Example: Configuring an OSPF Router Identifier
This example shows how to configure an OSPF router identifier.
Before you begin:
Identify the interfaces on the routing device that will participate in OSPF. You must enable OSPF on all interfaces within the network on which OSPF traffic is to travel.
Configure the device interfaces. See the Interfaces Feature Guide for Security Devices
The router identifier is used by OSPF to identify the routing device from which a packet originated. Junos OS selects a router identifier according to the following set of rules:
By default, Junos OS selects the lowest configured physical IP address of an interface as the router identifier.
If a loopback interface is configured, the IP address of the loopback interface becomes the router identifier.
If multiple loopback interfaces are configured, the lowest loopback address becomes the router identifier.
If a router identifier is explicitly configured using the router-id address statement under the [edit routing-options] hierarchy level, the above three rules are ignored.
1. The router identifier behavior described here holds good even when configured under [edit routing-instances routing-instance-name routing-options] and [edit logical-systems logical-system-name routing-instances routing-instance-name routing-options] hierarchy levels.
2. If the router identifier is modified in a network, the link-state advertisements (LSAs) advertised by the previous router identifier are retained in the OSPF database until the LSA retransmit interval has timed out. Hence, it is strongly recommended that you explicitly configure the router identifier under the [edit routing-options] hierarchy level to avoid unpredictable behavior if the interface address on a loopback interface changes.
In this example, you configure the OSPF router identifier by setting its router ID value to the IP address of the device, which is 192.0.2.24.
CLI Quick Configuration
To quickly configure an OSPF router identifier, copy the following commands, paste them into a text file, remove any line breaks, change any details necessary to match your network configuration, copy and paste the commands into the CLI at the  hierarchy level, and then enter commit from configuration mode.
To configure an OSPF router identifier:
- Configure the OSPF router identifier by entering the [router-id] configuration value.user@host# set routing-options router-id 192.0.2.24
- If you are done configuring the device, commit the configuration.user@host# commit
Confirm your configuration by entering the show routing-options router-id command. If the output does not display the intended configuration, repeat the instructions in this example to correct the configuration.
After you configure the router ID and activate OSPF on the routing device, the router ID is referenced by multiple OSPF operational mode commands that you can use to monitor and troubleshoot the OSPF protocol. The router ID fields are clearly marked in the output.