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Cisco Routing with 2 ISP connection

Dear experts, please refer to my network diagram. I have 2 internet link from 2 different ISP. 1 is main and 1 is backup. I don’t really need WAN load balancing but I would want my mail traffic to come in from either link all the time through primary and secondary MX records. NAT is configured in both the ASA. I can have all my outgoing traffic going out through a single link no problem.  

I’m trying to add in the 1902 router. In my router, I have a statement ip route 0.0.0.0 0.0.0.0 192.168.120.1. This will force all outgoing traffic out via the 1st link. If the 1st link is down I must logon to the router and change the gateway to the other link 192.168.120.2 (Singnet). Can I have more than 1 default gateway so that if I link is down it will route to the other link?

If I only configure 1 default gateway in the router, traffic only comes in from outside to inside through NAT from the active link. That means if my default route points to the ISP A, mail traffic comes in via ISP A and not B. How can I achieve mail to come in from either link all the time without adjusting the default gateway in the router?
network-diagram.pdf
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totallypatrick
Asked:
totallypatrick
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1 Solution
 
Cheever000Commented:
You are looking at IP SLA to do that you can track an object for instance 8.8.8.8 via a specific direction you should static the route to that IP over one of the paths.  For instance ip route 8.8.8.8 255.255.255.255 192.168.120.1

ip sla 10
icmp-echo 8.8.8.8
frequency 30
exit
ip sla schedule 10 life forever start-time now

track 10 rtr 10 reachability

ip route 0.0.0.0 0.0.0.0 192.168.120.1 track 10
ip route 0.0.0.0 0.0.0.0 192.168.120.2 10

http://www.cisco.com/c/en/us/td/docs/ios-xml/ios/ipsla/configuration/15-mt/sla-15-mt-book/sla_icmp_echo.html
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totallypatrickAuthor Commented:
Deer Cheever, many thanks for your reply. Can I track both internet lines?


ip route 0.0.0.0 0.0.0.0 192.168.120.1 track 10
ip route 0.0.0.0 0.0.0.0 192.168.120.2 10 track 10
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Cheever000Commented:
you don't need too track both and if you use the same track number it will remove both of the routes when it is down.  
ip route 0.0.0.0 0.0.0.0 192.168.120.1 track 10  -- This will be the active route as its AD is 1 for static, when track 10 is unreachable it will remove the route from the tracking table
When that occurs, the route below is entered in to the routing table with an AD of 10.  When the other route works again the best route with AD 1 will be re-entered in to the route table.
ip route 0.0.0.0 0.0.0.0 192.168.120.2 10
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totallypatrickAuthor Commented:
thanks Cheever, you're spot on!
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totallypatrickAuthor Commented:
Works well. Thanks!
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