Allied Telesis AT-8824 Guía de instalación descargar pdf (Pagina 134)

2-12 Release Note

Software Version 2.7.5

C613-10454-00 REV A

Example comparing

AS path filter and

route map

Compare this configuration, which uses an AS path list in a path filter:

add ip aspathlist=2 entry=1 exclude="^$"

add ip aspathlist=2 entry=2 include="15557"

set /jointfilesconvert/427458/bgp peer=192.168.200.201 outpathfilter=2

with this configuration, which uses a route map and matches on AS path list:

add ip aspathlist=2 entry=1 include="^$"

add ip aspathlist=2 entry=2 exclude="15557"

add ip routemap=outdef3 entry=1 action=exclude match

aspathlist=2

set /jointfilesconvert/427458/bgp peer=192.168.200.201 outroutemap=outdef3

With both these configurations, the router or switch drops update messages

with empty AS paths, and advertises update messages with an AS path

containing 15557. For the route map to achieve this (the second configuration):

■ The AS path list has to include empty paths, so that the empty path

matches the path list, and therefore is included into the route map’s action

of dropping packets that match the path list.

■ The AS path list has to exclude updates whose AS path includes 15557.

This excludes those updates from the route map’s action of dropping

packets that match the path list, so they are not dropped.

Matching on

community list

An entry that matches on communitylist lets you select or discard routes that

belong to a particular community.

To do this, first create a community list and add entries to it by using one of the

commands:

add ip communitylist=1..99 [entry=1..4294967295]

include={internet|noexport|noadvertise|

noexportsubconfed|aa:xx}[,...]

add ip communitylist=1..99 [entry=1..4294967295]

exclude={internet|noexport|noadvertise|

noexportsubconfed|aa:xx}[,...]

Then use the community list in the match clause of a route map by using the

command:

add ip routemap=routemap entry=1..4294967295

[action={include|exclude}] match community=1..99

[exact={no|yes}]

Note that the action (include/exclude) of the community list and of the route

map entry are separate. This leads to the same behaviour as the distinction

between the AS path list include/exclude parameters and the route map entry

action. For a discussion of the distinction between these two include/exclude

actions, see the table in “Matching on AS path list” on page 2-10.

If you specify exact=yes, an update message only matches the route map entry

if its community attribute contains all the communities specified in the

community list, and no other communities. If you specify exact=no, which is

the default, then the set of communities in the attribute list of the update

message must contain all the communities in the specified community list, but

can also contain other communities.

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