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Unable to use a WAN link if one link fails out of two links

       We are using two WAN links Airtel (MPLS) and TATA (P2P). Default gateway in Switches is 10.7.251.1 (AIrtel link router). So all the traffic flow is thro Airtel router. We routed some traffic to TATA link from there. When the Airtel link is in UP state as per the routing thr data flow is wright. but when the Airtel link goed down the routed traffic after reaching TATA router (10.7.251.18) terminates and we are unable to connect the external network.   

Routing at Airtel router

         We need use this TATA link even when this Airtel link went down. Please help me

ip route 192.168.61.15 255.255.255.255 10.7.251.18

ip route 192.168.61.161 255.255.255.255 10.7.251.18

ip route 192.168.61.163 255.255.255.255 10.7.251.18

When Airtel is UP

untitled.JPG

When Airtel goes down

Af lnk dwn.JPG

Everyone's tags (4)
2 REPLIES

Unable to use a WAN link if one link fails out of two links

Prabhakaran,

If you have configured static routes pointing towards Airtel router, no matter what the switch will always route the traffic to that even if there is failure at WAN.

Consider deploying two static routes (floating as we call) from your switch to each ISP

ip route 0.0.0.0 0.0.0.0 interface to ISP-A 10

ip route 0.0.0.0 0.0.0.0 interface to ISP-B 150

Together with Reliable Static Routing Using Object Tracking solves the problem. Enhanced Object Tracking introduces a generic track object that can track a state of an interface (layer-2 or layer-3 state), presence or metric of an IP route.

Configure ip sla object pinging a next hop address or even a any address reachable via the Primary link

ip sla 10

icmp-echo x.x.x.x source-interface <>

timeout 500

frequency 3

ip sla schedule 10 life forever start-time now

Create a track object monitoring the reachability of the SLA target

track 10 rtr 10 reachability

After configuring the track object, attach it to the primary static default route to ensure that the default route is removed if the SLA object is not reachable

ip route 0.0.0.0 0.0.0.0 interface to ISP-A 10 track 10

The reliable static routes silently appear or disappear from the IP routing table based on the state of the attached track object which will help you route traffic out the TATA link in case the Primary link fails.

Unable to use a WAN link if one link fails out of two links

Also prabha..... If you have two diff routers to connect to the ISP's... you can have the HSRP between the LAN end routers to acheive it.....

Bharthi to LAN rtr A

Tata to LAN rtr B.

If you are running bgp then you need to define a metric for the primary and backup accordingly.

Please rate if the given information helps.

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