Router Identification Designation in OSPF

• Microsoft Windows NT Server version 4.0
• Microsoft Routing and Remote Access Service Update for Windows NT Server 4.0

SUMMARY

Each router running Open Shortest Path First (OSPF) in an Autonomous System (AS) is assigned a 32-bit unique identifier called a router ID. Although it looks like an IP address, it is only used to identify the router and is not an IP address.

MORE INFORMATION

The router ID is used to identify the router in an Autonomous System and is advertised in the OSPF Hello packets sent between routers. Some OSPF configuration information is determined by the highest router ID. In the case of a tie when determining the designated router in an AS, the highest router ID takes precedence.

Although the router need not have any relationship to IP addresses on the router, it is generally accepted practice to make the router ID either the highest or lowest IP address on the router. If the router ID is changed the OSPF protocol should be reinitialized.