGPv4, EIGRP) are available only on the IP Services feature set.
Q. What Small Form-Factor Pluggable (SFP) modules are supported on Cisco Catalyst 3750-E Series Switches?
A. Cisco Catalyst 3750-E Series Switches support the following SFPs:
• 1000BASE-LX/LH (GLC-LH-SM=)
• 1000BASE-SX (GLC-SX-SM=)
• 1000BASE-ZX (GLC-ZX-SM=)
• 1000BASE-T (GLC-T=)
• 1000BASE-BX 1490nm (GLC-BX-D=) (12.2(25)SEB and later)
• 1000BASE-BX 1310nm (GLC-BX-U=) (12.2(25)SEB and later)
• CWDM (supported after Cisco IOS® Software Release 12.1(14) EA)
• 100Base FX (Cisco IOS Software Release 12.2(20)SE and later)
Q. What X2 modules are supported on Cisco Catalyst 3750-E Series Switches?
A. Cisco Catalyst 3750-E Series Switches support the following X2 modules:
Stacking with StackWise Plus
This section explains the workings of Cisco StackWise Plus technology. In addition, it compares and contrasts StackWise
® and StackWise Plus. Note that the Cisco Catalyst 3750 switches run StackWise, while the Cisco Catalyst 3750-E switches run StackWise Plus and, stacked with a Cisco Catalyst 3750, can also perform StackWise. In this document, the term "StackWise Plus switch" is referring to a Cisco Catalyst 3750-E.
Q. What is Cisco StackWise?
A. Cisco StackWise is a technology that provides an innovative method for collectively using and extending the resources of a stack of Cisco Catalyst 3750 and Cisco Catalyst 3750-E switches. To the rest of the network, the stack operates as a single switch. Cisco StackWise technology is optimized for Gigabit Ethernet deployment, bringing customers new levels of performance through the high-speed interconnect, resiliency through advanced failover mechanisms, and ease of use through automated configuration and a single management interface.
Q. What is StackWise Plus?
A. Cisco StackWise Plus technology is built on the highly successful StackWise technology. StackWise Plus provides an enhanced forwarding mechanism, provides a local switching capability, and adds destination stripping of unicast packets (unlike StackWise, which uses source stripping for all packets). StackWise Plus is optimized for 10 Gigabit Ethernet deployments. Cisco StackWise Plus technology can support up to 468 Gigabit Ethernet ports in a stack or up to 18 10 Gigabit Ethernet ports in a stack.
Q. What is the maximum number of Cisco Catalyst 3750-E Series Switches that can make up one stack?
A. Up to nine Cisco Catalyst 3750-E units can be stacked together.
Q. Which switch features are centralized and which features are distributed with Cisco StackWise?
A. Centralized features are those that are controlled by the master node. Distributed features are shared by the master node and the other member nodes. (See Table 1.)
Table 1. Centralized or Distributed Features in Cisco Catalyst 3750-E Series Switches
Layer 2 Features
802.1D Spanning Tree Protocol, PVST, PVST+
Distributed for all ports, except AgPorts
Spanning Tree Protocol Enhancements (CSUF, BPDU Guard, Root Guard, and so on)
QoS-Egress scheduling using Shaped Round Robin (SRR)
IGMP snooping, MVR, IGMP filtering
IGMPv1, v2, v3
Multicast routing protocols-PIM (Sparse, dense and sparse-dense modes), DVMRP (tunneling)
Q. With StackWise Plus, can the entire stack be managed with a single IP address?
A. Yes, the entire stack is managed through a single IP address.
Q. With CLI, can the entire stack be managed from one switch?
A. With a unified management interface, you can with one command load a single image to all compatible switches on the stack, regardless of which switch it is physically or logically connected to. All CLI commands are directed to the master switch node that controls the configuration management.
Q. Can I run Cisco Catalyst 3750 switches with Cisco Catalyst 3750-E switches in the same stack?
A. Yes, the two series are compatible. When the Cisco Catalyst 3750-E Series detects a non-E-Series Cisco Catalyst 3750, it will negotiate down from StackWise Plus mode to StackWise mode. Thus, the entire stack will now run in the original StackWise mode.
Q. Is local switching supported on the Cisco Catalyst 3750-E?
A. Yes, local switching is only performed on the Cisco Catalyst 3750-E Series. Even if there is a mixed hardware stack of E-Series and non-E-Series switches, E-Series switches can still locally switch.
Q. Does StackWise Plus provide a redundant stack ring architecture?
A. Yes, this architecture provides redundancy using the dual ring arrangement. Stacking ASICs monitor the rings and supervise stack operation, configuration, autoupgrade, and autohealing in case of failures.
Q. What is stack mismatch?
A. A stack mismatch is a condition where stack members do not join the stack because of differences between the joining members and the current stack master. There are three types of stack mismatches: version mismatch, SDM mismatch, and feature mismatch.
• Version mismatch - StackWise Plus requires switch members of the stack to have similar Cisco IOS® Software image types or feature set licenses. That is, if the master runs the IP Services feature set, then all members are expected to have the same type of Cisco IOS Software feature set, although the release level can be different. If this condition is not met, then the stack will go into a version mismatch mode.
• SDM mismatch - This mismatch occurs when a new switch is inserted into the ring and it has been configured with a different or incompatible SDM template.
• Feature mismatch - Occurs when a new member attempts to join a running stack that has an interdependent feature configured that cannot be supported on the new switch member joining he stack.
Q. What is an interdependent feature?
A. An interdependent feature is a feature with a scope extending over multiple switches in the stack: that is, a feature that must be supported on all the switches of the stack. Examples: VLAN configuration details, PBR, VRF, and jumbo frames support.
Q. What is an independent feature?
A. An independent feature is a feature with a scope limited to a single switch in the stack. Such a feature is not dependent on the port-ASIC version. Example: PoE and related features.
Q. Can I clear the feature mismatch conflicts by reloading the stack?
A. Not really. Reloading the stack would result in configuration changes that allow every member of the stack to join. That means that the stack would have a new modified configuration, a configuration compatible with all stack members.
Q. Can I provision a new switch in a StackWise Plus stack?
A. Yes, you can provision a new switch, though you must know in advance if the features running on the stack are compatible with the new switch to be provisioned, in addition to other criteria such as model and Cisco IOS Software image type or feature set.
Q. Provisioning a new switch sometimes fails. Why?
A. There are a few reasons why provisioning fails: the switch ID does not match with the ID provisioned, the switch model does not match with the model provisioned, or the stack is running a feature that cannot be supported on the provisioned switch.
Q. What are the notable differences/features between the Cisco Catalyst 3750-E and the Cisco Catalyst 3750?
A. The differences are as follows:
• Cisco Catalyst 3750-E provides a true line-rate (nonblocking) Gigabit Ethernet to the desktop solution with two line-rate 10 Gigabit Ethernet uplinks.
