Cisco Systems 78-11741-02 Wireless Office Headset User Manual


 
Configuring OSPF
Changing the OSPF Administrative Distances
IPC-233
Cisco IOS IP Configuration Guide
Changing the OSPF Administrative Distances
An administrative distance is a rating of the trustworthiness of a routing information source, such as an
individual router or a group of routers. Numerically, an administrative distance is an integer from 0 to
255. In general, the higher the value, the lower the trust rating. An administrative distance of 255 means
the routing information source cannot be trusted at all and should be ignored.
OSPF uses three different administrative distances: intra-area, interarea, and external. Routes within an
area are intra-area; routes to another area are interarea; and routes from another routing domain learned
via redistribution are external. The default distance for each type of route is 110.
To change any of the OSPF distance values, use the following command in router configuration mode:
For an example of changing administrative distance, see the section “Changing OSPF Administrative
Distance Example” at the end of this chapter.
Configuring OSPF on Simplex Ethernet Interfaces
Because simplex interfaces between two devices on an Ethernet represent only one network segment, for
OSPF you must configure the sending interface to be a passive interface. This configuration prevents
OSPF from sending hello packets for the sending interface. Both devices are able to see each other via
the hello packet generated for the receiving interface.
To configure OSPF on simplex Ethernet interfaces, use the following command in router configuration
mode:
Configuring Route Calculation Timers
You can configure the delay time between when OSPF receives a topology change and when it starts a
shortest path first (SPF) calculation. You can also configure the hold time between two consecutive SPF
calculations. To do so, use the following command in router configuration mode:
Command Purpose
Router(config-router)# distance ospf {[intra-area dist1] [inter-area
dist2] [external dist3]}
Changes the OSPF distance values.
Command Purpose
Router(config-router)# passive-interface
interface-type interface-number
Suppresses the sending of hello packets through the specified
interface.
Command Purpose
Router(config-router)# timers spf spf-delay
spf-holdtime
Configures route calculation timers.