Default gateway based on interface IP?
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Posted by Rodre on September 8, 2008, 8:03 pm
Please log in for more thread options Hello, Pardon me for any indiscretions, this is my first time posting to this group. I have a Cisco 1720 router with IOS12.3(26) . It's Outside interface has a Primary IP from one carrier, and a Secondary IP from another carrier. I have it filtering and NAT-ing SMTP traffic for our email server which sits in RFC 1918 address space behind it. I have it's primary IP address published in our DNS as the primary MX record. I would like to publish it's secondary IP in our DNS as the backup MX record. The problem is that ISP 'A' won't route packets with the IP address from ISP 'B' (secondary IP) and visa versa. I am guessing that they both have egress filtering turned on and are silently dropping packets that are not part of their address space. My question is: How can I have packets destined for the Primary IP be routed back through ISP 'A's default gateway, and have packets destined for the Secondary IP be routed back through ISP 'B's default gateway? Is this possible? If so what would the NAT rules look like as well? Thanks in advance. ~Rodre | |||||||||||||
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Posted by Thrill5 on September 8, 2008, 9:26 pm
Please log in for more thread options Search Cisco's web site for "route-map". This will allow you to route packets based on the source address of the packet instead of the destination. | |||||||||||||
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Posted by Rodre on September 9, 2008, 7:49 pm
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> Search Cisco's web site for "route-map". This will allow you to route
> packets based on the source address of the packet instead of the > destination. > Hello, Thanks for your reply. I tried this with no success. Can someone provide a short example? Thanks. ~Rodre | |||||||||||||
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Posted by Thrill5 on September 9, 2008, 10:18 pm
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If you go to http://www.cisco.com and type "route-map" into the search field, their are no less than 4 different results on the first result page that return examples of using route-maps. >> Search Cisco's web site for "route-map". This will allow you to route
>> packets based on the source address of the packet instead of the >> destination. >> >
> Hello, > > Thanks for your reply. I tried this with no success. Can someone > provide a short example? Thanks. > > ~Rodre > > | |||||||||||||
>
> Pardon me for any indiscretions, this is my first time posting to this
> group. I have a Cisco 1720 router with IOS12.3(26) . It's Outside
> interface has a Primary IP from one carrier, and a Secondary IP from
> another carrier. I have it filtering and NAT-ing SMTP traffic for our
> email server which sits in RFC 1918 address space behind it. I have
> it's primary IP address published in our DNS as the primary MX record.
> I would like to publish it's secondary IP in our DNS as the backup MX
> record. The problem is that ISP 'A' won't route packets with the IP
> address from ISP 'B' (secondary IP) and visa versa. I am guessing that
> they both have egress filtering turned on and are silently dropping
> packets that are not part of their address space. My question is:
>
> How can I have packets destined for the Primary IP be routed back
> through ISP 'A's default gateway, and have packets destined for the
> Secondary IP be routed back through ISP 'B's default gateway? Is this
> possible? If so what would the NAT rules look like as well?
>
> Thanks in advance.
>
> ~Rodre