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Phantom routers can exist throughout a network. The MAC [Media Access Control] address and the IP [Internet Protocol] addresses are passed among routers. This creates a virtual router called a phantom router. It works like this:

• One router is designated as the active router and the other as the phantom/standby router. The active router routes packets for the phantom/standby router.

• Route table/list updates are sent via HSRP [Hot Standby Routing Protocol] via Hello messages.
• If the phantom/standby router does not receive Hello packets, it assumes that the active router has failed and begins routing packets. Proxy ARP [Address Resolution Protocol] is the default feature on Cisco routers. This is a simple means of creating fault-tolerant networks with one or more additional routers. Each router can respond to user/workstation requests if the router can reach (send/receive) the IP address. Each workstation can dynamically access multiple routers from the LAN. If any router fails, the workstation can immediately access other routers on the Internetwork (network). Users can access this feature by changing their Windows setting default gateway. MHSRP is for multi-group (router) HSRP.

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