3Com Switch 7750 Configuration Guide Guide

302 CHAPTER 34: OSPF CONFIGURATION
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■ The import-route command cannot import the default route. To import the
default route, you must use the default-route-advertise command.
■ The filtering of advertised routes by OSPF means that OSPF only converts the
external routes meeting the filter criteria into Type-5 or Type-7 LSAs and
advertises them.
■ When enabling OSPF to import external routes, you can also configure the
defaults of some additional parameters, such as cost, number of routes, tag,
and type. A route tag can be used to identify protocol-related information.
OSPF Network
Adjustment and
Optimization
You can adjust and optimize an OSPF network in the following aspects:
■ By changing the OSPF packet timers, you can adjust the convergence speed of
the OSPF network and the network load brought by OSPF packets. On some
low-speed links, you need to consider the delay experienced when the
interfaces transmit LSAs.
■ By Adjusting SPF calculation interval, you can mitigate resource consumption
caused by frequent network changes.
■ In a network with high security requirements, you can enable OSPF
authentication to enhance OSPF network security.
■ In addition, OSPF supports network management. You can configure the
binding of the OSPF MIB with an OSPF process and configure the Trap message
transmission and logging functions.
Configuration
Prerequisites
Before adjusting and optimizing an OSPF network, perform the following tasks:
■ Configuring the network layer addresses of interfaces so that the adjacent
nodes are reachable to each other at the network layer
■ Configuring basic OSPF functions
Configuring OSPF Timers The Hello intervals for OSPF neighbors must be consistent. The value of Hello
interval is in inverse proportion to route convergence speed and network load.
The dead time on an interface must be at least four times of the Hello interval on
the same interface.
After a router sends an LSA to a neighbor, it waits for an acknowledgement
packet from the neighbor. If the router receives no acknowledgement packet from
the neighbor within the retransmission interval, it retransmits the LSA to the
neighbor.
Tabl e 225 Configure OSPF timers
Operation Command Description
Enter system view system-view -
Enter interface view
interface interface-type
interface-number
-