314 Brocade ICX 6650 Layer 3 Routing Configuration Guide
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Optional BGP4 configuration tasks
When selecting a route from among different sources (BGP4, OSPF, RIP, static routes, and so on),
the software compares the routes on the basis of each route administrative distance. If the
administrative distance of the paths is lower than the administrative distance of paths from other
sources (such as static IP routes, RIP, or OSPF), the BGP4 paths are installed in the IP route table.
NOTE
The software will replace a statically configured default route with a learned default route if the
learned route administrative distance is lower than the statically configured default route distance.
However, the default administrative distance for static routes is changed to 1, so only
directly-connected routes are preferred over static routes when the default administrative distances
for the routes are used.
The following default administrative distances are found on the Brocade Layer 3 switch:
•Directly connected – 0 (this value is not configurable)
•Static – 1 (applies to all static routes, including default routes)
•EBGP – 20
•OSPF – 110
•RIP – 120
•IBGP – 200
•Local BGP – 200
•Unknown – 255 (the router will not use this route)
Lower administrative distances are preferred over higher distances. For example, if the router
receives routes for the same network from OSPF and from RIP, the router will prefer the OSPF route
by default. The administrative distances are configured in different places in the software. The
Layer 3 switch re-advertises a learned best BGP4 route to neighbors by default, regardless of
whether the route administrative distance is lower than other routes from different route sources to
the same destination.
•To change the EBGP, IBGP, and Local BGP default administrative distances, see the
instructions in this section.
•To change the default administrative distance for OSPF, refer to “Administrative distance” on
page207.
•To change the default administrative distance for RIP, refer to “Changing the administrative
distance” on page 146.
•To change the default administrative distance for static routes, refer to “Static routes
configuration” on page 45.
You can change the default EBGP, IBGP, and Local BGP administrative distances using either of the
following methods.
To change the default administrative distances for EBGP, IBGP, and Local BGP, enter a command
such as the following.
Brocade(config-bgp-router)#distance 180 160 40
Syntax: distance external-distance internal-distance local-distance
The external-distance sets the EBGP distance and can be a value from 1 through 255.
The internal-distance sets the IBGP distance and can be a value from 1 through 255.
The local-distance sets the Local BGP distance and can be a value from 1 through 255.