Juniper JUNOSE 11.2.X BGP AND MPLS, Руководство по настройке

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in the routing table. As shown in Table 21 on page 134, default distances are provided for
each type of source from which a route can be learned.
Table 21: Default Administrative Distances for Route Sources
Default Distance Route Source
0 Connected interface
1 Static route
20 External BGP
110 OSPF
115 IS-IS
120 RIP
200 Internal BGP
255 Unknown
If the IP routing table contains several routes to the same prefix—for example, an OSPF
route and an IBGP route—the route with the lowest administrative distance is used for
forwarding.
By default, BGP propagates received BGP routes to EBGP routes only if the BGP route is
used for forwarding traffic—that is, if it is the route with the lowest administrative distance
in the IP forwarding table. However, you can modify this behavior by using the
bgp
advertise-inactive command. See “Advertising Inactive Routes” on page 61 for more
information.
You can use the distance bgp command to configure the administrative distance
associated with routes. If you choose to set an administrative distance, you must specify
a value for all three of the following types of routes:
• external—Administrative distance for BGP external routes. External routes are routes
for which the best path is learned from a BGP peer external to the AS. Acceptable
values are from 1 to 255. The default value is 20.
•
internal—Administrative distance for BGP internal routes. Internal routes are those
routes that are learned from a BGP peer within the same AS. Acceptable values are
from 1 to 255. The default value is 200.
•
local—Administrative distance for BGP local routes. Local routes are those routes
locally originated by BGP. BGP can locally originate routes if you issue the
network
command, if you configure redistribution into BGP, or by means of a non-AS-set
aggregate route. Acceptable values are from 1 to 255. The default value is 200.
Copyright © 2010, Juniper Networks, Inc. 134
JunosE 11.2.x BGP and MPLS Configuration Guide