HSRP Multicast Traffic Showing at Workstation

[mmedwid]

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?

[HECTOR RIVERA]

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