Configuring Cisco 877 for redundany with ADSL and DSL

[sameershrestha]

Hi All,

I would like to configure a Cisco 877 M router with two ISP connection. One is an ADSL service and the other is a DSL service (EFM).

Basically what i would like to achieve here is to keep one of the link on standby and quickly failover when the other one is down.

Can any one please help provide me with an info regarding the config and how i will be able to achive this.

Much appreciate your help!

Thank You.

[cadet alain · Accepted solution]

Hi,

1) create ip sla object pinging an external IP

    ip sla 1
        icmp-echo 8.8.8.8
   ip sla schedule 1 start now life forever

2) use PBR or a static host route for the ip sla ping test using primary path

      ip route 8.8.8.8 255.255.255.255 dialer0

3) create a track object tracking the status of the preceding ip sla object

    track 2 rtr 1

4) create a static route for primary path using the track object

    ip route 0.0.0.0 0.0.0.0 dialer0 track 2

5) create a floating static route for the secondary path

      ip route 0.0.0.0 0.0.0.0 dialer1 2

6) create  2 route-maps for dynamic PAT with match on ACL and outgoing interface

     route-map DIAL0
    match ip address 101
    match interface dialer0
   route-map DIAL1
   match ip address 101
   match interface dialer1

Note : ACL 101 will tell which traffic must be natted

7) create 2 NAT overload statements using the route-maps

    ip nat inside source route-map DIAL0 interface dialer0
   ip nat inside source route-map DIAL1 interface dialer1

Regards

Alain

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[sameershrestha]

Hi Alian,

Thank you very much for the post. I have not tested this yet. Looks like all the config should be good.

I was also wondering what would change if the second link is configured as Fa0/0 with IP address instead of dialer interface.

Much appreciate your help!

Regards,
Sam

[cadet alain · Accepted solution]

Hi,

in the route-map you would match interface f0/0 instead of dialer and in your NAT you would use f0/0 instead of dialer

and for the static route you would point it to the next-hop instaed of the outgoing interface and everything else stays the same.

Regards

Alain

Don't forget to rate helpful posts.

[sameershrestha]

Hi,

Thank You very much for your help in this.

Much Appreciated.

Regards,
Sam