ip vrf vrf-name: A global command that creates a VRF and enters VRF configuration mode.
ip vrf forwarding vrf-name: Interface or subinterface configuration command that assigns an interface or a subinterface to a VRF instance.
(Note: If the interface or subinterface already had an IP address assigned, this command will remove that address, and you will need to add it back.)
To configure a static router for a VRF, run the following:
Router(config)# ip route vrf <vrf-name> <network> <mask> {interface | next-hop}
EIGRP uses auto summarization of routes at major network boundaries. The exhibit shows the output of the command: show IP route EIGRP.
Neighbor relationship and authentication
The Hello and Dead timers must match for forming neighbour relationship.
The routers should be in the same Area to form neighbour relationship.
OSPF determines the router ID using the following criteria:
1. Use the address configured by the ospf router-id command
2. Use the highest numbered IP address of a loopback interface
3. Use the highest IP address of any physical interface
4. If no interface exists, set the router-ID to 0.0.0.0
Network types, area types, and router types
In an OSPF network, when a packet need to traverse from one area to another area to reach its destination, it is routed as below:
Source Area -> Source ABR -> Backbone Area -> Destination ABR -> Destination Area Routers
The sequence of steps followed in OSPF operation are as below:
1. Establish router adjacencies
2. Elect DR and BDR
3. Discover Routes
4. Choose appropriate routes for use
5. Maintain routing information.
"show ip ospf interface" can be used to check whether the interfaces have been configured properly. The command also gives the timer intervals, including hello intervals as well as neighbor adjacencies.
The following output provides a sample output of the command:
