The Need for a First Hop Redundancy Protocol
Now back to the topic of this chapter. Of the designs shown so far in this chapter, only Figure 6-3’s design has two routers on the LAN of the left side of the figure, specifically the same VLAN and subnet. While having the redundant routers on the same subnet helps, the network needs to use an FHRP when these redundant routers exist.
To see the need and benefit of using an FHRP, first think about how these redundant routers could be used as default routers by the hosts in VLAN 10/subnet 10.1.1.0/24. The host logic will remain unchanged, so each host has a single default router setting. So, some design options for default router settings include the following:
All hosts in the subnet use R1 (10.1.1.9) ...