isp backup for two lan

Unanswered Question
Mar 6th, 2007
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Here's the scenario

- we have 2 ISP

- we have 2 LAN, we need to let one of the lan (192.168.1.X) to go to ISP1

and the other (192.168.2.X) to ISP2

if ISP1 goes down, all lan should go to ISP2

if ISP2 goes down, all lan should go to ISP1

We've used the attached configuration on lab.

We can't reach pcs or router beyond router directly attached to the main router(router where the configuration was applied)

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Amit Singh Tue, 03/06/2007 - 01:21
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  • Cisco Employee,


Use Policy based routing and NAT to configure the same.Set both the ISP's address as next hop in the route map and if 1 router is down, it will route all the traffic via other ISP.


Policy Based Routing:

HTH,Please rate if it does.

-amit singh

harinirina Tue, 03/06/2007 - 02:39
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Hi Amit,

What should be modified on the config i've sent?

We use only one router for connecting 2 lans and 2 ISP.

Nat seems working

ip nat inside source route-map NAT-TEST interface Ethernet0/0 overload

ip nat inside source route-map NAT-TT interface Ethernet1/0 overload

But we have problem on routing using the following config.

route-map NAT-TT permit 1

match ip address 101

set ip next-hop verify-availability ISP_2 1 track 124

set ip next-hop verify-availability ISP_1 2 track 123

harinirina Wed, 03/07/2007 - 03:10
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Routing works now.

Backup works only after launching "clear ip nat translation *".

What's missing or Is there a way to do this automatically?

martianfw Sun, 03/25/2007 - 17:03
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Try setting your NAT translation timeouts. For example, to timeout UDP port 500 after 20 seconds:

ip nat translation port-timeout udp 500 20

harinirina Tue, 03/27/2007 - 06:09
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Hi Martian,

We've used EEM and it's working.

We'll test what you've suggested, it seems simpler.



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