• The Cisco Catalyst 3750-E is a stackable switch, and it is backward compatible and stacks with the existing Cisco Catalyst 3750 family switches.
• The Cisco Catalyst 3750-E has a backplane switching ASIC, which also makes forwarding decisions, to help the switch perform wire-rate local switching.
• The Cisco Catalyst 3750-E supports dynamic a pluggable module that converts a 10 Gigabit Ethernet slot into a slot that can fit 2 Gigabit Ethernet ports. This allows for easy migration for customers moving from Gigabit Ethernet uplinks to 10 Gigabit Ethernet uplinks.
• The Cisco Catalyst 3750-E supports hot-swappable power supplies.
• The Cisco Catalyst 3750-E supports jumbo frame routing and increases the frame size to 9216 bytes.
• The Cisco Catalyst 3750-E supports uncompressed IPv6 address tables. This allows the software to program the full IPv6 address in the hardware. In addition, equal cost routing for IPv6 uses the uncompressed IPv6 address.
• The Cisco Catalyst 3750-E supports destination stripping of unicast packets.
Q. How many 10 Gigabit Ethernet ports are supported?
A. Two line-rate 10 Gigabit Ethernet ports are supported per Cisco Catalyst 3750-E.
Q. Is jumbo frame routing supported on the Cisco Catalyst 3750-E?
A. Yes, jumbo frame routing is supported.
Q. What types of packets are not hardware-forwarded?
A. The Cisco Catalyst 3750-E switches will completely hardware-forward only IPv4 packets with no options set in Ethernet II encapsulation. This includes bridging, routing, security, and QoS lookups. Packets that do not conform to all three criteria will be forwarded using a combination of hardware or software forwarding. IPv6 is also supported in hardware.
Q. What is onboard failure logging (OBFL)?
A. OBFL provides a mechanism for applications to store critical data in nonvolatile memory in hardware, which can be used by the TAC for troubleshooting and fixing hardware issues. The OBFL data will be recorded on the flash as a separate file system.
Q. What are the management port and its functionality?
A. An out-of-band Ethernet management port is supported in addition to the console port. This port works like a normal Ethernet port except that there is not a data forwarding path. One can connect to the master node, regardless of which switch in the stack one connects to. The stack can be managed by using CLI, SNMP, and HTTP. The CLI can be accessed by connecting directly to the management port or through Telnet. The stack master switch responds to the Telnet, SNMP, and HTTP requests.
Q. In a stack of Cisco Catalyst 3750-E switches, how many management ports can be enabled?
A. Only one can be enabled at a time.
Q. How many SPAN/RSPAN sessions does the Cisco Catalyst 3750-E support?
A. Two sessions are supported.
Q. How many destination ports are supported per SPAN session?
A. Up to 64 are supported.
StackWise Plus and Ring Performance
The following section discusses performance values for the Cisco Catalyst 3750-E and stacks composed of Cisco Catalyst 3750-Es. It also contains figures to help explain the answers.
Q. In terms of throughput, what is the main difference between StackWise Plus and the original StackWise?
A. In terms of throughput, there are two main differences between StackWise and StackWise Plus.
Refer to Figure 1, where a packet being sent from Switch 1 to Switch 2. StackWise uses source stripping, and StackWise Plus uses destination stripping. Source stripping means that when a packet is sent on the ring, it is passed to the destination, which copies the packet and then lets it pass all the way around the ring. After the packet has traveled all the way around the ring and returns to the source, it is stripped off the ring. This means bandwidth is used up all the way around the ring, even if the packet is destined for a directly attached neighbor. Destination stripping means that when the packet reaches its destination, it is removed from the ring and continues no further. This leaves the rest of the ring bandwidth free to be used. This ability to free up bandwidth is sometimes referred to as spatial reuse. Note: Even in StackWise Plus broadcast and multicast packets must use source stripping, because the packet might have multiple targets.
Figure 1. Destination Stripping and Source Stripping
StackWise Plus can locally switch. StackWise cannot. Furthermore, in StackWise, since there is no local switching and since there is source stripping, even locally destined packets must traverse the entire stack ring. (See Figure 2.)
Figure 2. Local Switching
Q. Is StackWise Plus compatible with regular StackWise?
A. Yes. StackWise Plus is compatible with StackWise. When there is a stack containing StackWise and StackWise Plus, the two nodes will autonegotiate and run in StackWise mode.
Q. When I stack Cisco Catalyst 3750 and Cisco Catalyst 3750-E switches in the same stack, do I lose local switching capability?
A. No, but overall stack switch forwarding capacity is reduced to 32 Gbps, because the ring negotiates down to StackWise mode.
Q. What is the maximum throughput of a stack composed of StackWise Plus
(Cisco Catalyst 3750-E) and StackWise (Cisco Catalyst 3750) switches?
A. The maximum ring side throughput in this configuration would be 32 Gbps because the nodes will autonegotiate to StackWise mode, which has a throughput that is up to 32 Gbps bidirectionally. Note that the StackWise Plus devices can still perform local switching. This would then add to the overall throughput of the stack. Thus the overall throughput of a StackWise Plus and StackWise stack is dependent on the number and type of Cisco Catalyst 3750-E devices.
Q. Will StackWise and StackWise Plus switches run the same software?
A. Yes, they can run the same software version.
Q. Will autoupgrade work with a mixed StackWise Plus and StackWise stack?
A. Yes, as long as they have the same feature license level. Otherwise, they must be upgraded individually.
Q. Will autoconfiguration work with a mixed StackWise Plus and StackWise stack?
A. Yes, as long as they have the same feature level. Otherwise, some features might be lost.
Q. Will automatic unit replacement work with a mixed StackWise Plus and StackWise stack?
A. Yes, as long as the node replacing the broken node is of the same type and has the same software license level.
The following section explains how the QoS mechanisms work for the Cisco Catalyst 3750-E. This includes marking, queuing, and ACLs.
Q. Explain the Queuing in the Cisco Catalyst 3750-E.
A. In Figure 3, the Cisco Catalyst 3750-E has two ingress queues and four egress queues. Each of the two sets can be configured for one queue to be a priority queue that gets completely drained before the other weighted queue(s) gets serviced. Or, each set can be configured to have all weighted queues.
Figure 3. Cisco Catalyst 3750-E Ingress and Egress Queues
The Cisco Catalyst 3750-E employs SRR. SRR is scheduling service for specifying the rate at which packets are dequeued. With SRR there are two modes, shaped and shared. Shaped mode is only available on the egress queues. Shaped egress queues reserve a set of port bandwidth and then send evenly spaced packets as per the reservation. Shared egress queues are also guaranteed a configured share of bandwidth, but do not reserve the bandwidth. That is, in shared mode, if a higher priority queue is empty, instead of the servicer waiting for that reserved bandwidth to expire, the lower priority queue can take the unused bandwidth. Neither shaped SRR or shared SRR is better than the other. Shared SRR is used to get the maximum efficiency out of a queuing system, because unused time slots can be reused by queues with excess traffic. This is not possible in a standard Weighted Round Robin (WRR). Shaped SRR is used to shape a queue or set a hard limit on how much bandwidth a queue can use. When you use shaped SRR, you can shape queues within a port's overall shaped rate.
