Multiple ISPs, multiple Gateways

[kishanbarwaliya]

I'm working with internal network 192.168.7.0/24 and default gateway is 192.168.7.254 (Our main ISP). Now we have another ISP. I want to make our secondary ISP to work only when our Primary ISP is down. Can this be achieved and if yes, how?

-Thanks.

[Zaaf Aba]

Hi

Yes, this is possible using static route with higher AD or  ip sla tracking.

I am guessing that your router currently has an configuration similar to 

ip route 0.0.0.0 0.0.0.0 exit_interface_existing _ISP

or 

ip route 0.0.0.0 0.0.0.0 IP_existing _ISP

you need to add another static router as

ip route 0.0.0.0 0.0.0.0 IP_NEW_ISP 2 where 2 is the higher administrative distance

Above will work if the 1st ISP interface goes down physically or logically

Better way of doing this is to use IP SLA and track 

ROUTER(config)# ip sla 1
ROUTER(config)# icmp-echo PINGABLE_IP_ON_WAN source-interface FastEthernet0/0
ROUTER(config)# timeout 1000
ROUTER(config)# threshold 5
ROUTER(config)# frequency 4
ROUTER(config)# ip sla schedule 1 life forever start-time now

ROUTER(config)#track 1 ip sla 1 reachability

verify your tracking using command show track 

Then modify the static route as below

ip route 0.0.0.0 0.0.0.0 IP_existing _ISP track 1

you need to add another static router as

ip route 0.0.0.0 0.0.0.0 IP_NEW_ISP 2

Please let me know if you need further assistance. Certainly the model of your router and ISP connected interface details would have help in designing the config template.

Also if you find this reply help, please make it helpful or solution.

Regards

Zaaf

[balaji.bandi]

adding to other post here is good document and configuration example for your to picture the deployment.

http://www.firewall.cx/cisco-technical-knowledgebase/cisco-routers/813-cisco-router-ipsla-basic.html