Configuring Route Policies; Routing Policy And Mpls - Alcatel-Lucent 7705 Configuration Manual

Configuring Route Policies

Configuring Route Policies
Route policies are used to manage the label database for MPLS and to control entries to the
routing table for dynamic routing.
See
the MPLS label database.
For routing, the 7705 SAR supports two databases to store routes. The routing database (RIB)
is composed of the routing information learned by the routing protocols, including static
routes. The forwarding database (FIB) is composed of the routes actually used to forward
traffic through a router. In addition, link-state databases are maintained by interior gateway
protocols (IGPs) such as OSPF and IS-IS. Refer to the 7705 SAR OS Routing Protocols
Guide for information on OSPF and IS-IS.
Routing protocols calculate the best route to each destination and place these routes in the
forwarding table. The routes in the forwarding table are used to forward IP packets to
neighbors.
As an example, operators can configure a routing policy that will not place routes associated
with a specific origin in the routing table. These routes will not be used to forward data
packets and these routes are not advertised by the routing protocol to neighbors.
Routing policies control the size and content of the routing tables, the routes that are
advertised, and the best route to take to reach a destination. Careful planning is essential to
implement route policies that can affect the flow of routing information throughout the
network. Before configuring and applying a route policy, operators should develop an overall
plan and strategy to accomplish their intended routing actions.
There are no default route policies. Each policy must be created explicitly and applied. Policy
parameters are modifiable.

Routing Policy and MPLS

Route policies can be used to manage the label database for MPLS.
When used to manage the label database, route policies can be configured to determine which
labels should be learned or advertised; for example, labels from a specified neighbor can be
added to the label information base (LIB), while labels advertised by certain other neighbors
can be discarded. Label learning of MPLS packets and, as a result, how the MPLS packets
are forwarded, are based on the defined policies, if there are any. If no route policies are
defined, all advertised labels received from neighbors are learned and placed in the LIB.
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Routing Policy and MPLS for information on how routing policies can be used to manage
7705 SAR OS Router Configuration Guide