Juniper Networks J2350 manual Backup Router, Loopback Address, Built-In Ethernet Interface Address

JUNOS Software with Enhanced Services Hardware Guide

Backup Router

You can specify a backup router to take over when the routing protocol process of the Services Router is not running, usually when the Services Router is booting, or if its routing protocol process has failed. Packets arriving at a Services Router in this situation are routed to the backup router. When the routing protocol process starts up again, the address of the backup router is removed from the routing and forwarding tables of the Services Router. The backup router must be located on the same subnet.

NOTE: To configure a backup router, you must use the CLI or J-Web configuration editor. You cannot configure a backup router with J-Web Quick Configuration.

Loopback Address

The loopback address is the IP address of the Services Router. The loopback address ensures that the router provides an IP address to management applications. Because it must always be available to hosts attempting to route packets to the router, the loopback address resides on an interface that is always active, known as the loopback interface (lo0.0). Setting a loopback address ensures that the router can receive packets addressed to the loopback address as long as the router is reachable though any entry (ingress) interface. In addition, applications such as NTP, RADIUS, and TACACS+ can use the loopback address as the source address for outgoing packets.

If you use the J-Web Set Up Quick Configuration page, you can either set a loopback address of your choice or have the loopback address automatically set to 127.0.0.1 when you click Apply or OK to commit the configuration.

Built-In Ethernet Interface Address

The built-in Gigabit Ethernet interfaces, ge-0/0/0through ge-0/0/3, on the front panel of the Services Router, are the interfaces through which you perform initial router setup. The examples in this guide use the ge-0/0/0interface as the management interface, but you can use any built-in Ethernet port for management. After the initial configuration is complete, you can attach the built-in Ethernet port that you are using for management purposes to the management network.

Before initial configuration, when the factory default configuration is active, the router attempts to perform autoinstallation by obtaining a router configuration through all its connected interfaces, including ge-0/0/0. The Services Router acts as a DHCP client out the built-in Ethernet interfaces.

If the Services Router does not find a DHCP server within a few seconds, it sets the address of ge-0/0/0to 192.168.1.1/24 and becomes a DHCP server out the ge-0/0/0interface.

NOTE: If the ge-0/0/1interface is being used, it is set to 192.168.2.1/24.

94■ Basic Connectivity Overview