Ospf Dynamic Cost; Ospf Limitations - Avaya G250 Administration

In OSPF, routers use link-state updates to send routing information to all nodes in a network by
calculating the shortest path to each node. This calculation is based on a topography of the
network constructed by each node. Each router sends that portion of the routing table that
describes the state of its own links, and it also sends the complete routing structure
(topography).
You can configure route redistribution between OSPF, RIP, and static routes. With route
redistribution, you can configure the G250/G350 to redistribute routes learned from one protocol
into the domain of the other routing protocol. For more information, see
page 351.

OSPF dynamic cost

An OSPF interface on the G250/G350 can dynamically set a Cost. The Cost represents the
price assigned to each interface for purposes of determining the shortest path.
By default the OSPF interface Cost is calculated based on the interface bandwidth, according to
the following formula:
Cost = 100,000/bandwidth (in kbps)
The result is that the higher the bandwidth, the lower the Cost.
To manually configure the Cost of an OSPF interface, use the ip ospf cost command from
the interface context. By using this option, dynamic bandwidth updates do not change the Cost.
Use the no ip ospf cost command to return to dynamic cost calculation on an interface.
Use the bandwidth command from the Interface context to manually adjust the interface's
bandwidth If Cost is being determined dynamically, this configured bandwidth and not the actual
interface bandwidth, is used to calculate Cost.

OSPF limitations

You can configure the G250/G350 as an OSPF Autonomous System Boundary Router (ASBR)
using route redistribution. The G250/G350 can be installed in the OSPF backbone area (area
0.0.0.0) or in any OSPF area that is part of a multiple areas network. However, the G250/G350
cannot be configured to be an OSPF area border router itself.
The G250/G350 supports the ECMP equal-cost multipath (ECMP) feature which allows load
balancing by splitting traffic between several equivalent paths.
While you can activate OSPF with default values for each interface using a single command,
you can configure many of the OSPF parameters.
Configuring OSPF
Route redistribution
Issue 1.1 June 2005
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