Failover and EIGRP

Unanswered Question
Sep 12th, 2009

I am having issues with getting out 2811s to failover from the main link to the back up link. I have a Main router with 2 sites connected to it. Both sites have a fiber/ethernet connection a T1/serial link. The fiber is the main link and the T1 is the backup. I am running EIGRP and have static entries for both as default just with a higher metric for the T1. I think what may be causing me the problem is that when we upgraded the main site router for more ports we used switch ports(vendor lead me that way) and had to create VLANs to pass the traffic. We have had 2 times now where the fiber went down and it didn't failover. For some reason it is not shutting down the interface even tho the router can't communicate with the other router. Can I make this failover and if so what do I need to do?

I have this problem too.
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Firstly - why are ou using static routes & a dynamic routing protocol?

The reason why this will be failing (assumtion) is at the switch end, you are possible pointing the static routes into the SVI (Layer 3 vlan interface) - remember ONLY 1 port has to be up/up for the vlan to remain up. If you fibre connection interface is in the same vlan as other up/up ports - the vlan will remain up and the static route will be valid.

I suggest you change your topology to enable eigrp to run completly, without static routes, interacting with specific WAN vlans.


svanguilder Sat, 09/12/2009 - 02:47

Static routes...I was told that I needed to enter both routes as a for the router to see it as route to send to. Just that I would need to add a higher metric. The networks that the static routes are in the EIGRP networks. If I remove my static routes how can I assign the preferred path?

And yes the fiber is the VLAN. And I am guessing like you say the port on fiber vendors switch is staying up, so the router is keeping the interface alive. I was hoping that there was something I can enable to have it monitor whether the other router as whether it was reachable.

OK - I do not know your topology 100%, but the advise you have been given is not 100%

1) If you have static routes, they will overide any dynamic route

2) If your static routes point out of an interface that never does down - they are always valid even when the circuit connectivity is not

3) You can - just create a vlan just for the fibre connection, and then assign an SVI to that VLAN with an IP address. The just assign the fiber interface into that vlan. If the physical interface goes down - the vlan goes down static routes become invalid and are removed from the routing tables. If you have redundant links with EIGRP then they will take over.

However you can configure EIGRP to have mutiple paths to the remote end over differenet WAN links, and still define a preferred path. This is route manipulaton - there are various ways of doing this.


svanguilder Sat, 09/12/2009 - 04:29

OK...we are using #3 so if the interface on both sides goes go down ie either shutdown or upplugged on both ends it fails over. I can do this manually, but it is a pain. I can just telnet to the local router and shutdown the ethernet interface and then to the T1 interface on the remote router and shutdown the ethernet interface and it will failover, but then when the connection comes back up it won't come back up automagically, I have to reverse the previous process.

But the issue that I am running into is this solution is vendor supplied and both ends plug into a media converter in our facilitiess that is connected by fiber to switches on their network that seem stays up no matter what. So even if they cut fiber somewhere, the the media converter link stays up and hence the router interface still thinks things are good and no failover. And I think even if one sides goes down the other side stays up and that one won't fail over.

What I need to do is find a way to have router A monitor whether it can talk to the ethernet port on router b and same the other way.

But from what you are saying I can remove my static routes and EIGRP will monitor whether it can pass traffic across the preferred route and failover if it can't?

By the way I do appreciate your input on this.

OK - what you want to do is simple, and I see you have 2 options:-

1) Use EIGRP to run dynamic routing over the links, EIGRP have hello and dead timers. If one end does not recevie a hello in a specified period, it reports the neighbour as dead, and removes the routes. Default timers are 5 seconds hello, 15 seconds dead. I personally tweak these to 1 second hello, dead 3. Auto failover in 3 seconds.

2) Continue to use your static routes, but inconjunction with IP SLA (url below)

No problem, glad to advise.


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