until now, a customer had his 2 main sites connected via an MPLS cloud, who belongs and is managed by their ISP.
A number of other smaller remote sites are also meshed through this cloud.
Recently, the customer had the opportunity to have the 2 main sites connected through a direct dual fiber link (provided by another ISP).
No L3 routing here, just a straight L1 direct connection.
See attached network diagram.
Here's what we would like to achieve:
1)Use the new fiber link as an L2 trunk between the 2 sites.
2)Use the former L3 MPLS path as a backup link, if the fiber etherchannel goes down.
Step 1 is no problem.
Step 2 doesn't work, because even with the etherchannel going down, either 3750's still see the SVI interface corresponding to the remote site as "up".
Since this SVI stays up, it's considered by the switch as a directly connected connected route, so the default external route will not be used.
In other words, we are trying somehow to make the state of the SVI dependent of the state of the etherchannel.
For example, as soon as we administratively shutdown the other sites's corresponding SVI, then the default route is used to reach the other site.
I know that we could do L3 routing instead of L2 trunking, and then it would be much simpler to make the backup path work.
But for several reasons like e.g. disaster recovery, customer wants each sites's vlans propagated to the other one.
Does somebody have a brilliant idea on how to make the backup route work?
Thanks in advance.