Attaching An Area To A Network; Interface Cost; Electing The Designated Router And Backup - Lenovo Flex System Fabric CN4093 Application Manual

Attaching an Area to a Network

Interface Cost

Electing the Designated Router and Backup

© Copyright Lenovo 2015
 Multi‐octet (IP address): Placing the area number in the last octet (0.0.0.n)
Some OSPF vendors express the area ID number in multi‐octet format. For
example, "area 0.0.0.2" represents OSPF area 2 and can be specified directly
on the CN4093 as "area­id 0.0.0.2".
On the CN4093, using the last octet in the area ID, "area 1" is equivalent to
"area­id 0.0.0.1".
Note: Although both types of area ID formats are supported, be sure that the area
IDs are in the same format throughout an area.
Once an OSPF area has been defined, it must be associated with a network. To
attach the area to a network, you must assign the OSPF area index to an IP interface
that participates in the area. The commands are as follows:
CN4093(config)# interface ip
CN4093(config­ip­if)# ip ospf area
CN4093(config­ip­if)# exit
For example, the following commands could be used to configure IPv4 interface 14
for a presence on the IPv4 10.10.10.1/24 network, to define OSPF area 1, and to
attach the area to the network:
CN4093(config)# router ospf
CN4093(config­router­ospf)# area 1 area­id 0.0.0.1
CN4093(config­router­ospf)# area 1 enable
CN4093(config­router­ospf)# enable
CN4093(config­router­ospf)# exit
i
CN4093(config)# nterface ip 14
CN4093(config­ip­if)# ip address 10.10.10.1 255.255.255.0 enable
CN4093(config­ip­if)# ip ospf area 1
CN4093(config­ip­if)# ip ospf enable
Note: OSPFv2 supports IPv4 only. IPv6 is supported in OSPFv3 (see
Implementation in Lenovo N/OS" on page
The OSPF link‐state algorithm (Dijkstra's algorithm) places each routing device at
the root of a tree and determines the cumulative cost required to reach each
destination. Usually, the cost is inversely proportional to the bandwidth of the
interface. Low cost indicates high bandwidth. You can manually enter the cost for
the output route with the following command:
CN4093(config­ip­if)# ip ospf cost <cost value (1‐65535)>
In any area with more than two routing devices, a Designated Router (DR) is
elected as the central contact for database exchanges among neighbors, and a
Backup Designated Router (BDR) is elected in case the DR fails.
<interface number>
<area index>
444).
"OSPFv3
429
Chapter 31: OSPF