In addition to queue shaping, the Cisco Catalyst 3750-E can rate limit, physical ports from 1 percent to 99 percent of line rate. Thus you can shape queues within an overall rate-limited port.
Q. What is the difference between WRR and SRR in shared mode?
A. The preceding question introduces the topic of SRR; refer to it before continuing. See Figure 4.
Figure 4. WRR and SRR
In the examples, Q4 has the highest weight, Q3 lower, and so on. Strict priority queuing is turned off.
SRR differs from typical WRR. With WRR queues are serviced based on the weight. Q1 is serviced for Weight 1 period of time, Q2 is served for Weight 2 period of time, and so forth. The servicing mechanism works by moving from queue to queue and services them for the weighted amount of time. With SRR weights are still followed; however, SRR services Q1, moves to Q2, then Q3 and Q4 in a different way. It does not wait at and service each queue for a weighted amount of time before moving on to the next queue. Instead, SRR makes several rapid passes at the queues; in each pass, each queue might or might not be serviced. For each given pass, the more highly weighted queues are more likely to be serviced than the lower priority queues. Over a given time, the number of packets serviced from each queue is the same for SRR and WRR. However, the ordering is different. With SRR, traffic has a more evenly distributed ordering. With WRR one sees a bunch of packets from Q1 and then a bunch of packets from Q2 and so on. With SRR one sees a weighted interleaving of packets. In Figure 4, for WRR, all packets marked 1 are serviced, then 2, then 3, and so on until 5. In SRR, all A packets are serviced, then B, C, and D. With SRR there will be interleaving (biased by the weights) for smoother traffic flows. SRR is an evolution of WRR that protects against overwhelming buffers with huge bursts of traffic by using a smoother round-robin mechanism.
Q. Does the Cisco Catalyst 3750-E support congestion avoidance?
A. Yes. Weighted tail drop (WTD) can be applied on any or all of the ingress and egress queues. WTD is a congestion-avoidance mechanism for managing the queue lengths and providing drop precedences for different traffic classifications. Configurable thresholds determine when to drop certain types of packets. The thresholds can be based on class-of-service (CoS) or differentiated services code point (DSCP) values As a queue fills up, lower priority packets are dropped first. For example, you can configure WTD to drop CoSs 0 through 5 when the queue is 60 percent full. In addition, multiple thresholds and levels can be set for different CoS and DSCP values, on a per-queue basis.
Q. Does the Cisco Catalyst 3750-E support aggregate policing?
A. The Cisco Catalyst 3750-E supports aggregate policers where several traffic flows can be policed as a group.
Q. How does the Cisco Catalyst 3750-E classify packets?
A. The Cisco Catalyst 3750-E can classify packets based on the following:
• Layer 2 - MAC SA, DA, 802.1p, Ethertype, ingress port number.
• Layer 3 - IP Destination Address, IP Source Address.
• Layer 4 - port number, and IP Type of Service (ToS).
Q. Does the Cisco Catalyst 3750-E support egress traffic shaping?
A. Yes, traffic shaping is supported on a per-queue basis, giving the customer great flexibility, because traffic can be mapped to the egress queues based on a per-ACL, flow, CoS, DSCP, and so on basis.
Q. Does the Cisco Catalyst 3750-E support the ability to set the trust state of a port for QoS?
A. Yes, the Cisco Catalyst can be configured to trust a port's CoS, DSCP, or IP precedence. This can be performed on a per-VLAN basis. This is important, because you need to be able to trust the value of higher priority voice VLAN traffic.
Q. Does the Cisco Catalyst 3750-E's QoS support the ability to mark packets in both the ingress and egress directions?
A. Yes, the Cisco Catalyst 3750-E can mark CoS and DSCP in both the ingress and egress directions.
Q. Does the Cisco Catalyst 3750-E's QoS support the ability to schedule packets on both ingress and egress, as part of a congestion-avoidance mechanism? Describe the implementation.
A. Yes. This is discussed in the section about ingress and egress QoS.
Q. Is the IP services license required for Layer 3 QoS?
A. No, both the IP Base feature set and the IP Service feature set can perform Layer 3 QoS.
Q. Is the IP Services feature set required to allow Layer 3 and Layer 4 lookups for QoS and security?
A. No, both the IP Base feature set and the IP Services feature set allow for Layer 3 and Layer 4 lookups for QoS and security.
Q. How granular can the policing be?
A. The committed information rate (CIR) is 8 KB to 1 GB, and the burst rate is 8 KB to 1 MB.
Q. Describe policing as it relates to VLAN policies.
A. Although a policy map can be applied to the VLAN interface, any policing or rate-limiting action can only be performed on a per-port basis: that is, it is impossible to have the policer configured generally to take account of the sum of traffic from a number of physical ports. Each port needs to have a separate policer governing the traffic coming into that port. Each interface must be specified in a second-level policy map by the class map that matches that interface.
Q. Is per-flow policing supported?
A. Yes, per-flow policing is supported.
Q. Is port rate limiting supported?
A. Yes, port rate limiting is supported from 1 percent to 99 percent of the given port's speed.
Q. Is egress policing supported?
A. Egress policing is not supported. However, different packet flows can be mapped into queues. These queues can then be shaped. This will limit the amount of traffic on those flows, similar to that of egress policing.
Generic Online Diagnostics
This section discusses Cisco Generic Online Diagnostics (GOLD) tools that provide real-time diagnoses for hardware and software issues that might arise on the Cisco Catalyst 3750-E and 3560-E.
Q. What is GOLD?
A. GOLD is a Cisco IOS Software subsystem that was initially developed by and has been adopted by several Cisco platforms. GOLD is an important feature because it allows users to run comprehensive nondisruptive and disruptive tests to be used in diagnosing hardware and software problems.
Q. What tests are included in GOLD?
A. GOLD is a suite of diagnostics tests that address the need for comprehensive troubleshooting tools that can be used by customers or the TAC. The diagnostics are as follows:
• Health monitoring - Periodic running of nondisruptive tests while the system is in operation.
• On demand - Tests run interactively with the administrator
• Scheduled - Tests run at a specific time daily, weekly, or just once. Correct operation is dependent on the time source being configured on the switch, such as by manual user input or NTP.
