Configuring for Multicast in a VLAN-only environment

[JimBlake2010]

I have a network which is based upon a 4507 Core/Dist switch, with 1G fibre to a bunch of radially connected 2960 Access switches. It all works fine and as expected for data and telephony.

I have been tasked with setting up one of the VLANs to support multicast, so a bunch of video streams will be injected at the 4507, and will be delivered to client PCs connected to the 2960 switches.

The 4507 is running with SVIs to some VLANs, but the VLAN that will have the Multicast on it is isolated, with no SVI.I could change this if required

I need to run IGMP snooping, and probably deploy CGMP to take advantage of the Cisco-proprietary functionaity.

Does anyone out there have experience/examples/configs that would provide guidance.

Thanks

Jim

[Giuseppe Larosa]

Hello Jim,

you will need an SVI on the servers vlan in order to be able to do unicast and multicast routing from/to that vlan to the rest of the network.

CGMP is quite obsolete and IGMP snooping should be enough for your needs.

You can use ip pim sparse-dense mode on the C4500 SVIs with a static RP that uses a loopback interface

int loop4

desc for multicast

ip address 10.10.10.1 255.255.2255

ip multicast-routing

ip pim rp 10.10.10.10.1

on each SVI including that of the servers

int Vlan X

ip pim sparse-dense mode

By enabling PIM on the SVIs you enable the IGMP on them and in particular the switch will send out IGMP queries.

The last ones are required to make IGMP snooping working on the C2960 ( I suppose they are L2 switches).

IGMP snooping should be on by default on the C2960 switches.

PIM is also needed to perform multicast routing between Vlans.

see

http://www.cisco.com/en/US/docs/switches/lan/catalyst4500/12.2/54sg/configuration/guide/mcastmls.html

Hope to help

Giuseppe

[JimBlake2010]

Hi Giuseppe,

So if I configure "ip pim rp

" to set the address of the rendezvous point on the 4507, does it have to be a loopback, or can it be the SVI of the VLAN carrying the multicast (if I was to create an SVI)?

Also,so long as the switch has routing running (which it has, to allow inter-VLAN traffic for the VLANs with SVIs), is there any restriction on addresses I can use for the Loopback (assuming I don't use an SVI address).

Finally, do I understand you correctly when you say that each 2960 will only require

int Vlan X

ip pim sparse-dense mode

Thanks for your help and answers

Jim

[Giuseppe Larosa]

Hello Jim,

best practice is to use a loopback address as it is up until the node is operational.

You can use an IP address for the loopback taken from your address plan, it is enough that is not in use.

If multiple devices perform inter-vlan routing you would need to configure on all of them the multicast part (all the commands listed in the first post)

Also if multiple routing devices exist you need to advertise the RP address in unicast routing as some PIM messages are sent to the RP address and the ip pim rp command is needed in all multicast routing devices

IF you mean the SVIs you use for management of the C2960 devices, they don't need the command if there is a management subnet/Vlan.

You need to run PIM on all SVIs associated to Vlans where potential receivers or sources of the multicast streams are connected to.

If multiple routing devices exist in the network PIM has to be configured also on inter devices links.

Hope to help

Giuseppe

[Network Admin]

Hello Giuseppe Larosa  ,  am facing similar issues. Could you please give your comments on below link please

https://supportforums.cisco.com/discussion/12684776/multicast-network-configuration-paging-server-informacast

[Joseph W. Doherty]

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Posting

If all your multicast is limited to one VLAN, you shouldn't need to enable multicast routing.  If you're going to do IGMP snooping, you'll need an IGMP querier on the VLAN.  This can be accomplished by using an IP PIM ... command on the VLAN interface.

[JimBlake2010]

Giuseppe, Joseph,

Thanks for both your inputs, they were both useful and extended my understanding of the subject. I haven't yet deployed the config, but if I experience "issues" whe I do, I'll be back. I haven't marked either of your answers as "Correct Answer" because they both added to my knowledge, so to place one over the other seemed inappropriate

Many Thanks

Jim

[Tolulope Osho]

Hi Jim,

I am in your in the same scenario at the moment with no knowledge of multicast at all. I have gone through this post and gained some knowledge from it, however, I would like to know how you finally got your multicast configuration working in your environment.

Regards,

Tolu

[Jim Blake]

Hi Tolu,

I can't add much to the information above, unfortunately.

I did as was suggested by the guys in the respioses, and it all worked real good, but whether that was because of my work, or in spite of it I can't be sure, because the actual amount of multicast that actually ended up going through the network was minimal, despite customer assurances early on on the project that there would be a great deal of it and we had to make appropriate arrangements to support it...

Sorry to be slow in responding, I have been away from my email.

Best Regards

Jim

[Steven.D.Holloway]

Since the VLAN is isolated and has no L3 running or any need for it, you don't need PIM. IGMP will handle the requests to the server.

Remember L2 to is a broadcast boundary so multicast will send all over the place once it's requested by one requester. 

IGMP Snooping should be enabled on all the switches were MC receivers will be connected.

If in the future, you want other networks to be able to see the MC, then PIM and L3 interface on the vlan is needed.

Sparse mode is the recommend feature for PIM

Then there are many different way to learn RPs like AutoRP, Static RP, BSR

[Giuseppe Larosa]

Hello Steven,

multicast can be deployed in a single Vlan without enabling PIM on an SVI.

However, to make IGMP snooping to work a single IGMP snooping querier for the Vlan needs to be configured (multiple are not supported there is no election of the IGMP snooping querier) in a switch otherwise user multicast traffic will not be forwarded as IGMP snooping works on listening to IGMP reports from hosts to build a L2 optimized list of outgoing ports in Vlan for each multicast group.

The IGMP snooping querier sends out IGMP queries allowing all switches to populate their IGMP snooping forwarding tables as I have explained above.

Hope to help

Giuseppe

[uthayaman elangovan]

Do we need to configure RP ? in case if there is only one L3 switch with SVI and multicast need to be enabled in multiple vlans terminating on this switch with leaf switches just acting as L2.