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Webcast-Catalyst9k

OTV with same group HSRP between two sites

Hi, does anybody try OTV with HSRP in the same group between two sites ? (Active/Standby)

DG.jpg

from http://www.cisco.com/en/US/docs/solutions/Enterprise/Data_Center/DCI/whitepaper/DCI_1.html#wp1236403

If I disable igmp snooping on 7k (OTV), solution on diagram should work right ? (Flood on all VLAN port Local and Remote Site)

and if I enable igmp snooping it will not work right ? (No IGMP Report [both HSRP Speaker look like multicast sender])

Thank you.

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OTV with same group HSRP between two sites

Attavit,

If you enable OTV between the two sites, you can then stretch the VLAN from the left side of your diagram to the right side.  If you enable a single HSRP speaker/gateway on the left side, and a single HSRP gateway on the right side, this will work, as OTV will not filter the HSRP messages floating across the OTV overlay (by default). 

But that means you now have systems connected to your right-hand switch all talking back across the OTV overlay to the left switch, which may be a performance hit.  If the OTV overlay suffers a fault, or the OTV edge devices suffer a fault, the systems connected to the right-hand switch will not be able to talk out to the rest of your network.

You're not really taking full advantage of OTV in that regard.

Enabling HSRP active speaker on the right side, independently of the HSRP active speaker on the left side in your diagram, you now have two sites taking full advantage of L3 reachability, as well as systems on that VLAN being able to talk to each other across the OTV overlay.

But you need to restrict the HSRP messages from passing across the OTV Overlay.  OTV provides hooks to allow configuration of HSRP/VRRP/GLBP filtering, which is documented here:

https://supportforums.cisco.com/docs/DOC-17931

Otherwise you end up with the HSRP active gateway bouncing from one side to the other in a non-deterministic manner.

Cheers,

- Rebecca

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