Q. Do I need to load a special diagnostic image onto the switch to run GOLD?
A. No, GOLD is part of runtime Cisco IOS Software, unlike many competitors' switches.
Q. Do I have to take a switch out of service to run GOLD diagnostics?
A. No, many GOLD diagnostics can be run without taking the switch out of service and without disrupting traffic.
Q. Can GOLD be run on demand and at scheduled intervals?
A. Yes, GOLD diagnostics can be run on demand or scheduled.
Q. Can I run GOLD tests on an entire switch stack?
A. Yes, GOLD allows the administrator to control the tests on all the switch members of the stack through the stack master.
Q. Does the on-demand interactive test include disruptive tests, and can the test be aborted?
A. Yes, on-demand tests include disruptive tests. Those tests will require a confirmation from the user to abort the tests. This includes reloading or splitting the stack.
Q. How many tests can I schedule, and can I run the tests more than once?
A. A user can schedule multiple and unlimited tests. Those tests can be schedule to run once, daily, or periodically.
Q. Are health monitoring tests disruptive to switch operations?
A. No, the health monitoring tests are run in the background and can be disabled/enabled using the CLI.
Q. How often are health monitoring tests run?
A. An interval for each test can be configured. The frequency ranges are 365 days to 15 seconds, and the granularity is as small as 50 milliseconds.
Q. Where are test results, schedules, and health monitoring configurations stored?
A. All information is stored in flash and in the configuration file. That is, schedule and health monitoring configurations are part of the switch configuration.
Q. In case of a stack master reload, do I lose the test results and GOLD configuration?
A. No, All configurations and test results are retained during a master switchover.
Q. Can I configure GOLD for switches already provisioned in the stack?
A. Yes, a user can add a GOLD configuration to provisioned switches in the same manner as any other configuration on provisioned switch members of a stack.
This section discusses the operation and uses for Cisco FlexLinks.
Q. What is FlexLinks?
A. FlexLinks is a feature that provides Layer 2 resiliency, typically run between access and distribution switches. It has faster convergence times over Spanning Tree Protocol/Rapid Spanning Tree Protocol/IEEE 802.1w. FlexLinks is implemented on Cisco Catalyst 3000 Series and Cisco Catalyst 6000 Series switches. FlexLinks provides subsecond convergence in less than 100 ms. That is, there is less than a 100-ms convergence time from the active link's failure detection to the forwarding of traffic on a backup link. FlexLinks is deployed in pairs: that is, two ports. One port is the active port, and the second is a backup port. Those ports can be either an access port, an EtherChannel
® port, or a trunk port.
Q. Does FlexLinks disable Spanning Tree Protocol on the Cisco Catalyst 3750-E?
A. No, FlexLinks only disables Spanning Tree Protocol on the FlexLinks pair. That is, only the uplink ports configured for FlexLinks (active and backup) will have Spanning Tree Protocol disabled. It is recommended that Spanning Tree Protocol not be disabled on all of the remaining ports, to avoid network loops.
Q. Is the backup port blocked just like with Spanning Tree Protocol?
A. Not necessarily. The latest enhancements to FlexLinks allow the backup port to be active for some VLANs. These same VLANs are backed up by the active port, much like Multiple Spanning Tree Protocol. This is called load balancing and allows users to have two active links rather than one active and one backup. While some VLANs use one link as active, other VLANs use that same link as backup.
Q. Is there a load balancing mode in FlexLinks?
A. Yes, there is a VLAN balancing configuration. In a dual homed configuration, some VLANs will use one link as the active link (Link A) and the other as the backup link (Link B), while the others will use Link B as the active link and Link A as the backup. (See Figure 5.)
Figure 5. FlexLinks Load Balancing
Q. Can I make a ring topology with FlexLinks?
A. No, FlexLinks is intended for uplinks as an alternative to Spanning Tree Protocol. A ring topology is not supported.
Q. Can I configure FlexLinks over EtherChannel ports, trunks, or access ports?
A. Yes, FlexLinks can be configured on all port types, EtherChannel ports, trunks, and access ports.
Q. Must active and backup ports be of the same port type?
A. No. Ports pairings can have an EtherChannel port as the active port and an access port as a backup port and do not have to be of the same speed.
Q. After a failover, is preemption supported in case the high-bandwidth primary link comes back online?
A. Yes, preemption can be configured, but is off by default. Preemption can be configured based on a port's bandwidth. Also, delays can be added in case the primary link is flapping to avoid multiple switchovers from active to backup. Also, preemption can be forced; in this case, the delay timer is ignored.
Q. Does FlexLinks have a tuning mechanism that allows users to avoid link flap?
A. Yes, delays can be added in case the primary link is flapping to avoid multiple switchovers from active to backup.
Q. Do I have to enable MAC move updates (MMU) with FlexLinks?
A. No, but MMU is recommended in order to speed up bidirectional convergence. MMU notifies the switches in the distribution layer about MAC table changes. Note: The Cisco Catalyst 6000 product line does not support MMU, but it is on the roadmap.
Q. Can I use FlexLinks pairs across the stack?
A. Yes, FlexLinks pairs can be deployed across different switch members of the same stack for either the active or the backup link. This arrangement increases high availability.
Q. Should I turn off Spanning Tree Protocol when FlexLinks is running?
A. No, Spanning Tree Protocol will only be disabled on the FlexLinks pair by default. Spanning Tree Protocol will be used on other ports and the VLAN of the switch.
The following section explains the security features on the Cisco Catalyst 3750-E.
Q. What are the supported violation modes in the port security feature?
A. The interface can be configured for one of the following violation modes.
• Protect - When the number of secure MAC addresses reaches the limit allowed on the port, packets with unknown source addresses are dropped until a sufficient number of secure MAC addresses is removed or the number of maximum allowable addresses is increased. In this mode, the user will not be notified that a security violation has occurred. Note that Cisco does not recommend enabling the protect mode on a trunk port. The protect mode disables learning when any VLAN reaches its maximum limit, even if the port has not reached its maximum limit.
• Restrict - When the number of secure MAC addresses reaches the limit allowed on the port, packets with unknown source addresses are dropped until the user removes a sufficient number of secure MAC addresses or increases the number of maximum allowable addresses. In this mode, the user is notified that a security violation has occurred. An SNMP trap is sent, a syslog message is logged, and the violation counter increments.
• Shutdown - In this mode, a port security violation causes the interface to immediately become error-disabled and turns off the port LED. It also sends an SNMP trap, logs a syslog message, and increments the violation counter.
Q. What are DHCP snooping and DHCP option 82?
A. DHCP snooping allows the switch to "snoop" the switching traffic for DHCP packets. It acts like a firewall between hosts and the DHCP server. It provides DHCP-specific security features such as:
• Verifying the intercepted DHCP messages from untrusted ports
• Performing per-port DHCP message-rate limiting
• Keeping track of DHCP IP address assignment binding between the DHCP server and clients
• Inserting DHCP option 82 into and removing DHCP option 82 from DHCP messages
DHCP option 82 provides an easy way to locate which port a user is attached to, using the client's IP address. This extension to DHCP enables an edge switch to insert information about itself in the DHCP request packet that is destined to the DHCP server.
