Anything in the 224.0.0.0/24 subnet is equivalent to a broadcast address in the local subnet and will be punted to the CPU.
http://www.iana.org/assignments/multicast-addresses/multicast-addresses.xml I've seen some software that has used 224.0.0.1 for the multicast destination address and will hose your network. Nothing other than control protocols should use 224.0.0.0-224.0.0.255. The 224.0.1.40 is for Cisco RP discovery and is normal The 239.255.255.250 is SSDP and is a Microsoft Thing and is normal The 239.255.255.253 is SLP and is normal ---- Matthew Huff | 1 Manhattanville Rd Director of Operations | Purchase, NY 10577 OTA Management LLC | Phone: 914-460-4039 aim: matthewbhuff | Fax: 914-460-4139 -----Original Message----- From: cisco-nsp-boun...@puck.nether.net [mailto:cisco-nsp-boun...@puck.nether.net] On Behalf Of Peter Rathlev Sent: Friday, March 25, 2011 6:00 AM To: John Neiberger Cc: cisco-nsp@puck.nether.net Subject: Re: [c-nsp] Sup720, multicast bothers the CPU On Wed, 2011-03-23 at 20:55 +0100, Peter Rathlev wrote: > Thanks. We'll try just adding "ip igmp snooping querier" to the specific > SVI to see if this in itself would be enough. Next up we try "ip pim > sparse-mode" on the SVI and "ip multicast-routing" in global. > > I'll keep the list updated on how it went. :-) We now tried both adding an IGMP Querier and enabling multicast-routing and PIM. None of these things stopped the multicast traffic from hitting the CPU. I'm a little puzzled that we actually saw _some_ sources: xxx#sh ip igmp membership [...] *,239.255.255.253 10.26.46.78 00:02:41 02:46 2A Vl46 *,239.255.255.250 10.26.46.77 00:02:43 02:46 2A Vl46 *,224.0.1.40 10.26.46.254 00:02:43 02:53 2LA Vl46 xxx# Just not from the "interesting" groups. We tried restarting both a receiver and a source to see if anything changed, and we never saw joins or "*,<something>". So a few questions more: 1) Could "offset != 0" somehow mean that the flows cannot be hardware switched at all? Every single packet has offset != 0, i.e. no packet observed with offset == 0. We were looking at both an RP SPAN session and a SPAN session covering the VLAN in question. 2) Could 224.0.0.0/24, which they use for this purpose though that's wrong, somehow be treated specially by a Sup720? Any chance it would help using 239.255.255.0/24 instead? Thanks in advance. -- Peter _______________________________________________ cisco-nsp mailing list cisco-nsp@puck.nether.net https://puck.nether.net/mailman/listinfo/cisco-nsp archive at http://puck.nether.net/pipermail/cisco-nsp/ _______________________________________________ cisco-nsp mailing list cisco-nsp@puck.nether.net https://puck.nether.net/mailman/listinfo/cisco-nsp archive at http://puck.nether.net/pipermail/cisco-nsp/