Brocade Virtual ADX Switch and Router Guide (Supporting ADX v03.1.00) - Manual (Page 236)

222 Brocade Virtual ADX Switch and Router Guide
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Changing the default metric used for redistribution
8
Changing the default metric used for redistribution
The device can redistribute directly connected routes, static IP routes, and OSPF routes into BGP4.
By default, BGP4 uses zero (0) for direct connected routes and the metric (MED) value of IGP routes
in the IP route table. The MED is a global parameter that specifies the cost that will be applied to all
routes, if assigned, when they are redistributed into BGP4. When routes are selected, lower metric
values are preferred over higher metric values. The default, the BGP4 MED value is not assigned.
NOTE
OSPF also have default metric parameters. The parameters are set independently for each protocol
and have different ranges.
To change the default metric to 40, enter the following command.
Virtual ADX(config-bgp)# default-metric 40
Syntax: [no] default-metric value
The value indicates the metric and can be a value from 0 – 4294967295.
Changing the default metric used for route cost
By default, BGP4 uses the BGP MED value as the route cost when adding the route to the RTM.
However, you can configure BGP4 to use the IGP cost instead.
NOTE
It is recommended that you change the default to IGP cost only in mixed-vendor environments, and
that you change it on all Brocade devices in the environment.
To change the route cost default from BGP MED to IGP cost, enter a command such as the
following:
Virtual ADX(config-bgp-router)# install-igp-cost
Syntax: [no] install-igp-cost
Use the no form of the command to revert to the default of BGP MED.
Changing administrative distances
Because the device can learn about networks from various protocols, including the EBGP portion of
BGP4, and IGPs such as OSPF, the routes to a network may differ depending on the protocol from
which the routes were learned.
To select one route over another based on the source of the route information, the device can use
the administrative distances assigned to the sources. The administrative distance is a
protocol-independent metric that IP devices use to compare routes from different sources.
The device re-advertises a learned best BGP4 route to neighbors even when the route table
manager does not also select that route for installation in the IP route table. The best BGP4 route is
the BGP4 path that BGP4 selects based on comparison of the paths’ BGP4 route parameters.
Refer to
“How BGP4 selects a path for a route” on page 200.