HP Cisco Catalyst Blade Switch 3020 Cisco Gigabit Ethernet Switch Module for H - Page 9
IP, IP Telephony, Multicasting, QoS, show sdm prefer, show ip igmp, snooping multicast-table
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Limitations and Restrictions IP IP Telephony Multicasting QoS When the rate of received DHCP requests exceeds 2,000 packets per minute for a long time, the response time might be slow when you are using the console. The workaround is to use rate limiting on DHCP traffic to prevent a denial of service attack from occurring. (CSCeb59166) After you change the access VLAN on a port that has 802.1x enabled, the IP Phone address is removed. Because learning is restricted on 802.1x capable ports, it takes approximately 30 seconds before the address is relearned. No workaround is necessary. (CSCea85312) • 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) • 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) Cisco Gigabit Ethernet Switch Module for HP BladeSystem p-Class Release Notes, Cisco IOS Release 12.2(44)SE and Later 464831-005 9