Configuring IP Router Parameters
Page 22 7750 SR OS Router Configuration Guide
IP Addresses

Creating an IP Address Range

An IP address range can be reserved for exclusive use for services by defining the
config>router>service-prefix command. When the service is configured, the IP address
must be in the range specified as a service prefix. If no service prefix command is configured, then
no limitation exists.
Addresses in the range of a service prefix can be allocated to a network port unless the exclusive
parameter is used. Then, the address range is exclusively reserved for services.
When defining a range that is a superset of a previously defined service prefix, the subset will be
replaced with the superset definition. For example, if a service prefix exists for 10.10.10.0/24, and
a new service prefix is configured as 10.10.0.0/16, then the old address (10.10.10.0/24) will be
replaced with the new address (10.10.0.0/16).
When defining a range that is a subset of a previously defined service prefix, the subset will
replace the existing superset, providing addresses used by services are not affected; for example, if
a service prefix exists for 10.10.0.0/16, and a new service prefix is configured as 10.10.10.0/24,
then the 10.10.0.0/16 entry will be removed, provided that no services are configured that use
10.10.x.x addresses other than 10.10.10.x.
Router ID
The router ID, a 32-bit number, uniquely identifies the router within an autonomous system (AS)
(see Autonomous Systems (AS) on page 23). In protocols such as OSPF, routing information is
exchanged between areas, groups of networks that share routing information. It can be set to be the
same as the loopback address. The router ID is used by both OSPF and BGP routing protocols in
the routing table manager instance.
There are several ways to obtain the router ID. On each 7750 SR-Series router, the router ID can be
derived in the following ways.
• Define the value in the config>router router-id context. The value becomes the
router ID.
• Configure the system interface with an IP address in the config>router>interface
ip-int-name context. If the router ID is not manually configured in the
config>router router-id context, then the system interface acts as the router ID.
• If neither the system interface or router ID are implicitly specified, then the router ID is
inherited from the last four bytes of the MAC address.
• The router can be derived on the protocol level; for example, BGP.