Q. What do I need to configure, on upstream routed interfaces, if DHCP option 82 is configured on the access switch?
A. If DHCP option 82 information is being inserted, upstream routed interfaces must be configured with a trust relationship to the downstream DHCP snooping switches that add option 82. This is done with the IP DHCP relay information trusted command, in the VLAN interface configuration toward the downstream switch.
Q. What is the DHCP snooping binding table?
A. The DHCP snooping binding table contains the following:
• DHCP option 82 information
• MAC address
• IP address
• Lease time
• Binding type
• VLAN number
• Interface information that corresponds to the local untrusted interfaces of a switch
However, the table does not contain information regarding hosts interconnected with a trusted interface.
Q. What is the maximum number of DHCP snooping binding table entries?
A. Up to 8000 entries are supported.
Q. How can I keep the bindings intact when the switch reloads?
A. To keep the bindings intact when the switch reloads, use the DHCP snooping database agent. The database agent stores the bindings in a file at a configured location. When reloading, the switch reads the binding file to build the DHCP snooping binding database. The switch keeps the file current by updating it when the database changes.
Q. What is the dynamic ARP inspection (DAI) feature?
A. DAI is used to inspect all ARP requests and replies coming from user-facing ports to help ensure they belong to the ARP owner. The ARP owner is the port that has a DHCP binding matching the IP address contained in the ARP reply. ARP packets from DAI trusted ports are not inspected and are bridged to their respective VLANs. The feature is configured on per-VLAN basis.
Q. What is the IP source guard (IPSG) feature?
A. IP Source Guard dynamically creates an ACL based on the contents of the DHCP snooping binding table. This ACL will enforce traffic to be sourced from the IP address issued at DHCP binding table and prevent any traffic from being forwarded by other spoofed addresses.
Q. Why is DHCP option 82 required to implement IP Source Guard with IP and MAC address verification?
A. IP Source Guard can perform source IP and MAC checking or only source IP address checking. However, IP MAC filtering is achieved by using both port security and DHCP option 82. Enabling port security with switchport port security is required on the interface. In addition, for IP MAC filtering, option 82 is required on the switch and the DHCP server. Option 82 is required since the switch does not perform any MAC address learning for DHCP and ARP packets when IP MAC filtering is configured. This is done to prevent a security hole, since any host can formulate a bogus DHCP and ARP packet. If option 82 is not supported on the DHCP server, IP MAC filtering will still work using static bindings.
Q. Do DAI and DHCP snooping prevent denial-of-service (DoS) attacks?
A. Yes, DAI helps prevent DoS attacks by limiting the number of incoming ARPs per second on an interface. Because this feature performs validation checks in the CPU, the incoming ARPs on every interface with DAI will be rate limited. DAI performance depends on the number of interfaces within a VLAN.
When the rate of incoming ARP packets exceeds the configured limit, the switch places the port in the error-disabled state. The port remains in that state; a human intervention will be required to shut or unshut the interface for normal processing. An "error-disable" recovery can also be configured, so the ports automatically emerge from this state after a specified timeout period.
Q. What are the supported 802.1x enhancements features?
A. The following features are supported:
• 802.1x authentication with VLAN assignment
• 802.1x authentication with per-user ACLs
• 802.1x authentication with guest VLAN
• 802.1x authentication with inaccessible authentication bypass
• 802.1x authentication with voice VLAN ports
• 802.1x authentication with port security
• 802.1x authentication with wake on LAN
• 802.1x authentication with MAC authentication bypass
Q. What is Network Admission Control (NAC)?
A. NAC assesses the state, or posture, of endpoint devices such as desktop computers, laptops, and servers in order to prevent unauthorized or vulnerable hosts from accessing the network. Authentication and posture validation occur when a host requests access to a network. Through Layer 2 or Layer 3 transport, a network access device (NAD) retrieves posture credentials from the host. The amount of network access granted to the host is determined by its identity and/or level of compliance with posture policy rules, which are defined on the access control server (ACS). These posture credentials are typically based on the state of the host operating system and antivirus applications running on the host.
Q. Is 802.1X, per-user ACL, supported in conjunction with NAC?
A. No, it is not supported.
Q. What is MAC authentication bypass (MAB)?
A. MAB is used to authorize an attached host by authorizing it based on its MAC address.
Q. In case of MAB, If a supplicantless PC disconnects from an IP phone, will the switch get notified of this disconnect?
A. No. The phones will send out Extensible Authentication Protocol Over LAN-Logoff (EAPOL-Logoff), but only if 802.1x was on the wire to begin with.
Q. Is Cisco Clean Access supported in Cisco Catalyst 3750-E switches?
A. Yes, Cisco Clean Access is supported.
Q. Are reflexive or dynamic ACLs supported in Cisco Catalyst 3750-E switches?
A. No, neither feature is supported.
Q. Are time-based ACLs supported in Cisco Catalyst 3750-E switches?
A. Yes, time-based ACLs are supported.
Q. What is storm control, and is it supported on the Cisco Catalyst 3750-E switches?
A. Storm control prevents traffic on a LAN from being disrupted by a broadcast, multicast, or unicast storm on one of the physical interfaces. Storm control uses one of these methods to measure traffic activity:
• Bandwidth as a percentage of the total available bandwidth of the port that can be used by the broadcast, multicast, or unicast traffic
• Traffic rate in packets per second at which broadcast, multicast, or unicast packets are received
• Traffic rate in bits per second at which broadcast, multicast, or unicast packets are received
Q. Is the private VLAN feature supported?
A. Yes, private VLANs are supported.
The following section discusses the PoE features in the Cisco Catalyst 3750-E and Cisco Catalyst 3560-E.
Q. Does the Cisco Catalyst 3750-E PoE switch support the IEEE 802.3af standards-based implementation?
A. Yes, the Cisco Catalyst 3750-E PoE switches support both the Cisco prestandard PoE implementation, as well as the IEEE 802.3af PoE implementation.
Q. What method of disconnect does the Cisco Catalyst 3750-E PoE support?
A. The Cisco Catalyst 3750-E PoE switches support AC disconnect detection for both IEEE802.3af standard compliance and prestandard Cisco Powered Devices (PD)
Q. What method of detection does the Cisco Catalyst 3750-E PoE support?
A. The Cisco Catalyst 3750-E PoE switches support both Cisco prestandard PoE and standards-based PoE method of detecting a PD. Both detection methods are active at the same time, and either one can be used to detect a valid PD.
Q. Do the Cisco Catalyst 3750-E PoE switches support power classification?
A. Yes, Cisco Catalyst 3750-E switches can optionally detect the PD power classification signature and budget the appropriate power. This reduces the maximum power that must be budgeted by the switch and provisioned in the wiring closet.
