887 router - two outbound NAT on dynamic IP's

[darren.g]

Hi.

I've got an 887M router which will be configured with two linke - one ADSL, one 3G - both of which will have (obviously) a separately suppplied IP address from the different ISP's being used. The 3G is a backup - plain and simple - for use only when the DSL service flakes out (which it does often)

Routing is pretty simple - I'll either do soemthing with a bit of PBR, or a simple weighted static, but the NAT has me scratching my head a little.

Can I have two outbound NAT pools (ip nat outside) for each interface which will be used ONLY for traffic going out the interface concerned?

For example, I have one for the primary link

ip nat inside source list 2 interface Dialer1 overload

Can I do the same for the second dialer interface like this

ip nat inside source list 2 interface Dialer2 overload

and have them automatically switch to using the dialer 2 IP for the outbound NAT if the dialer 1 link fails?

I don't think I've ever come across this before, so I'm not sure if it can even be done.

Thanks for any input.

[Dennis Mink · Accepted solution]

darren:

Just go:

interface Dialer 1

Description Primary link ISP1

ip address 78.x.x.x 255.255.255.0

ip nat outside

interface Dialer 2

Description Secondary link ISP2  (3G)

ip address 79.x.x.x. 255.255.255.0

ip nat outside

interface FastEthernet1/1

Description Inside LAN segment

ip address 172.168.60.1 255.255.255.0

ip nat inside

access-list 100 permit ip 172.168.60.0 0.0.0.255 any

access-list 100 permit ip 172.168.60.0 0.0.0.255 any

route-map isp1 permit 10

match ip address 100

match interface Dialer 1

route-map isp2 permit 10

match ip address 100

match interface Dialer 2

ip nat inside source route-map isp1 interface Dialer 1 overload

ip nat inside source route-map isp2 interface Dialer 2 overload

ip route 0.0.0.0 0.0.0.0 79.y.y.y   -----> Primary Default route pointing towards Next hop ip of ISP1

ip route 0.0.0.0 0.0.0.0 78.y.y.y 10  -----> Backup Default route with higher AD (10) pointing towards Next hop ip of ISP2 (3G)

let me know if it works


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