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Traffic Auto Switch Over ??

Hi All,

    We have 2 internet links with different service providers.Everything is working fine.

Default Static route on L3 is pointing to F/W 1 (to pass Traffic thro ISP1)

Now the problem is If ISP1 link went down or Tunnel went down, Manually we need to remove static route

pointing to F/W 1 & add static route pointing to 2nd F/W.(to pass traffic thro ISP2).

Can i implement configuration in L3 switch with IP SLA in such a way that Auto switch over Happens when ISP1 internet link goes down.(without Administrator )

Can i have configuration please

Pls find the attached Diagram for your reference.

Regards,

Srinadh.

1 REPLY

Traffic Auto Switch Over ??

Hello Srinadh,

Yes, that's one of the options you have. IP SLA will track the route based on the defined parameters. If your primary link fails, the tracked object fails & IP SLA will automagically withdraw the tracked route from the routing table.

One thing to check, make sure your platform supports IP SLA at first. Below is the config which may defer based on your platform.

ip sla 1
icmp-echo 4.2.2.2 source-ip

frequency 30
ip sla schedule 1 life forever start-time now
ip sla enable reaction-alerts

!

track 1 ip sla 1 reachability

!

ip route 0.0.0.0 255.255.255.0 1.1.1.1 track 1

ip route 0.0.0.0 255.255.255.0 2.2.2.2 100

ip route 4.2.2.2 255.255.255.255 1.1.1.1

Notice that i am sending pings to 4.2.2.2 (a global DNS server) because it rarely goes down. So what happens now is, if your primary link goes down, IP SLA fails reaching 4.2.2.2 & it withdraws the tracked route from the routing table (i.e

ip route 0.0.0.0 255.255.255.0 1.1.1.1 track 1). It now adds back the another one with the higher metric into the routing table (i.e ip route 0.0.0.0 255.255.255.0 2.2.2.2 100) .

Make sure you have a static route to 4.2.2.2 always pointing to the primary ISP because if primary comes back online IP SLA will re-instate this path again into the routing table (kind of pre-emption).

Hope this helps.

Thanks

Vivek

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