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IP SLA statement and Routing

John.Barbour
Level 1
Level 1

I have cisco IR829 Cellular router at one of my locations. What I would like to set up is the following

 

Primary Route is to our Data Center over fiber connection from the MDF.

Backup route is to the IR 829 into or cellular network. 

 

I have a statement inplace but I am not sure on the routing statements.

 

ip sla 829

icmp-echo 10.255.30.1 source-interface Gig1/1/1Routing, Routing Protocols

frequency 600 

timeout 100000

ip sla schedule 829 life forever start-time now

 

track 829 ip sla829 reachability

delay down 10 up 30

 

I would like to keep the route to my data center as eigrp and the secondary route would be static. would it look something like this

 

ip route 0.0.0.0 0.0.0.0 10.30.252.1 200 track 829 

2 Replies 2

mlund
Level 7
Level 7

Hi

You actually don't need the sla and tracking for this to work.

If you specify your static route as this,

ip route 0.0.0.0 0.0.0.0 10.30.252.1 200

Meaning that as long as the eigrp is propagated the default-route, the static route is not used. But when eigrp don't advertise the default-route anymore, your static route is inserted in the routing table automaticly. And when eigrp starts to advertise the route again, it will be inserted in the routing table and the static will be removed.

This is because the AD (administrative distance) is 90 for eigrp, which is lower than 200 that is specified in the static entry.

If you don't specify the 200 in the static route, it will use default value, which is 1, and then the static will always be the one used.

/Mikael

JimWicks
Level 1
Level 1

Why do you want to track the state of the ethernet route using IPSLA ? If I uderstand your ask correctly, it would be far simpler to just use a floating static-route pointing to your cellular interface, with a high enough metric that your EIGRP learned routes are always a preferred while their primary GigE link is up.  So get rid of IPSLA (your EIGRP neighbour updates should keep those routes alive) and your floating static would be something like

 

ip route 0.0.0.0 0.0.0.0 cellular0 200   <-- change the number of the cellular interface to match your device

 

If the IR829 is a different device to this one that you were planning to nail this IPSLA config onto, the same principal applies but the static route just points at the next-hop IP of the IR829 instead.   You don't really need an IPSLA probe on that backup default-route either, because it will only be used if your primary EIGRP path has gone down. If the IR829 is not working at failover time it makes no difference if you detect it or not using the IPSLA, your traffic is still going into the bin because both primary(EIGRP) + secondary(IR829) paths are dead.

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