The rules for the election and update of router IDs are as follows:
1. If the router ID is configured through the router id command, set the router ID according to the configuration result.
2. If the router ID is not configured through the router id command and loopback interfaces that are configured with IP addresses exist, set the router ID to the maximum IP address among IP addresses of these loopback interfaces.
3. If the router ID is not configured through the router id command and no loopback interface configured with the IP address exists, set the router ID to the maximum IP address among IP addresses of other interfaces (irrespective of whether the interface is UP or DOWN).
4. The process of reelecting the router ID can be triggered only when the IP address of the interface that is set as the router ID is deleted or modified.
5. The change of the interface status does not result in the reelection of the router ID.
6. If the IP address of a loopback interface is configured after the router ID is set to the IP address of a non-loopback interface, the router ID reelection does not occur.
7. If an interface IP address whose value is larger than the value of the router ID, the router ID reelection does not occur.
8. The router ID may be set to a small interface IP address when the protocol wishes to obtain the router ID during system startup, because the route management (RM) module may have not obtained all information about interface IP addresses. This should not be regarded as a problem.
9. After the router ID is changed, the reset command needs to be executed to specify a new router ID for the protocol.
10. The router ID cannot be set to 0.0.0.0 or 255.255.255.255.