Hi, I need help on how to achieve ISP level failover for LAN based outbound and DMZ inbound traffic.
Scenario (attached diagram)
LAN -> Firewal1 (in HA) -> WAN Routers (1&2) (in HA using HSRP) -> ISP-01 (Using two different Last miles)
LAN -> Firewal2 (in HA) -> WAN Routers (3&4) (in HA using HSRP) -> ISP-02 (Using two different Last miles)
Incase one last mile fails for any ISP, the second last mile takes over smoothly. However, in case there's outage in ISP itself, there's complete outage for outbound as well as inbound (to DMZ) traffic.
Is there a tested method for failover between ISP implemented to figure out the pro's and con's and if it can be implemented so that the complete traffic from WAN Routers 1 & 2 can be shifted to WAN routers 3 &4 and vice-versa. This would primarily help save outage in all inbound traffic to DMZ as the outbound can still be shifted from the LAN source.
Did some research and found BGP prepend working for some n/w's, looking for suggestions n inputs.
Thanks in advance.