AIS AI2524 Disable Default Ospf Metric Calculation Based on Bandwidth, Interface loopback

AI2524 Router Card User’s Manual

Force the Router ID Choice with a Loopback Interface

OSPF uses the largest IP address configured on the interfaces as its router ID. If the interface associated with this IP address is ever brought down, or if the address is removed, the OSPF process must re- calculate a new router ID and resend all its routing information over its interfaces.

If a loopback interface is configured with an IP address, the Cisco IOS software will use this IP address as its router ID, even if other inter faces have larger IP addresses. Since loopback interfaces never go down, greater stability in the routing table is achieved.

To configure an IP address on a loopback interface, perform thes tasks, starting in global configuration mode:

1.Create a loopback interface, which places you in interface config- uration mode

interface loopback 0

2.Assign an IP address to this interface. ip address address mask

Disable Default OSPF Metric Calculation Based on

Bandwidth

OSPF calculates the OSPF metric for an interface according to the bandwidth of the interface. To disable this feature, type this command in router configuration mode:

no ospf auto-cost-determination

Configure OSPF on Simplex Ethernet Interfaces

Because simplex interfaces between two devices on an Ethernet repre- sent only one network segment, for OSPF you must configure the transmitting interface to be a passive interface. This prevents OSPF from sending hello packets for the transmitting interface. Both devices are able to see each other via the hello packet generated for the receiv- ing interface.

To configure OSPF on simplex Ethernet interfaces, type this command in router configuration mode:

passive-interface type number

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