Hi, I need to configure a switched network, based of some catalyst 3750 (ios12.2(40)) in an extended star topology with a basic multicast PIM configuration in sparse-dense mode. I've read something about but I've never do it. Does anybody have experience setting up multicast using a Catalyst Layer3 switch? Thanks in advance. Regards Andrea
i have run this, but only sparse only mode, on Cat 3560s (which are 3750s without the stack connections)
note that sparse / dense is a cisco enhancement over PIM v2 (as is AutoRP), and if you want to interwork with other equipment i suggest you use sparse mode only.
the way my system is set is with 2 BSRs, and multiple RPs.
1 peculiarity of the 3560 / 3750 is you need to set the SDM prefer command correctly (AFAIR we use "sdm prefer routing" to handle the routing table we need).Even then you only have TCAM for 1k multicast hardware entries - since every active flow can use 2 or more hardware entries this might limit what you do.
If you are in a campus setup then you could play around with the rate threshold and make the switches run on the RP and (*, g) entries, but it may hit the RP performance.
exceeding h/w tcam entries will silently fail over to software forwarding, but performance drops like a stone (saw this with unicast and the manuals claim the same for multicast)....
just turn on multicast globally, and on each interface.
make sure you are running a good stable unicast protocol, as PIM uses this to do address checks. We use OSPF, again for interworking.
life gets a bit more complicated if you add L3 equal cost multipath - so avoid it if you can.
there are some limitations in the rel notes (last code i saw was 12.2.40SE - you need enhanced to do PIM) - we had to upgrade to support PIM & VRFs on the same box.
finally - monitoring tools are not fantastic, and multicast can generate lots of complications for debugging.
Thanks Stephen! so I've just another one doubt. The multicast routing is between Vlans or I need to configure some ports in "no switchport" mode and with an ip address to allow that? Thank you so much. Regards. Andrea
you can mix and match routed interfaces with "no switchport" and multicast routing on VLAN interfaces - both seem to work well.
1 complication we have had is that there are other manufacturers kit on this network. Cisco have a multicast to 224.0.1.40 (AFAIR) set up as soon as you use PIM - this is part of the autoRP scheme, and i havent found a way to turn it off.we get issues with this since we have a resilient topology, and the autoRP m/cast gets to the other kit, then gets pushed back. On some of the Cisco boxes we then get "invalid RP join" errors filling the log.
you should be able to filter this using the multicast boundary feature to stop it causing problems
other than that it has been relatively simple - most of our effort has gone into QoS, q handling (as the Cat 3560 3750s are wierd) and OSPF tuning.
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