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Webcast-Catalyst9k
New Member

HSRP Multicast Traffic Showing at Workstation

Our topology is a 6509 with MSFC at the BDC and a 4006 in the IDF serving the workstations. CGMP is enabled on the 4006. But I notice that about every second I see multicast traffic for port 1985 at our workstations. Since CGMP is enabled at the edge 4006 - why am I seeing this multicast traffic at all ports of the edge?

1 REPLY
New Member

Re: HSRP Multicast Traffic Showing at Workstation

Hello,

Since HSRP uses port 1985; the question became does CGMP block link local multicast addresses.

Here is a cut and paste from this link:

In general, addresses from 224.0.0.1 to 224.0.0.255 are reserved and used by various protocols (standard or proprietary, like HSRP). Cisco recommends that you not use these for GDA in a multicast network. CGMP and IGMP Snooping do not work with this reserved address range

http://www.cisco.com/warp/public/473/22.html

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