598 CHAPTER 19: OPEN SHORTEST PATH FIRST (OSPF)
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ip ospf policy modify Modifies an existing OSPF routing policy.
Valid Minimum Abbreviation
ip o po m
Important Considerations
■The system assigns an index number to each policy and takes into
account all route policies, Routing Information P rotocol (RIP) and OSPF,
that are set on the system.
■There are certain conditions associated with import and export
policies. See the Implementation Guide for your system for more
information.
■Your system has one unified IP routing table. Routing policies allow
you to control the flow of information amo ng the network, the
protocols, and the routing tables on your system.
■There are two classes of routing policies:
■Import policies — Control which OSPF non-self-originated
external routes are stored in the routing table. OSPF import policies
control only what the local router uses. They do not affect the
propagation of non-self-originated external routes to other routers.
■Export policies — Used on OSPF boundary routers to control
which self-originated external routing updates are placed in the
link-state database for propagation over the netwo rk. In this way,
export policies govern what other routers le arn with regard to the
local boundary router’s self-originated information.
■You can set up an IP RIP or OSPF import or export policy to ac cept or
advertise the default route, as long as the default route exists in the
routing table. When you define a policy, you are always prompted for
the route subnet mask after the route address, even though you
specify the wildcard route address of 0.0.0.0.
Specify a route subnet mask as follows:
■If you want the wildcard subnet mask for all routes, use the default
subnet mask (0.0.0.0).
■If you want the default route (not all routes), enter
255.255.255.255.
■For more information about IP routing policies, see the
Implementation Guide for your system.