Q. What is the maximum power per port that the Cisco Catalyst 3750-E PoE can supply?
A. The maximum power supplied by the Cisco Catalyst 3750-E PoE is 15.4W per port.
Q. How does power management work on Cisco Catalyst 3750-E PoE switches?
A. The 24-port and 48-port Cisco Catalyst 3750-E switches support a maximum of 15.4W per port of -48VDC power on all ports over standard Category 3 and 5 unshielded twisted-pair (UTP) cable up to 100 meters. The Cisco Catalyst 3750-E PoE switches monitor and track the requests for power and only grant power when it is available. If the connected PD draws more power, which results in exceeding the system power budget that is available on the switch, then power will be denied to that port and the PD will not power up. If power is denied, the switch rechecks the power budget periodically (every 15 seconds), and continues to attempt to grant the request for power. If power is granted, the switch updates the power budget. Additional power management features are described later in this section.
Q. What pair set is used to support DC power in Cisco Catalyst 3750-E PoE switches?
A. The pairs 2 and 3 (pins 1, 2, 3, and 6) of the four pairs in Category 3 and 5 cables are used for both the Ethernet data signals and the DC power at the same time. The PD must accept either polarity of power from either pair set. This allows both crossover and straight cables to be used. Only straight cables should be used with the prestandard Cisco PDs.
Q. What is the PoE default configuration on Cisco Catalyst 3750-E PoE switches?
A. All the 10/100 Fast Ethernet ports are by default configured as "Auto." This means that PD discovery is enabled and PDs are powered up first come, first served. The 10/100 Fast Ethernet ports can also be configured as "never." This means that the PD discovery is disabled on those ports.
Q. How do the Cisco Catalyst 3750-E PoE switches behave if the PD is connected to wall power?
A. If Cisco Catalyst 3750-E is powering a PD, and then if the PD gets connected to an electrical wall outlet, the switch will continue to report that the PD is powered inline. If a PD is being wall powered first, which in this case means a wall plug is connected before an Ethernet cable, then if wall power is disconnected, the PD will reset and discovery begins.
Q. What kind of safety protection does the Cisco Catalyst 3750-E PoE offer if a port gets an overcurrent condition?
A. Each port on the Cisco Catalyst 3750-E has individual overcurrent and short circuit protection designs. Each port is designed for 350 mAmps and will shut off if current exceeds 400 mAmps for more than 75 ms. A low-ohm short circuit will be detected in less than 1 ms and power will be shut off immediately. Each port is designed to recover from an overcurrent or short circuit condition automatically when the fault is removed. Each port is independent, and a fault on one port does not affect other ports.
Q. Is the power consumption CLI command supported on the Cisco Catalyst 3750-E platforms?
A. Yes. By using the power inline consumption wattage configuration command, you can override the default power requirement specified by the IEEE classification and Cisco Discovery Protocol. The difference between what is mandated by the IEEE classification and what is actually needed by the device is reclaimed into the global power budget for use by additional devices. You can then extend the switch power budget and use it more effectively.
Q. What is the bidirectional Cisco Discovery Protocol (PNP Power Negotiation Protocol), and is it supported on Cisco Catalyst 3750-E PoE switches?
A. PNP enables high-power powered devices (a PD that consumes > 7W) to operate in high-power mode on the Cisco Catalyst 3750-E and the Cisco Catalyst 3750 PoE family switches. This protocol is supported on the Cisco Catalyst 3750 and the Cisco Catalyst 3750-E PoE family switches. PNP is supported currently on Cisco 7970G Phones and is being phased into all high-power PDs. When the high power PDs are connected to the Cisco Catalyst 3750-E and 3750 PoE family switches, the PD boots up in low-power mode and requests to move into high-power mode by incrementing the request ID and sending a list of possible power modes. Upon receiving this request the switch will select the highest mode possible from the list of power modes. The decision on which power mode to select is based on hardware limits, current power available in the global power budget, and user configuration. The switch will set the available power Cisco Discovery Protocol field to the chosen value and respond to the PD request. If a PD is denied transition to high-power mode, it will not request again to transition, unless it is unplugged and replugged into the port.
Q. Is auto-MDIX supported on PoE ports?
A. Yes, auto-MDIX is supported on the Fast Ethernet PoE ports and as well as 10/100/1000 ports. Auto-MDIX operates the same for a PoE port as for a non-PoE port. When auto-MDIX is enabled, and a traditional PD is connected to the Cisco Catalyst 3750 or 3750-E PoE switches with crossover cable, the PD is detected and power is granted, followed by an AC disconnect. This behavior happens repeatedly until the cable is changed. Auto-MDIX only works if the port is configured for autospeed and autoduplex.
Q. What are the discovery and disconnect timing restrictions required by IEEE802.3af?
A. The Cisco Catalyst 3750 and 3750-E PoE switches detect the connected PD within 500 ms. After successful detection, the switch turns on the power within 400 ms. At the time of disconnect, power is removed from the port within 500 ms.
Q. How is PoE delivered over Gigabit Ethernet pairs? How is that different than PoE over Fast Ethernet pairs?
A. The PoE feature is -48VDC power provided over standard Category 3 and 5 unshielded twisted-pair cable up to 100 meters on the Fast Ethernet 10/100 and 10/100/1000 Gigabit Ethernet copper port.
Q. How much power is budgeted for a powered device that does not support IEEE power classification?
A. 15.4W is budgeted.
Q. Can I support 15.4W on all 48 ports?
A. Yes, the total PoE power available on the Cisco Catalyst 3750-E with 48 PoE ports would depend on the installed power supply modules in the switch. With a 1150W power supply the 48-port switch can support up to 15.4W of power per port.
Q. Is there PoE on the SFP ports that use the 10/100/1000 SFP?
A. No, PoE is supported only on the copper ports, not on the fiber ports.
Layer 2 Features
The following section explains the Layer 2 features for the Cisco Catalyst 3750-E. They include Layer 2 forwarding, MAC learning, Spanning Tree Protocol, and so on.
Q. How many EtherChannel groups are supported in a Cisco Catalyst 3750-E?
A. Forty Eight groups are supported, and each group can have up to 8 ports with the same speed, duplex mode, native VLAN, VLAN range, trunking status, and type.
Q. How many Spanning Tree Protocol instances are supported on the Cisco Catalyst 3750-E?
A. 128 Spanning-Tree Protocol instances, 1024 VLANS, 63 bridge groups and up to 4000 user-configurable VLAN IDs.
Q. Is Network Address Translation (NAT) supported?
A. No, there are no plans to support NAT.
Q. Is the full private VLAN feature supported?
A. Yes, it is supported in the IP Services feature set. In the IP Base feature set the private VLAN edge (protected port) feature is supported. In addition, the local proxy ARP feature is supported, and thus no external router is required.
