The router ID uniquely identifies the router within an AS. In OSPF, routing information is exchanged between autonomous systems, groups of networks that share routing information. It can be set to be the same as the loopback (system interface) address. Subscriber services also use this address as far-end router identifiers when service distribution paths (SDPs) are created. The router ID is used by both OSPF and BGP routing protocols. A router ID can be derived by:
defining the value in the config>router router-id context
defining the system interface in the config>router>interface ip-int-name context (used if the router ID is not specified in the config>router router-id context)
inheriting the last four bytes of the MAC address
on the BGP protocol level, a BGP router ID can be defined in the config>router>bgp router-id context and is only used within BGP
defining a router ID when creating an OSPF instance config>router>ospf [instance-id] [router-id]
When configuring a new router ID, protocols are not automatically restarted with the new router ID. The next time a protocol is (re) initialized the new router ID is used. An interim period of time can occur when different protocols use different router IDs. To force the new router ID, issue the shutdown and no shutdown commands for each protocol that uses the router ID or restart the entire router.
It is possible to configure an SR OS to operate with an IPv6 only BOF and no IPv4 system interface address. When configured in this manner, the operator must explicitly define IPv4 router IDs for protocols such as OSPF and BGP as there is no mechanism to derive the router ID from an IPv6 system interface address.
The following displays a router ID configuration example:
A:ALA-B>config>router# info
#------------------------------------------
# IP Configuration
#------------------------------------------
interface "system"
address 10.10.10.104/32
exit
interface "to-103"
address 10.0.0.104/24
port 1/1/1
exit
autonomous-system 100
router-id 10.10.10.104
...
#------------------------------------------
A:ALA-B>config>router#