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New Member

Multiple external multicast feeds - Advice needed

Hi all,

I am working on a site which uses 2 x 6500's as network core.

-----------------------------------

For historical reasons, there is a mix of configurations which have been applied, not necassarilly all by the in-house team.

Overall, WAN links for external multicast feeds are connected to CISCO routers and then the routers connected to the core(s) in required VLANs.  The multicast for any particular service is maintained by the routers and I understand no vlan interface on the cores has PIM enabled.  Historically, multicast has been restricted to the internal network and not distributed to external sites.

Auto-RP has been enabled on the core(s) due to a requirement of a particular application within one of the VLAN's.  Auto-RP is distributing the following addresses:

224.0.0.0/4; 224.0.0.39/32; 224.0.0.40/32

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Now, I'm connecting a remote office over a 100Mbps leased line which requires the multicast of one of the feeds at the main site.  The multicast addresses to be sourced are in the range 224.0.x.0.

I'd like some advice on how the multicast can be distributed to the remote office without affecting performance or making too many changes to the cores at the main site.

One easy way would be to join the WAN link with the WAN ports in switchport access mode within the VLAN at the main site for the particular multicast feed, but this means all the broadcast traffic is distributed to either end in addition to the pim broadcasts.  There must be a more efficient way.

I could also link the WAN via trunk ports and distribute different VLAN's and associated pim broadcasts as needed, but again unneeded broadcasts would be sent unnecessarily across the link to each site.

I  think the setup (in the file attached) would be CISCO-receommended, but it does mean adding pim to an internal VLAN interface which the main site would prefer not to do.  Considering the info above, please comment on my config attached and let me know your advice / recommendation.

My biggest concern is that by adding pim to the VLAN interface at the main site, it causes 'bad' behaviour with the AUTO-RP - Especially because the AUTO-RP is distributing 224.0.0.0/4.

Thanks,

Mario

1 ACCEPTED SOLUTION

Accepted Solutions
Hall of Fame Super Silver

Re: Multiple external multicast feeds - Advice needed

Hello Mario,

>> Would I be correct in assuming the PIM broadcasts etc. would be  distributed to the remote clients in the same VLAN as if they were at  the main site?

no if ip pim sparse-mode or ip pim sparse-dense-mode is not given under the appropriate SVI interface

ip pim neighbor-filter can be used to enable IP PIM without building PIM neighborships.

if using a L2 port the requirement is that the remote site has to act as L2 only device

So I don't see any advantage in this setup but only disadvantages of carrying useless broadcast traffic over the link

Hope to help

Giuseppe

6 REPLIES
Hall of Fame Super Silver

Re: Multiple external multicast feeds - Advice needed

Hello Mario,

a routed solution is to be preferred with PIM enabled on link to new remote site.

on the core side of link to remote site you can implement appropriate filtering of PIM joins coming from remote site to avoid side effects of the 224.0.0.0/4 block.

you need also to update the ACL used by candidate RP to include range 224.0.x.0

the mroute static routes are not strictly needed until RPF check for the source of Group 224.0.x.0 is passed.

That is remote site has to use the WAN link to reach the source of multicast traffic

one option is ip pim accept-register directly on candidate RP

http://www.cisco.com/en/US/docs/ios/ipmulti/command/reference/imc_04.html#wp1039548

Hope to help

Giuseppe

New Member

Re: Multiple external multicast feeds - Advice needed

Hi Giuseppe,

Thanks for replying.

I spoke with the guys at the main site again and for one reason or another, they are very reluctant to enable pim on the core side for this connection.

So unfortunately, it looks like a trunk or switch port between locations is the only possibility.  I'm tending to put in a trunk port in case additional VLAN access is needed later on.

Would I be correct in assuming the PIM broadcasts etc. would be distributed to the remote clients in the same VLAN as if they were at the main site?

We intend to manage access with Port based ACL's.

Should I be concerned about anything with the above setup?

Mario

Hall of Fame Super Silver

Re: Multiple external multicast feeds - Advice needed

Hello Mario,

>> Would I be correct in assuming the PIM broadcasts etc. would be  distributed to the remote clients in the same VLAN as if they were at  the main site?

no if ip pim sparse-mode or ip pim sparse-dense-mode is not given under the appropriate SVI interface

ip pim neighbor-filter can be used to enable IP PIM without building PIM neighborships.

if using a L2 port the requirement is that the remote site has to act as L2 only device

So I don't see any advantage in this setup but only disadvantages of carrying useless broadcast traffic over the link

Hope to help

Giuseppe

New Member

Re: Multiple external multicast feeds - Advice needed

Thanks again Giuseppe,

That makes sense.

I hope to convince the client to use the L3 interfaces as initially planned.

Cheers,

Mario

Re: Multiple external multicast feeds - Advice needed

Mario

I understand you do not want to make any change to you cores but another option is you could have MSDP peering between your Core devices which use TCP as its transport protocol connections on well known port 639.

Multicast Source Discovery Protocol (MSDP) is a PIM protocol. MSDP interconnects multiple PIM-SM domains which enables PIM-SM to have Rendezvous Point (RP) redundancy and inter-domain multicasting.

How it will work for you is your routers are connected to their local RP (Core router at a site)  and your Core routers have MSDP (Over TCP) peering with each other across sites so each multicast tree has to have its own local RP. All of the RPs than have MSDP peering over. The purpose of this topology is to allow domains to discover multicast sources from other domains. If the multicast sources are of interest to a domain which has receivers, the normal source-tree building mechanism in PIM-SM will be used to deliver multicast data over an inter-domain distribution tree. All of these is done over layer 3 path, no need to have vlans extended

See http://www.cisco.com/en/US/docs/ios/solutions_docs/ip_multicast/Phase_1/mcstmsdp.html

Francsco

New Member

Re: Multiple external multicast feeds - Advice needed

Hi Francisco,

Thanks for this info.  I may use it at another site later on.

For now, it seems the WAN connection will simply be trunked and the multicast video distributed that way - as per my reply to Giuseppe above.

Mario

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