Layer 3 Features
The following section covers Layer 3 functionality in the Cisco Catalyst 3750-E
Q. Are the BGP and IS-IS routing protocols supported?
A. BGP is supported. There are no plans to support IS-IS.
Q. Is there a roadmap for support of IPX and AppleTalk routing?
A. No, there are currently no plans to support either IPX or AppleTalk routing. Fallback bridging can be configured to allow bridging of non-IP traffic between VLANs. Fallback bridging is supported in hardware.
Q. How many switched virtual interfaces (SVIs) can be created on the Cisco Catalyst 3750-E switches?
A. Up to1000 SVIs can be created.
Q. Does the Cisco Catalyst 3750-E support GRE tunneling?
A. No. The Cisco Catalyst 3750-E can switch "transient" GRE tunneled traffic in hardware at wire rate, but it cannot act as a GRE tunnel endpoint. Future support of GRE tunneling in software is possible.
Q. Does the Cisco Catalyst 3750-E support WCCP?
A. Yes, the Cisco Catalyst 3750-E supports WCCP.
Q. Is jumbo frame routing supported on the Cisco Catalyst 3750-E?
A. Yes, jumbo frame routing is supported.
IP Version 6 (IPv6)
The following section explains the features supported for IPv6 on the Cisco Catalyst 3750-E and Cisco Catalyst 3560-E platforms.
Q. Is IPv6 routing implemented in the hardware?
A. Yes, IPv6 routing is implemented in the hardware.
Q. Is special licensing needed to run IPv6 routing on the Cisco Catalyst 3750-E?
A. Yes, the IP Services license is required to run IPv6 routing features in hardware.
Q. Is special licensing needed to run IPv6 host features on the Cisco Catalyst 3750-E?
A. No, the IPv6 host features such as Telnet, neighbor discovery, FTP, ping, and so on are included in the IP Base feature set.
Q. Explain the behavior of an IPv6-capable Cisco Catalyst 3750-E switch within the stack.
A. Cisco Catalyst 3750-E switches support IPv6 forwarding across a stack. It uses the centralized model, similar to IPv4 unicast routing. The master switch runs the IPv6 unicast routing protocols and computes routing tables. Using Distributed Cisco Express Forwarding, the master switch downloads routing table to slaves. Slave switches receive these tables and install IPv6 routes into hardware for a hardware forwarding information base (FIB). For IPv6 routing to work across a stack, the master switch must run an IPv6-capable feature set with IPv6 capability. Member switches can run any feature set, but only member (slave) switches that run IPv6 feature set will be able to support IPv6 forwarding in hardware. That is, IPv6 packets entering the stack through those switches will be forwarded in hardware. Packets entering through other switches will go through software forwarding. Software forwarding is slow and can compromise the CPU by dominating it with requests. This is not recommended.
On master switchover, a new master recomputes IPv6 routing tables and distributes to all of its members.
Q. What standard IPv6 services are supported?
A. Complete support is provided for:
• IPv6 protocol: RFC-2460
• IPv6 addressing architecture: RFC-2373
• ICMPv6: RFC-2463
• Neighbor discovery: RFC2461
• IPv6 stateless autoconfiguration: RFC-2462.
• IPv6 duplicate address detection: RFC-2462
• Jumbo packet IPv6 routing
• MTU path discovery for IPv6 unicast: RFC-1981
• MPv6 redirect: RFC-2463 ICMP
• Support for hop-by-hop options header
Q. What routing protocols are supported in IPv6?
A. The following routing protocols are supported:
• Static routes within IPv6
• OSPFv3: RFC2740
Q. What IPv6 applications are supported?
A. The following applications are supported:
• SSH over an IPv6 transport
• DNS resolver for AAAA over IPv4 transport: RFC-1886
• DNS resolver for AAAA over IPv6 transport: RFC1886
• HTTP server access over IPv6 transport
Q. Can I tunnel IPv4 traffic over an IPv6 network?
A. No, the Cisco Catalyst 3750-E doesn't support tunneling, you have to run the IPv4-and-IPv6 TCAM template to switch and route IPv6 traffic.
Q. Is MLD snooping supported?
A. Yes, MLD snooping is supported.
This section discusses the software activation for the Cisco Catalyst 3750-E.
Q. What is software activation, and how does it work?
A. Software activation authorizes and activates the Cisco IOS Software feature set. A special file contained in the switch, called a license file, is examined by Cisco IOS Software when the switch is powered on. Based on the license's type, Cisco IOS Software activates the appropriate feature set. License types can be changed or upgraded to enable a different feature set. Note that a particular license file only functions with the switch for which it was created. A license file cannot be copied to a different switch.
Q. What are the different types of feature set?
A. There are two types of software licenses: IP Base and IP Services.
• IP Base - Enables Layer 2 forwarding, basic IPv6 functionality, and basic Layer 3 routing, including EIGRP stub mode.
• IP Services - Includes IP Base and enables advanced Layer 3and IPv6 routing such as OSPF and Multicast routing.
Q. What is a product activation key? What are the different types?
A. Product activation keys (PAKs) are purchasable items, ordered in the same manner as other Cisco equipment, that are used to obtain license files for feature set on specific classes of switches. (See Table 2.)
Table 2. Cisco Catalyst 3750-E PAKs
IP Services for 3750-E 24 ports, upgrade from IP Base
IP Services for 3750-E 48 ports, upgrade from IP Base
Q. Does software activation affect Cisco IOS Software version upgrades?
A. No, Cisco IOS Software versions can be upgraded without changing the existing feature set license.
Q. With software activation, is there any change to the RMA process?
A. No, there is no change to the RMA process. However, a switch's product ID (PID) and unique device identifier (UDI) identify the software license installed at the time of manufacturing. If this license file is changed to a different type by the customer, the customer should note the new license type in the RMA request. This will help ensure the replacement unit has the appropriate installed license type.
Q. Where is the software license stored on the switch?
A. The license file is stored on a special area of the flash memory in the switch. The license file is not directly viewable within the switch's file system, but the command line interface (CLI) exists to view and manage the license file.
Q. What happens if the software license file gets corrupted? Will the switch still work?
A. The license file is stored in a special area of memory that is not directly accessible, so it is unlikely to become corrupted. In the event of corruption, the switch will continue to function until it is reloaded/rebooted, at which time it will only enable the IP Base feature set. If possible, the license must be reinstalled; otherwise the switch can be returned using the Cisco RMA process.
Q. How is a software license changed or upgraded?
A. A license can be changed or upgraded following a four-step process.
1. Purchase a PAK for the desired type of license.
2. Submit the PAK code and UDI of the switch to the Cisco online license portal.
3. Install the license file returned from the license portal to the switch.
4. Reboot the switch to enable the new feature set.
The Cisco License Manager can be used to facilitate this process over a large number of switches.
