Dual ADSL Connections in one Cisco router

Recently a POS customer wanted to install another ADSL connection at one of their main sites. They wanted this second connection in order to segment some internet connected services off their old connection and onto the new ADSL connection, as these services where saturating the old connection on uploads. Quality of service (QOS) was discussed, but was rejected on the basis that these services really needed the majority of the upload speed available in order to function correctly. Given the requirements listed by the Customer we drafted some solutions with various levels of redundancy and price tags. As our they wanted to keep the solution cost low and were not concerned by redundancy they chose the cheapest option, which was to purchase another ADSL Card and utilise it in their current Router.

The Configuration to allow this single router, two ADSL cards was based on Cisco’s implementation of “policy based routing”.

The ADSL cards where configured as normal, the first was configured as “dialer interface 0” and the second was configured as “dialer interface 1”. For this example Dialer 0 has the subnet 192.168.10.0/24 routed to it by the ISP and dialer 1 has subnet 192.168.11.0/24 routed.

The route-maps for policy based routing were configured as follows:

Route-map PBR permit 10
Match ip address 110
Set interface Dialer0
Route-map PBR permit 20
Match ip address 111
Set interface Dialer1
The ACL’s 110 and 115 are show below:
Access-list 110 deny ip 192.168.10.0 0.0.0.255 192.168.11.0 0.0.0.255
Access-list 110 permit ip 192.168.10.0 0.0.0.255 any
Access-list 111 deny ip 192.168.11.0 0.0.0.255 192.168.10.0 0.0.0.255
Access-list 111 permit ip 192.168.11.0 0.0.0.255 any
The access-lists where configured to allow traffic to flow between the two subnets without having to traverse either ADSL connection.