Redundant ISP Links

mark.j.hodge · ‎01-08-2008

I have setup an ASA cluster to use Redundant ISP Links as show in the cisco example

http://www.cisco.com/en/US/products/hw/vpndevc/ps2030/products_configuration_example09186a00806e880b.shtml

This works fine for outbound traffic, i.e. web browsing. However I would like to use it for inbound as well, connecting to a SMTP server. As I understand it there cannot be two static mappings to the same IP address, from the two ISP CIDR ranges. If I place a second IP address on the SMTP server to allow two mappings I cannot determine which address will be used as the source IP for outbound traffic. I believe this will screw up the connection.

Any ideas, assitance appreciated.

mark.j.hodge · ‎01-10-2008

Policy-Based NAT seems to be the answer.

http://www.cisco.com/en/US/products/ps6120/products_configuration_example09186a00807d2874.shtml

pengfang · ‎01-20-2008

Hi, you need a service called DNS failover, if your primary link is down, your server will be resolved the secondary IP from the other ISP. Here's an exmple ...

http://www.dnsmadeeasy.com/s0306/prod/dnsfosm.html