ASM Multicast

[Ab26]

I have some questions about multicasting that I haven't been able to find answers for. We have a full functional multicast setup using PIM sparse-mode with ASM and a static RP, and MSDP peering.

Everything is working well, but I just need clarification on a few commands to understand if they are necessary and their use.

1. Is it necessary to enable multicast routing on the main routing table if I am only using multicast on specific VRFs?

2. Does the "show ip mroute" command display output only when the router is connected to a multicast source or receiver? I.e, if there is no multicast traffic passing through the router, will the output of this command be almost empty?

3. What is the purpose of the commands in bold font, and are they needed for ASM?
vrf definition Multicast_VRF
address-family ipv4
mdt default 235.5.0.0 => is this needed for ASM? and why?
mdt data 235.5.1.0 0.0.0.255 threshold 100 => is this needed for ASM? and why?

4. If MDT is needed, what commands can be used to display which MDT is/are being used?

5. How many PIM neighbors can an ASR-1001x router have?

6. Is the "ip pim ssm default" command required for an ASM setup, and what does it do?

7. Is there an equivalent command in multicast for the unicast command "maximum routes 10000 80 reinstall 90"?

Thank you!

[Harold Ritter]

Hi @Ab26 ,

You need to deploy multicast in the VRF for the customer and also for the global routing table in the core.

> When I issue the "show ip mroute" command, I don’t see any of these mdt. I only see the multicast group   > configured by our team, which is 239.10.10.X.

Have you configured the BGP address family ipv4 mdt?

> Is there a limit on the number of PIM neighbors a Cisco router can have?

There is certainly a limit, but no hard limit that I know of.

> When can I expect to see output from the "show ip mroute" command on routers with multicast sources or > receivers? Will there be output if no multicast sources or receivers are connected to the router?

In the default multicast routing table, you should at least see the multicast address for the default MDT.

In the VRF multicast routing table, you should only see the multicast addresses if there are senders and/or receivers.

Regards, 

[Ab26]

Thanks @Harold Ritter for your reply!

Our set up is like this:

MSDP Route-reflectors => Core => distrubtion routers => Access routers
Core is in the MPLS cloud with no VRFs and no multicast routing, only PIM in all MPLS interfaces (global routing table)
=> so PIM tunnels are created between distrubtion routers
MSDP Route-reflectors have BGP with MDT with the the distrubtion routers
MSDP Route-reflectors and distrubtion routers are MSDP peers
MSDP Route-reflectors and distrubtion routers are in MPLS cloud
MSDP Route-reflectors, distrubtion routers and Access routers have multicast routing enabled for the VRF

There is certainly a limit, but no hard limit that I know of. =>
Is there a way to know that for sure? I looked at Cisco device specification (Data sheets) but nothing mentioned there about any limit for multicast for ASR1001.
I found some info for ASR920
A maximum of 20 multicast VRFs are supported.
A maximum of 255 OIFs are supported.

And for Nexus 9000
Maximum number of PIM Neighbors 1,000
Maximum number of PIM Neighbors per VRF 64
Maximum number of L3Out physical interfaces with PIM enabled 32

In the default multicast routing table, you should at least see the multicast address for the default MDT.
=> no unfortunately, I see groups with 239.10.10.X. but not with MDT

[paul driver]

Hello
You mention Route Reflectors/ASM which suggest this is an iMBGP Mcast pim spare-mode design
Can you elaborate on your topology, maybe share a diagram showing the Mcast source/receivers and Rp's?,

As for MSDP, you do not mention how the peering is being applied, are you using the same peer addressing as the iMBGP or different.

Do you actually obtain an established MSDP peering and if so do you see successful  sa-ache entries?

[Ab26]

Thanks Paul!

It's correct as you wrote. Unfortunately I don't have a diagram on hand at the moment. But, we are using PIM sparse-mode, with Any Source Multicast (ASM) and static RP. The same IP address of RP is configured on multiple distribution router. Each distribution is considered a Multicast domain. Each domain can have Multicast sources and receivers. Multicast is allowed between the domains that's why we are using MSDP. The MSDP peering is fully functional with SA running between the peers (interdomains). 

My confusion is only about the need of MDT and its use on ASM. I think MDT is only used in SSM, but not sure
Second, question was in some places the output is almost empty when I run the (show IP mroute). Does a multicast source or receiver need to be connected to a router for this show command to display output?
Lastly, about the limitation for router ASR-1001x

[Harold Ritter]

Hi @Ab26 ,

Which mVPN profile are you deploying?

 You should have multicast routing configured in the core as well. This would include configuring an RP if you are configuring ASM. RP would obviously not be required if you configure SSM for the default and data MDT.

Regards,

[Ab26]

Thanks @Harold Ritter  for your reply!

We are using Profile 0 Default MDT - GRE - PIM C-mcast Signaling. As for the core, i meant the MPLS cloud. We don't configure VRFs nor multicast routing. We have only PIM enabled on all involved interfaces.
We are using ASM and static RP.
Do I understand from your sentence "SSM for the default and data MDT" is that default and data MDT are only used for SSM?
If so, does this mean that in our case, where we are using ASM, there is no need for the default and data MDT?

So under the vrf definition we can remove mdt default and data

vrf definition Multicast_VRF
address-family ipv4
mdt default 235.5.0.0 => has no effect?
mdt data 235.5.1.0 0.0.0.255 threshold 100 => has no effect?

I'm confused between MDT and multicast group

[Harold Ritter]

Hi @Ab26 ,

> We don't configure VRFs nor multicast routing.

Do you mean that you do not have multicast routing for the global routing table? You need to have multicast routing on the core routers as well. You also need to configure the RP for the core routers.

> Do I understand from your sentence "SSM for the default and data MDT" is that default and data MDT are only used for    > SSM?

Sorry for the confusion. I see that you are using ASM for default and data MDT. I was only suggesting that SSM could be used as well. 

> So under the vrf definition we can remove mdt default and data

No, this is required.

Regards,