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If I have 2 possible outbound paths, 1 primary, 1 secondary, and I obviously need the secondary to come up if the primary fails. The problem I am foreseeing though, if the RF signal fails, the links will stay up because there are RF devices between them.

e.g:

enter image description here

From router2 perspective, the link to router1 stays up/up even if the RF signal fails, and it will never fail over to Link 2... (R1 on left, R2 on right)

is there any way to have router2 track actual connectivity (not just the up/up link) to router 1 and have it fail over if it cannot reach it.

Would a routing protocol easily fix this situation? The bottom link does not yet exist, I want to theory craft this first.

Thanks!

ios 15.2(4)m3

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    There are several ways to do this depending on the router models, IOS versions, and configurations. Please edit your question to include those, and a diagram would be particularly useful, too. – Ron Maupin Jan 12 '16 at 19:55
  • IOS 15.2(4)m3 Config's are simply default routes. The bottom link does not exist yet. I am trying to get ideas on how to best implement it. – Helkas Jan 12 '16 at 20:14
  • Include the addressing plan: if you need reachable public IP addresses on LAN1, or if you only intend to do outbound NAT-ed Internet access. The same global IP addresses are reachable from both Internet links, or you ought to manage two blocks from separate ISPs? – Everton Jan 12 '16 at 20:19
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Based on your question about the routing protocol, I will assume you are not running one, but you are using static routes, probably static default routes.

You could use a routing protocol, but you would need to make the connected default route on Link 2 have a worse AD than the default route received from the routing protocol. A routing protocol will also take some time to fail a neighbor, so it wouldn't be instantaneously.

It may be possible, depending on your router/IOS combination, to add tracking to a static route. See: Reliable Static Routing Backup Using Object Tracking

Some router/IOS combinations can use BFD to detect a down neighbor when the link stays up.

  • Genius! Exactly what I was looking for. Thanks. I believe our routers support IP SLA as well. – Helkas Jan 12 '16 at 21:01

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