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| 6.4 |  | HSRP Configuration |
| 6.4.2 |  | How HSRP addresses redundancy issues |

HSRP provides a way for end nodes to keep communicating between networks even if individual local routers become unavailable. HSRP routers on a LAN segment or VLAN communicate among themselves to designate three possible router states:

- active
- standby
- init

If an end node sends a packet to the virtual MAC address, the active router receives that packet and processes it. If an end node sends an ARP request the active router replies with the virtual MAC address. The routers participating in HSRP can be configured to respond with their burned-in (BIA) MAC address instead of a virtual MAC address.

In Figure , Anderson would be configured to use the virtual router as the default. Only the virtual router would appear in the Anderson configuration. Broadway would not be listed. Upon booting, the routers might elect Broadway as active router so that Broadway would deliver packets from Anderson. If Broadway or its LAN interface went offline, Central Park would take over as active router, continuing with the delivery of Anderson packets. The changes taking place in the network would remain transparent to Anderson. If a third HSRP router was added to the LAN segment, this router would begin to act as the new standby router but remain in the "init" state.

HSRP also works for proxy ARP. When an active HSRP router receives an ARP request for a node that is not on the local LAN it replies with the virtual MAC address. If the router that originally sent the ARP reply later loses its connection, the new active router can still deliver the traffic. Although HSRP works with proxy ARP configurations, it is not a recommended configuration due to administrative and security reasons.