07-15-2009 01:33 AM - edited 03-06-2019 06:46 AM
Hi. I'm setting up IP Multicast for the first time (I'm not experienced with Multicast at all), and I'd like a few pointers in how to set it up in the best way. Attached is a sketch of the network as it is now.
In my lab, I've managed to get it to work: the IOS switches seems to have multicast turned on by default. To get the routers to work, I just entered "ip multicast-routing" globally and "ip pim dense-mode" on the participating interfaces.
What I like to know, is how to set up multicast in my network, so only the clients on 10.1.20.0/24 get the multicast traffic from 10.1.10.37. In other words: as little noise as possible :-)
Solved! Go to Solution.
07-15-2009 04:16 AM
Just to add to Giuseppe's/Joseph's posts.
Because you only have a small network you can use static RP. So assuming you choose the 6500 as the RP
1) on the 6500 and 7200 add this command in global config mode -
ip pim rp-address 10.74.2.5
2) Under each of the interfaces on the 6500 and 4500 add
"ip pim sparse-mode"
3) As already noted enable IGMP snooping on all your L2 switches.
4) Make sure that the TTL of the multicast packets are at least set to 3
Jon
07-15-2009 01:55 AM
Hello Ivar,
test in your lab PIM sparse mode is the mode that provides better control.
>> is how to set up multicast in my network, so only the clients on 10.1.20.0/24 get the multicast traffic from 10.1.10.37. In other words: as little noise as possible :-)
Sparse Mode
Hope to help
Giuseppe
07-15-2009 02:30 AM
When I set all four interfaces to Sparse Mode, nothing happens. Do I need to use RP or something when using Sparse?
07-15-2009 04:01 AM
Hello Ivar,
>> Do I need to use RP or something when using Sparse?
yes indeed sorry I didn't write it on first post and also IGMP snooping on layer2 switches is important (may be more important in a campus environment)
you can check RP with:
conf t
ip pim rp
on L3 switch
to verify:
sh ip pim rp mapping
to check IGMP snooping that should be enabled by default
sh ip igmp snooping
see if it says enabled on clients' vlan
edit:
I've seen the network diagram
you need ip pim rp
Hope to help
Giuseppe
07-15-2009 04:16 AM
Just to add to Giuseppe's/Joseph's posts.
Because you only have a small network you can use static RP. So assuming you choose the 6500 as the RP
1) on the 6500 and 7200 add this command in global config mode -
ip pim rp-address 10.74.2.5
2) Under each of the interfaces on the 6500 and 4500 add
"ip pim sparse-mode"
3) As already noted enable IGMP snooping on all your L2 switches.
4) Make sure that the TTL of the multicast packets are at least set to 3
Jon
07-15-2009 04:44 AM
Just the info I was looking for, thanks :-)
One more question though: How can I make sure that the TTL of the multicast packets are set to at least 3? :)
07-15-2009 04:49 AM
"How can I make sure that the TTL of the multicast packets are set to at least 3? :)"
That's done within the application itself ie. nothing to do with the network setup as such. Chances are you will be fine but some multicast apps set the TTL to 1 which means it won't go across routed interfaces. There should be some way within the app to tell it to increase the TTL if that is the case.
Jon
07-15-2009 05:04 AM
As Jon notes, it should be set by the application, although I recall most hosts default to something like 32, 64 or 128. Whatever; if dense-mode has been working, i.e. TTL has been sufficient, then so it's likely so should sparse-mode. (Reason likely - sparse-mode might introduce [initially/permanently] more hops between source and receiver. [But we're now getting much deeper into multicast then you want, or need at the moment, to know. ;) ])
07-15-2009 02:34 AM
Besides Giuseppe's recommendation for using sparse-mode rather than dense-mode to reduce the needless distribution of multicast-traffic, on your switches, if they support IGMP snooping, you would want to insure it's enabled too, to stop the needless distribution of multicast to ports on a network segment.
BTW, sparse-mode is little more complex to configure than dense-mode since a RP needs to be defined.
Also, if your network is such where multiple routers share a network segment, PIM snooping might be used to supress multicast traffic to router ports that don't need the traffic.
PS:
"Attached is a sketch of the network as it is now."
Appears to be missing.
07-15-2009 03:58 AM
Hmm...weird, I did attach it. But anyway: http://www.argaste.com/files/multicast.png
07-15-2009 06:45 AM
Hi,
There is maybe a another way to do this and that is to use auto-rp. By using this feature you do not need to manually configure a rendevous point for every multicast group, instead the network takes care of it automatically.
To enable this you configure a minimum of 2 routers to announce themselves as candidate rendevous points, and a minimum of 2 routers to act as mapping agents. The mapping agents then choose between the 2 candidate routers and automatically assign a router to a multicast group.
It sounds complicated, but once setup you can just leave it alone and let it do its thing. We have been using this configuration for over 3 years now without issue. We also use IGMP snooping on all access layer switches and PIM snooping on core / distribution devices.
In order to use this you need to configure ip pim sparse-dense-mode on your backbone. This is needed for auto-rp to function.
The BCMSN book used to discuss this configuration, but I do not know if it is still included on the course.
HTH.
07-15-2009 07:33 AM
Hello Chris,
good note
there are only three routers in the picture so using manual RP setting is acceptable here.
Hope to help
Giuseppe
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