Edge-Core AS5700-54X, Справочное руководство CLI, Страница: 1001 / 1116

Chapter 29
| IP Routing Commands
Policy-based Routing for BGP
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Traffic engineering via longer prefixes is only effective when the longer prefixes
have a different next hop from the less specific prefix. Thus, past the point
where the next hops become identical, the longer prefixes provide no value
whatsoever. This command can be used to limit the radius of propagation of
more specific prefixes by adding a count of the ASes that may be traversed by
the more specific prefix.
◆
Private AS numbers [RFC1930] and confederation AS members [RFC3065]
found in the AS_PATH are not counted. AS numbers found within an AS_SET are
not counted and an entire AS_SET is counted as a single AS. Each instance of an
AS number that appears multiple times in an AS_PATH is counted.
If the AS_PATHLIMIT attribute is attached to a prefix by a private AS, then when
the prefix is advertised outside of the parent AS, the AS number contained in
the AS_PATHLIMIT attribute should be replaced by the AS number of the parent
AS.
Similarly, if the AS_PATHLIMIT attribute is attached to a prefix by a member of a
confederation, then when the prefix is advertised outside of the confederation
boundary, then the AS number of the confederation member inside of the
AS_PATHLIMIT attribute should be replaced by the confederation's AS number.
Example
Console(config)#route-map RD permit 8
Console(config-route-map)#match pathlimit as 5
Console(config-route-map)#on match goto 20
Console(config-route-map)#
match peer
This command sets the peer address to match in routing messages. Use the no
form to remove this entry from a route map.
Syntax
match peer { peer-address | local }
no match peer [ peer-address | local ]
peer-address – IP address of neighboring router sending routing messages.
local – Static or redistributed routes.
Command Mode
Route Map
Example
Console(config)#route-map RD permit 9
Console(config-route-map)#match peer 192.168.0.99
Console(config-route-map)#set weight 30
Console(config-route-map)#