Hello Arjun,
the usual setup for your scenario is the following:
you use two routers: R1, R2
ISP link1 is connected to R1
ISP link2 is connected to R2
R1 and R2 share one or more client Vlans and advertise them on EIGRP to the provider on both links.
to get R1 and R2 to share subnets on the internal side you connect R1 Fastethernet (or GE) to a LAN switch and you do the same for R2.
the two LAN links if necessary will carry multiple Vlans (L2 trunks on the switch side).
on the router side the main lan interface has no ip address and Vlan subinterfaces are used
int f0/0
no ip address
int f0/0.10
enc dot1q 10
ip address 10.10.10.2 255.255.255.0
standby 10 ip 10.10.10.1
standby 10 priority 105
standby 10 preempt
standby 10 track interface "WAN side here"
each client Vlan needs at least one HSRP group and you need to use different HSRP group numbers (10 in the example above)
the routers and the HSRP group use 3 addresses: one for each subinterface and one for the VIP
when you configure R2 you just skip the line
standby XX priority 105
this makes R1 the active router for outbound in normal conditions, if the R1's wan link fails all clients will send traffic to R2 that becomes the active router.
if one router fails the other is still able to receive and send traffic.
In some scenarios you can connect the two routers to two different switches in order to achieve fault tolerance to single switch failure.
In this latter case a trunk link between the two switches is needed too. The trunk has to carry all the client Vlans.
Hope to help
Giuseppe
