high availability issue

dear all,
I m having a branch office connected to HO with serial line connected to cisco router 2811 at both the end, now branch office has got their internet from another isp located at their place who has provided a ADSL router, i want to configure the branch office router so that the if any time their internet goes down it should fall over to the headoffice for internet connectivity
pls help me to solve this issue

thanks in advance

regards,
mangesh

Hello Mangesh, so what are you trying to achieve is automatically switch your internet connection to second line as soon as the first goes down? If so then set up a failover for your branch office. Often network administrators setup a failover to avoid any kind of problems related to internet connection.