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srue
Rising star

ASR OTV Design question - not extending all VLANs between DC's

I've looked over too many design/config guides to count at this point, and my scenario/question is this...There are two data centers connected through a single 10G link, with ASR's on both ends, and some L3 switch behind the ASR on either end.  I have only a few VLANs (of many) that need to be extended through OTV.  In this scenario, does the ASR need to be dual homed to the LAN side on each end - a connection for L2/OTV to the inside, and a L3 to the inside LAN for non-extended VLANs (so 3 connections from the ASR total, if you count the WAN side)?

Every design/config guide I've gone through seems to only address it as if all VLANs were being extended.

 

Thanks in advance...

 

1 ACCEPTED SOLUTION

Accepted Solutions

Your typical routing/switching infrastructure will still continue to take care of that. Just think of it like OTV on a stick. When a VLAN needs to be extended it will L2 to the ASR then OTV. VLAN's that do not need to be extended simply use their SVI to exit the VLAN and route as normal. I attached a diagram that might help. Non-OTV traffic will take the light gray lines and route across the LAN/WAN.

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3 REPLIES 3
Collin Clark
Advisor

You need the L2 backside connection for the vlans that are to be extended. You will also need an L3, front side interface, also known as the join interface. You do not need the L3 non-join interface. That should be handled by the edge device. Hope it helps.

Thanks for the response...

But what about VLANs on the backside that aren't to be extended (I only want to extend a subset of the VLANs on the LAN side)?  

 

I know I don't need another 'join interface', but do I need another LAN side connection for non-extended VLANs?

 

Thanks

Your typical routing/switching infrastructure will still continue to take care of that. Just think of it like OTV on a stick. When a VLAN needs to be extended it will L2 to the ASR then OTV. VLAN's that do not need to be extended simply use their SVI to exit the VLAN and route as normal. I attached a diagram that might help. Non-OTV traffic will take the light gray lines and route across the LAN/WAN.

View solution in original post

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