Juniper Networks J2320 manual Network Settings, Default Gateway, Backup Router, Loopback Address

J2320, J2350, J4350, and J6350 Services Router Getting Started Guide

Network Settings

A Domain Name System (DNS) server on the network maintains a database for resolving hostnames and IP addresses. Network devices can query the DNS server by hostnames rather than IP addresses. The router accesses the DNS servers that are added to the configuration to resolve hostnames in the order in which you list them.

If you plan to include your router in several domains, you can add these domains to the configuration so that they are included in a DNS search. When DNS searches are requested, the domain suffixes are appended to the hostnames.

Default Gateway

A default gateway is a static route that is used to direct packets addressed to networks not explicitly listed in the routing table. If a packet arrives at the Services Router with an address that the router does not have routing information for, the router sends the packet to the default gateway. The default gateway entry is always present in the routing and forwarding tables.

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.

132■ Basic Connectivity Overview