Routing - Multicast - Eigrp

Answered Question
Jul 16th, 2009

Ir order for EIGRP to properly work, do you need to add route statements for the multicast 224 networks? Or when you enable multicasting on all routers, does it automatically add the 224 network to the routing table?

Also say we are using Multicast for other things outside a routing protocol (Music on hold), do we need to add multicast addresses to routing table?

thanks

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Correct Answer by Jon Marshall about 7 years 4 months ago

Victor

Just to add to Istavan's post.

EIGRP uses a reserved multicast address of 224.0.0.10. The reserved range of multicast addressing 224.0.0.1 -> 224.0.0.255 is never forwarded by routers. So packets with these addresses are only flooded within the subnet/vlan.

Even if you enabled multicast routing and IGMP snooping packets from the above reserved range would be still be flooded within the subnet/vlan ie. they are in effect broadcasts.

Jon

Correct Answer by Istvan_Rabai about 7 years 4 months ago

Hi Victor,

EIGRP multicast packets are not forwarded by routers to other networks or other routers, so you don't have to enable multicast routing on your network.

If you have a regular multicast traffic like MOH, you may need to configure multicast routing in your network.

There are many configuration options to configure multicast routing depending on the topology of your network and the requirements to forward multicast traffic.

One of the first choices you can make is sparse mode or dense mode.

Both are used in different environments and can have different pros and cons.

Multicast routing has a separate multicast routing table and the multicast routing protocols generally take care of automatic adding of multicast routes to the multicast routing table.

Although there is a possibility to configure static multicast routes manually, it is used to modify reverse path forwarding check, not to route multicast traffic.

Cheers:

Istvan

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Correct Answer
Istvan_Rabai Thu, 07/16/2009 - 05:28

Hi Victor,

EIGRP multicast packets are not forwarded by routers to other networks or other routers, so you don't have to enable multicast routing on your network.

If you have a regular multicast traffic like MOH, you may need to configure multicast routing in your network.

There are many configuration options to configure multicast routing depending on the topology of your network and the requirements to forward multicast traffic.

One of the first choices you can make is sparse mode or dense mode.

Both are used in different environments and can have different pros and cons.

Multicast routing has a separate multicast routing table and the multicast routing protocols generally take care of automatic adding of multicast routes to the multicast routing table.

Although there is a possibility to configure static multicast routes manually, it is used to modify reverse path forwarding check, not to route multicast traffic.

Cheers:

Istvan

Correct Answer
Jon Marshall Thu, 07/16/2009 - 05:48

Victor

Just to add to Istavan's post.

EIGRP uses a reserved multicast address of 224.0.0.10. The reserved range of multicast addressing 224.0.0.1 -> 224.0.0.255 is never forwarded by routers. So packets with these addresses are only flooded within the subnet/vlan.

Even if you enabled multicast routing and IGMP snooping packets from the above reserved range would be still be flooded within the subnet/vlan ie. they are in effect broadcasts.

Jon

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