Aggregating Routes; Redistributing Routes - Lenovo Flex System Fabric CN4093 Application Manual

Aggregating Routes

Redistributing Routes

© Copyright Lenovo 2017
Aggregation is the process of combining several different routes in such a way that
a single route can be advertised, which minimizes the size of the routing table. You
can configure aggregate routes in BGP either by redistributing an aggregate route
into BGP or by creating an aggregate entry in the BGP routing table.
To define an aggregate route in the BGP routing table, use the following
commands:
CN 4093(config)# router bgp
CN 4093(config-router-bgp)# aggregate-address <1‐16> <IPv4 address> <mask>
CN 4093(config-router-bgp)# aggregate-address <1‐16> enable
CN 4093(config-router-bgp)# exit
An example of creating a BGP aggregate route is shown in "Default Redistribution
and Route Aggregation Example" on page
In addition to running multiple routing protocols simultaneously, Enterprise NOS
software can redistribute information from one routing protocol to another. For
example, you can instruct the switch to use BGP to re‐advertise static routes. This
applies to all of the IP‐based routing protocols.
You can also conditionally control the redistribution of routes between routing
domains by defining a method known as route maps between the two domains.
For more information on route maps, see "What is a Route Map?" on page
Redistributing routes is another way of providing policy control over whether to
export OSPF routes, fixed routes, and static routes. For an example configuration,
see "Default Redistribution and Route Aggregation Example" on page
Default routes can be configured using the following methods:
Import

 Originate—The router sends a default route to peers if it does not have any
default routes in its routing table.
 Redistribute—Default routes are either configured through the default gateway
or learned via other protocols and redistributed to peer routers. If the default
routes are from the default gateway, enable the static routes because default
routes from the default gateway are static routes. Similarly, if the routes are
learned from another routing protocol, make sure you enable that protocol for
redistribution.
 None
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Chapter 29: Border Gateway Protocol
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