BigIron RX Series Configuration Guide 15753-1002253-01Basic IP parameters and defaults 7When parameter changes take effectMost IP parameters described in this chapter are dynamic. They take effect immediately, as soonas you enter the CLI command. You can verify that a dynamic change has taken effect bydisplaying the running configuration. To display the running configuration, enter the showrunning-config or write terminal command at any CLI prompt.To save a configuration change permanently so that the change remains in effect following asystem reset or software reload, save the change to the startup configuration file. Enter the writememory command from the Privileged EXEC level of any configuration level of the CLI.Changes to memory allocation require you to reload the software after you save the changes to thestartup configuration file. When reloading the software is required to complete a configurationchange, the procedure that describes the configuration change includes a step for reloading thesoftware.IP global parametersTable 43 lists the IP global parameters for the device, their default values, and where to findconfiguration information.TABLE 43 IP global parametersParameter Description Default See page...IP state The Internet Protocol, version 4 EnabledNOTE: You cannot disableIP.n/aIP address and masknotationFormat for displaying an IP address and its network maskinformation. You can enable one of the following:• Class-based format; example: 192.168.1.1 255.255.255.0• Classless Interdomain Routing (CIDR) format; example:192.168.1.1/24Class-basedNOTE: Changing thisparameter affectsthe display of IPaddresses, but youcan enter addressesin either formatregardless of thedisplay setting.page 161Router ID The value that routers use to identify themselves to other routerswhen exchanging route information. OSPF and BGP4 use routerIDs to identify routers. RIP does not use the router ID.The IP address configured onthe lowest-numberedloopback interface.If no loopback interface isconfigured, then thelowest-numbered IP addressconfigured on the device.page 182IP MaximumTransmission Unit(MTU)The maximum length an Ethernet packet can be without beingfragmented.1500 bytes for Ethernet IIencapsulation1492 bytes for SNAPencapsulationpage 181Address ResolutionProtocol (ARP)A standard IP mechanism that routers use to learn the MediaAccess Control (MAC) address of a device on the network. Therouter sends the IP address of a device in the ARP request andreceives the device’s MAC address in an ARP reply.Enabled page 187
