Data-MDT switchover in mVPN

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Sep 12th, 2009
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Hi All,

I tried the following simple topology for mVPN-


CE1 is connected to the source and CE2 has the receiver.

PE1 & PE3 VRF configuration-

ip vrf CUST1

rd 1:1

route-target both 1:1

bgp next-hop Loopback 0

mdt default

mdt data threshold 1 list 100


access-list 100 permit ip any any


I could send the multicast traffic from one end to another using the Default-MDT. PIM adjacency is formed over the MTI Tunnel 0.

The issue is- no matter how much multicast traffic is sent across (multicast traffic here is large ping packets), PE3 does not switchover to Data-MDT.

Please share your thoughts.


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Laurent Aubert Sun, 09/13/2009 - 02:53
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Hi Amit,

You don't need the ACL in your case and mdt-data cmd is only required on the PE connected to the source but it can't explain why it's not working.

This is the PIM debug you should have on PE connected to the source:

*Sep 13 10:36:01.683: PIM(1): MDT threshold exceeded for (,

*Sep 13 10:36:01.683: PIM(1): MDT join sent for (, MDT: Tunnel0

you could try with a threshold of 5 and see if it change something.

If your source is a router sending ping, please set the timeout to 0



amit.bhagat Sun, 09/13/2009 - 04:09
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Hi Laurent,

The "debug ip pim" command should show Data-join TLVs from the PE router when the traffic for (S,G) entry exceeds the set threshold. But I didn't see any such messages.

Just wondering, did you try this in ur lab? Which routers and IOS did you use? I used 2691 with 12.4(25a) IOS. According to Cisco feature navigator, it supports mVPN.



Laurent Aubert Sun, 09/13/2009 - 04:19
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Yes, I tested it with 12.2(33)SRC for 7600 and 12.2(33)SXH for 6500.


ulatif Thu, 09/17/2009 - 16:29
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Could you paste the output of following from your configuration on PE1 and PE3:

"show run | i pim"

"show ip pim mdt bgp"



amit.bhagat Thu, 09/17/2009 - 16:42
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Hi Usman,

show ip pim mdt bgp output is as follows-

PE1# show ip pim mdt bgp

Peer (Route Distinguisher + IPv4) Next Hop

MDT group


Here's another output- It clearly states Default-MDT group is created.

PE1#show ip pim mdt

* implies group is the MDT default group

MDT Group Interface Source VRF

* Tunnel0 Loopback0 CUST1

I dont have the configs at this stage,only had this output handy.

I still need to try Laurent's tip of setting the timeout to 0 since I am send ping packets from a router.

Will update this post once I implement that.

shivlu jain Thu, 09/17/2009 - 22:18
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Hi Amit

The IOS you are using is SRC series and in the outputs you are getting extended community of 2:X:X.

Please let us know have you enabled the ipv4 mdt under bgp or not.

address-family ipv4 mdt

neighbor send-community both

neighbor activate



shivlu jain

amit.bhagat Fri, 09/18/2009 - 06:08
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Hi Shivlu,

I have used this IOS on 2691 router-


Also, I did not enable ipv4 mdt. Most books do not have it enabled, however they could be using older IOS then.

I might have to try enabling ipv4 mdt.



amit.bhagat Mon, 11/16/2009 - 15:20
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Hi All,

Just like to provide an update that this issue was resolved when I switched over to 7200 series routers. I was able to switchover to the Data-MDT as soon as the threshold was reached.

Thank you all.



ulatif Mon, 11/16/2009 - 21:28
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I once had a similar issue in my network where a CPP (control plane policing) policy was dropping the data-MDT joins.

Not saying this is the reason in your case but you might wanna check on these lines:

i.e. whether or not the data MDT join is being generated and makes it through the network while using the 7600/6500


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