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IP SLA and BGP

jonesl1
Beginner
Beginner

Hello All,

Needing some assistance with an IP SLA setup that I'm having some issues wrapping my head around.     I have a router that has two connections to a remote site router.    One connection from HQ-Rtr has a serial connection to an MPLS cloud using BGP as it's routing protocol.   The other connection is an Ethernet connection to an ASA (which uses an IPSEC tunnel to the remote router).    Here is what I'd like to do.   I'd like to use the MPLS cloud connection as the primary connection.  Once it fails, I would want the Ethernet connection to the ASA to kick in.   However, I would like it to fall BACK over to the MPLS cloud connection in the event that the Serial connection comes back online.    

 

With that said, I know I'll have to use IP SLA to make this work but I'm running into an issue getting it to fall BACK to the primary route.  I'm not sure why.     I'm basically doing the following:

       track 1 ip sla 1 reachability

       ip sla auto discovery
           ip sla 1
                icmp-echo a.a.a.a source-interface Serial1/0
                request-data-size 32
       ip sla schedule 1 life forever start-time now

 

       ip route 1.1.1.0  255.255.255.0  x.x.x.x track 1  (learned via bgp from cloud, metric 20)

       ip route 1.1.1.0  255.255.255.0  y.y.y.y 25

 

So, to me.....this says as long as I can ping a.a.a.a from source int s1/0, the route for network 1.1.1.0 should go to x.x.x.x.   Then once it fails, it falls over to y.y.y.y.   It requires the 25 cost so that it doesn't take precedence over the x.x.x.x route.    Am I seeing this correctly so far?   Then once x.x.x.x comes back online, it SHOULD fall back over to that one being it has the lower cost route of 20.   Is this right?   

 

Well regardless it's not working quite as expected so someone had mentioned something about setting another IP SLA up with a 'Boolean and' statement.   I'm not 100% sure about this so if anyone can explain this to me and how it would work in the above scenario or why it would be done, then that would help also.   Here is what they suggested:

      track 2 list boolean and
         object 1 not

and to change my routes to look like the following:

       ------Remove route for x.x.x.x all-together-------

       ip route 1.1.1.0  255.255.255.0  y.y.y.y track 2

I'm guessing (and I do mean guessing) this says to monitor track 1 and if track 1 is NOT true (false) then apply the route for y.y.y.y? 

Can someone take a look and help me with the concept, I guess maybe I'm in left field here but I'm struggling a bit on making this work.  

Thanks in advance,

     

30 Replies 30

On the central side, I'm redistributing Statics, which is where I'm introducing the route.

Jon Marshall
VIP Community Legend VIP Community Legend
VIP Community Legend

Okay that makes more sense, I though it was me :-)

So when you shutdown the loopback interface on router A your MPLS central site router doesn't receive the route and so should failover to the ASA ?

So what route is the MPLS router showing for that loopback ie. prefix and mask when it's a BGP route.

And what route are you using on the central site router to point to the ASA, again prefix and mask.

Jon


Not you at all. :)   I'm was just trying to understand the concept and implement into my scenario, hopefully eliminating a lot of the convoluted portions.   However, some of those pieces you needed and I wasn't giving them.   I do apologize.

Routing entry for xx.xxx.1.164/32
  Known via "bgp xxxxx", distance 20, metric 0
  Tag xxxxx, type external

Last update from xx.xxx.253 01:18:48 ago
  Routing Descriptor Blocks:
  * xx.xxx.3.253, from xx.xxx.3.253, 01:18:48 ago
      Route metric is 0, traffic share count is 1
      AS Hops 2
      Route tag xxxxx
      MPLS label: none

 

Central site router looks like this:

ip route xx.xxx.1.164   255.255.255.255   xx.xxx.2.226  200