Simple multihoming with route-map and NAT

I'm having tough time trying to set up something that looks like it should be rather easy:

Cisco router with:

- one FastEthernet port connected to LAN

- one Ethernet port connected to DSL (PPPoE)

- one Serial port connected point-to-point

DSL gets it's IP assigned from ISP (dynamic), Serial port has static public IP addresses.

What I'm trying to achieve is to route outgoing mail (SMTP) thru Serial port. All other outgoing traffic should be sent thru DSL, also NAT-ed.

Can anyone provide some sample configuration or advice? What I tried to do looks something like:

===================================================== interface FastEthernet0 ip address _local_private_address_ ip nat inside

interface Serial0.1 point-to-point ip address _public_static_address_ ip nat outside

interface Ethernet0 no ip address pppoe enable

interface Dialer0 ip address negotiated ip nat outside

access-list 102 remark allow NAT from local addresses access-list 102 permit ip _local_network_ any

ip access-list extended alNATtoSerial permit tcp _local_network_ any eq smtp

route-map rmNATtoDSL permit 10 match ip address 102

route-map rmNATtoSerial permit 10 match ip address alNATtoSerial

ip nat inside source route-map rmNATtoDSL interface Dialer0 overload ip nat inside source route-map rmNATtoSerial interface Serial0.1 overload =====================================================

Thanks in advance, Bruno

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Among other problems, the route maps are only applied when a translation which is NOT in the translation table is required (at connection setup). If the link then fails, the bad translation for the failed link will continue in use until you stop using it and it times out. You get lucky and have the translate cleared if the serial line goes down hard, but even if you unplug the ethernet, the translations going through it will remain.

It can also be a challenge detecting when one of your links is down.

A search on ping based routing will get you most of the past messages where this topic has been generally addressed.

Good luck and have fun!

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