Optimizing Traffic Flow with Port Controls, Port Trunking, and Filters

Traffic/Security Filters

Filter Types and Operation

Multicast Filters

This filter type enables the switch to forward or drop multicast traffic to a specific set of destination ports. This helps to preserve bandwidth by reducing multicast traffic on ports where it is unnecessary, and to isolate multicast traffic to enhance security.

You can configure up to 16 static multicast filters (defined by the filter command). However, IGMP-controlled filters will override any static multicast filters having the same multicast address as specified by IGMP. The total of static multicast filters and IGMP multicast filters together can range from 389 to 420, depending on the current max-vlanssetting in the switch.

Table 9-10. Maximum Allowed Number of Multicast Filters

Max-VLANs

Maximum # of Multicast Filters

Setting

(Static and IGMP Combined)

 

 

1 (the minimum)

420

8 (the default)

413

32 or higher

389

 

 

N o t e :

C a u t i o n

IP Multicast Filters. Multicast filters are configured using the Ethernet format for the multicast address. IP multicast addresses occur in the range from 224.0.0.0 through 239.255.255.255 (which corresponds to the Ethernet multicast address range of 01005e-000000 through 01005e-7fffff). Any static Traffic/Security filters configured with a multicast filter type and a multicast address in this range will continue to be in effect unless IGMP learns of a multicast group destination in this range. In this case, IGMP takes over the filtering function for the multicast destination address(es) for as long as the IGMP group is active. If the IGMP group subsequently deactivates, the static filter resumes control over traffic to the multicast address.

If Spanning Tree is enabled, then the Spanning Tree multicast MAC address should not be filtered. (STP will not operate properly if the STP multicast MAC address is filtered.)

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