Track the DHCP Default Route
Cisco has published a series of documents describing how you can connect a SOHO site to two ISPs.
Their configuration also includes a nice trick: the ip dhcp client route track number command is a convenient replacement for a static default route with the track option if one of the upstream interfaces uses DHCP and the router generates the default route based on DHCP replies.
We've run across what seems an odd anomaly. When configuring an interface address as DHCP, the address, mask, and DNS options operate correctly but the route table updates only after the initial zero crossing of the 'next timer fires after' value. Occasionally, this timer starts at values of more than 30 minutes.
Have you seen this situation?
interface FastEthernet0
ip dhcp client route track 101
ip address dhcp client-id FastEthernet0
ip virtual-reassembly
....
interface FastEthernet1
ip dhcp client route track 102
ip address dhcp client-id FastEthernet1
ip virtual-reassembly
....
conf t
int fastethernet 0
ip dhcp client route track 101
...
int fastethernet 1
ip dhcp client route track 102
...