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Community Member

ip sla source-interface

I'm looking for some clarification on ip sla and track operation specifically with respect to the outbound interface of the sla icmp-echo target.  If the source-interface is specific in the ip sla configuration, i.e.

ip sla 1

icmp-echo a.b.c.d source-interface gig0/0

ip sla schedule 1 life forever start-time now

track 1 ip sla 1


ip route <next-hop> track 1

Is this configuration sufficient to forward the sla packets outbound on gig0/0 and to the next-hop as configured in the default route, assuming the next-hop is directly connected to gig0/0?  Does configuring the track statement with or without the reachability option have an impact on the outbound interface?


In order to ensure the outbound interface of the icmp-echo target, is a host route configuration required?


Re: ip sla source-interface

If the next-hop is directly connected, your router will see it in the routing table as being directly connected as long as gig0/0 is up.

Directly connected networks will not be influenced by a default route since the default is used only when the router doesn't know where to send traffic.

Sh ip route:

C        a.b.c.x/x is directly connected, Gig0/0

Community Member

ip sla source-interface

I may not have been clear in my description.  The next-hop is our ISP gateway but the icmp-echo target is a host *behind* the ISP which obviously needs to be routed through the next-hop.

ip sla source-interface

Understood, the icmp target is not a directly connected network to the router.

As you have it set, it will take the outbound interface of the default route.

If you have multiple external interfaces on the router that you want to work with, you can look at IP SLA used with policy based routing.

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