area x default-cost <Value>

Unanswered Question
sundar.palaniappan Fri, 03/23/2007 - 15:13

Ali,

See the responses below.

1)I Have to know where/when in OSPF We use the command area x default-cost

From CCO;

area default-cost

To specify a cost for the default summary route sent into a stub or not-so-stubby area (NSSA), use the area default-cost command in router configuration mode. To remove the assigned default route cost, use the no form of this command.

area area-id default-cost cost

no area area-id default-cost cost

Syntax Description

area-id

Identifier for the stub or NSSA. The identifier can be specified as either a decimal value or as an IP address.

cost

Cost for the default summary route used for a stub or NSSA. The acceptable value is a 24-bit number.

Defaults

cost: 1

Command Modes

Router configuration

Command History

Release

Modification

10.0

This command was introduced.

12.2(33)SRA

This command was integrated into Cisco IOS Release 12.2(33)SRA.

Usage Guidelines

The command is used only on an Area Border Router (ABR) attached to a stub or NSSA.

There are two stub area router configuration commands: the stub and default-cost options of the area command. In all routers and access servers attached to the stub area, the area should be configured as a stub area using the stub option of the area command. Use the default-cost option only on an ABR attached to the stub area. The default-cost option provides the metric for the summary default route generated by the ABR into the stub area.

Note To remove the specified area from the software configuration, use the no area area-id command (with no other keywords). That is, the no area area-id command removes all area options, such as area authentication, area default-cost, area nssa, area range, area stub, and area virtual-link.

Examples

The following example assigns a default cost of 20 to stub network 10.0.0.0:

interface ethernet 0

ip address 10.56.0.201 255.255.0.0

!

router ospf 201

network 10.0.0.0 0.255.255.255 area 10.0.0.0

area 10.0.0.0 stub

area 10.0.0.0 default-cost 20

---------------------------------------------------------------------------------------

2)why in OSPF The Metric-type 1 increment?

Setting the metric-type to 1 is useful when there are multiple paths/ABRs exist for the traffic leaving the network. The internal routers would be able to choose the optimal path via the closest ABR to reach the destination network. Metric type 1 would cause the cost of the route increment as it travels through every additional hop and thus any router with multiple path(s) to a network would choose the one with a lower cost/better metric. On the other had, with metric-type 2 the cost remains constant and the internal routers mayn't make the best choice of path. As you can see, metric-type 1 would be useful only when there are multiple ABRs exist in your network.

HTH

Sundar

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