Cisco Gigabit Ethernet Switch Module for HP BladeSystem p-Class Release Notes, Cisco IOS Release 12.2(35)SE and later

383623-007

Limitations and Restrictions

Multicasting

These are the multicasting limitations:

• If the number of multicast routes and Internet Group Management Protocol (IGMP) groups are more

than the maximum number specified by the show sdm prefer global configuration command, the

traffic received on unknown groups is flooded in the received VLAN even though the show ip igmp

snooping multicast-table privileged EXEC command output shows otherwise. The workaround is

to reduce the number of multicast routes and IGMP snooping groups to less than the maximum

supported value. (CSCdy09008)

• IGMP filtering is applied to packets that are forwarded through hardware. It is not applied to packets

that are forwarded through software. Hence, with multicast routing enabled, the first few packets are

sent from a port even when IGMP filtering is set to deny those groups on that port. There is no

workaround. (CSCdy82818)

• If an IG MP report packet has two multicast group records, the switch removes or adds interfaces

depending on the order of the records in the packet:

–

If the ALLOW_NEW_SOURCE record is before the BLOCK_OLD_SOURCE record, the

switch removes the port from the group.

–

If the BLOCK_OLD_SOURCE record is before the ALLOW_NEW_SOURCE record, the

switch adds the port to the group.

There is no workaround. (CSCec20128)

• When IGMP snooping is disabled and you enter the switchport block multicast interface

configuration command, IP multicast traffic is not blocked.

The switchport block multicast interface configuration command is only applicable to non-IP

multicast traffic.

There is no workaround. (CSCee16865)

QoS

These are the quality of service (QoS) limitations:

• Some switch queues are disabled if the buffer size or threshold level is set too low with the mls qos

queue-set output global configuration command. The ratio of buffer size to threshold level should

be greater than 10 to avoid disabling the queue. The workaround is to choose compatible buffer sizes

and threshold levels. (CSCea76893)

• When auto-QoS is enabled on the switch, priority queuing is not enabled. Instead, the switch uses

shaped round robin (SRR) as the queuing mechanism. The auto-QoS feature is designed on each

platform based on the feature set and hardware limitations, and the queuing mechanism supported

on each platform might be different. There is no workaround. (CSCee22591)

SPAN and RSPAN

These are the SPAN and Remote SPAN (RSPAN) limitations.

• An egress SPAN copy of routed unicast traffic might show an incorrect destination MAC address on

both local and remote SPAN sessions. This limitation does not apply to bridged packets. The

workaround for local SPAN is to use the replicate option. For a remote SPAN session, there is no

workaround.

This is a hardware limitation: (CSCdy72835)