Q. Can licenses be used if the switch is purchased from a third party? What is the process?
A. Although the ownership of hardware can be transferred through a third-party transaction, the right to use Cisco IOS Software cannot be transferred. A software relicense must be purchased from Cisco for the desired feature set. Software relicense part numbers typically start with "LL." Note that relicenses do not require a PAK to be used or a license file to be installed. The existing license file on the switch can remain in use. With a valid Cisco.com user account, switch owners can use the "Cisco License portal" to access license information by submitting the switch's device certificate. The certificate can be obtained from using the CLI or an appropriate network management tool.
Q. How are software licenses managed?
A. Several options exist to manage software licenses. The CLI provides the ability to install, view, and remove software licenses. This functionality is also available through SNMP for integration with standards-based network management tools. For a larger number of switches, the Cisco License Manager discovers and manages the licenses for up to 8000 switches. Cisco License Manager can be used in standalone mode or integrated with the CiscoWorks family of management tools.
Q. In a stack of Cisco Catalyst 3750-E switches, must the same type of feature set be used on each switch?
A. StackWise Plus combines powerful failover capabilities with unified software management. By using the same type of feature set on each switch in a stack, failover and software management features work as designed: simply and transparently.
This section discusses the Cisco Redundant Power System (RPS) 2300 as well as the power supplies in the Cisco Catalyst 3750-E and 3560-E.
Q. What is the purpose of the RPS 2300?
A. The Cisco RPS 2300 provides users with uninterrupted network services in the event of an internal power supply failure. The Cisco RPS 2300 is used with fixed configuration Cisco Catalyst switches, including the Cisco Catalyst 3750-E switches, and routers such as the Cisco 2800 Series Integrated Services Routers. The RPS 2300 helps ensure a transparent failover from internal power supply failures for one or two supplies or up to six connected switches or routers. The RPS 2300 automatically senses when a connected device has experienced an internal power supply failure and immediately begins to supply power to the device, providing continuous uptime with no device reboot.
Q. Is the RPS 2300 the same as an uninterruptible power supply (UPS)?
A. No, an RPS protects network devices against internal power supply failures and failure of an AC circuit (for example, circuit breaker tripping). A UPS protects these devices against interruption of utility power. For maximum availability, the RPS should always be used in conjunction with a UPS.
Q. Will the failover mechanism in the RPS 2300 prevent a switch reboot?
A. Yes, the RPS 2300 is designed to help ensure continued operation of the switch or router in the event of a power supply failure.
Q. How many switches can be connected to an RPS 2300?
A. Up to six switches can be connected to the RPS 2300.
Q. How many of the connected switches can be actively backed up with a single
A. The number of switches actively backed up by the RPS 2300 depends on the number and capacity of power supply modules in the RPS and the type to devices they are backing up. (See Table 3.)
Table 3. Number of Switches Actively Backed Up by RPS 2300
RPS 2300 PS Configuration
1 x 750W
2 x 750W
1 x 1150W
2 x 1150W
Catalyst 3750E-48PD switches with 1150W PS
All other supported network devices
Q. Can the RPS 2300 support PoE switches as well as data-only switches?
A. Yes, it supports both. However, the total power available to the switches would depend on the number and capacity of power supply modules in the RPS. Refer to Table 3 for details.
Q. Can the switch and the RPS 2300 be attached to separate power circuits?
A. Yes, the RPS 2300 and the switch can be on separate circuits. As long as at least one circuit is in service and providing power, the attached switch will receive power.
Q. In the event of near-simultaneous failures, on all the switches connected to an RPS 2300, can certain switches be configured to receive higher priority from the RPS?
A. Yes, the Cisco RPS 2300 allows users to configure priorities. Cisco devices connected to the higher priority ports will fail over to the RPS 2300 first.
Q. When a Cisco Catalyst 3750-E or 3560-E switch's power supply fails, is it possible to change the power supply of the switch while it is being backed up by the RPS 2300, without affecting the flow of switched traffic?
A. Yes, it is possible to change the power supply on a Cisco Catalyst 3750-E or 3560-E being powered by the RPS 2300 without causing any switch downtime. The only exception to this is with DC power supplies (C3K-PWR-265WDC). It is recommended the switch using DC power supplies be turned off when changing power supplies, for safety reasons.
Q. When the failed power supply of a Cisco Catalyst 3750-E or 3560-E switch is reinstated, will the switch automatically revert back to its own power supply?
A. Yes, the RPS will detect that the switch's power supply has been reinstated and will hand off the power to the switch's supply.
Q. Does the RPS 2300 offer enhanced management features when connected to Cisco switches?
A. Yes, the RPS 2300 offers enhanced management capabilities when attached to the Cisco Catalyst 3750-E and 3560-E switches.
Q. Can the power supply modules used for the RPS 2300 be reused in other Cisco networking devices?
A. The RPS 2300 power supplies are compatible with the power supplies used in the Cisco Catalyst 3750-E and 3560-E.
Q. What support services are available for the Cisco Catalyst 3750-E Series Switches
A. Cisco and its partners are specialists in Cisco Desktop Switching products and technologies, business analysis, and project management. Cisco services are available through various service programs designed to help accelerate customer success throughout the network lifecycle.
Whether you are migrating your existing Cisco Desktop Switching solution or deploying a new solution, this approach helps align business and technical goals throughout the solution lifecycle. Upgrading from one IOS feature set (IP Base) to another (IP Services) involves the software activation process described in this document. Customers must purchase a feature set-specific SMARTnet contract to ensure service coverage for newly activated Cisco IOS feature sets.
Q. Why should I purchase a Technical Services contract?
A. From common operation inquiries to complex network issues, Cisco SMARTnet
® services provide immediate access to vital information and assistance:
• Rapid problem resolution with full-time global access to the Cisco Technical Assistance Center (TAC)
• Registered access to Cisco.com for powerful online tools and information
• Next-business-day advance hardware replacement (additional replacement options, some as fast as two hours, are also available)
• Ongoing system software updates that enable the network to evolve to changing business needs and increase return on investment (ROI)
• Cisco OS software support to extend the life of Cisco devices with improved security, increased performance, bandwidth management, new protocol support, and greater interoperability
Q. Does the Cisco Catalyst 3750-E Series interoperate with Cisco LocalDirector?
A. Yes, the Cisco Catalyst 3750-E supports per-SVI router MAC addresses.
Q. How does the Cisco Catalyst 3750-E Series prioritize control packets that do not already have priority information in the DSCP or 802.1p field?
A. The hardware does not automatically prioritize control packets such as BPDU and routing updates. VACLs can be used to classify these packets to high priority to help ensure they are not dropped during congestion.
Q. Does the Cisco Catalyst 3750-E support time domain reflectometry (TDR)?
A. Yes. Cisco Catalyst 3750-E switches support TDR on its 10/100/1000 interfaces. TDR is not supported on 10/100 or 1000BASE SFP ports.