Release Notes for Cisco Catalyst Blade Switch 3120 for HP, Cisco IOS Release 12.2(50)SE and Later

OL-18270-03

Limitations and Restrictions

• When you configure the IGMP snooping throttle limit by using the ip igmp max-groups number

interface configuration on a port-channel interface, the groups learned on the port-channel might

exceed the configured throttle limit number when all of these conditions are true:

–

The port-channel is configured with member ports across different switches in the stack.

–

One of the member switches reloads.

–

The member switch that is reloading has a high rate of IP IGMP joins arriving on the

port-channel member port.

The workaround is to disable the IGMP snooping throttle limit by using the no ip igmp max-groups

number interface configuration command and then to reconfigure the same limit again.

(CSCse39909)

QoS

These are the quality of service (QoS) limitations:

• When QoS is enabled and the egress port receives pause frames at the line rate, the port cannot send

packets.

There is no workaround. (CSCeh18677)

• Egress shaped round robin (SRR) sharing weights do not work properly with system jumbo MTU

frames.

There is no workaround. (CSCsc63334)

• In a hierarchical policy map, if the VLAN-level policy map is attached to a VLAN interface and the

name of the interface-level policy map is the same as that for another VLAN-level policy map, the

switch rejects the configuration, and the VLAN-level policy map is removed from the interface.

The workaround is to use a different name for the interface-level policy map. (CSCsd84001)

• If the ingress queue has low buffer settings and the switch sends multiple data streams of system

jumbo MTU frames at the same time at the line rate, the frames are dropped at the ingress.

There is no workaround. (CSCsd72001)

• When you use the srr-queue bandwidth limit interface configuration command to limit port

bandwidth, packets that are less than 256 bytes can cause inaccurate port bandwidth readings. The

accuracy is improved when the packet size is greater than 512 bytes. There is no workaround.

(CSCsg79627)

• If QoS is enabled on a switch and the switch has a high volume of incoming packets with a maximum

transmission unit (MTU) size greater than 1512 bytes, the switch might reload.

Use one of these workarounds:

–

Use the default buffer size.

–

Use the mls qos queue-set output qset-id buffers allocation1 ... allocation4 global

configuration command to allocate the buffer size. The buffer space for each queue must be at

least 10 percent. (CSCsx69718)