BGP AS-PATH preferred route
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‎12-15-2017 01:39 PM
Hello, all!
Does anybody faced with issue, BGP routes with the same Weight and LPref and Summit is choose preferred route with larger AS-PATH?
EXOS 15.6.2
For example:
X670G2 # sh bgp
routes detail network 123.123.123.0/24
Routes:
Route: 123.123.123.0/24, Peer 1.2.3.4
Origin IGP, Next-Hop 1.2.3.4, LPref 500, MED 0
Weight 3000,
As-PATH: ( 45002 )
Community: 32808:1 32808:2 32808:3
Route: 123.123.123.0/24, Peer 5.6.7.8, BEST, Active
Origin IGP, Next-Hop 5.6.7.8, LPref 500, MED 0
Weight 3000,
As-PATH: ( 45001 45002 )
Community: 32808:1 32808:2 32808:3
Thank you!
Does anybody faced with issue, BGP routes with the same Weight and LPref and Summit is choose preferred route with larger AS-PATH?
EXOS 15.6.2
For example:
X670G2 # sh bgp
routes detail network 123.123.123.0/24
Routes:
Route: 123.123.123.0/24, Peer 1.2.3.4
Origin IGP, Next-Hop 1.2.3.4, LPref 500, MED 0
Weight 3000,
As-PATH: ( 45002 )
Community: 32808:1 32808:2 32808:3
Route: 123.123.123.0/24, Peer 5.6.7.8, BEST, Active
Origin IGP, Next-Hop 5.6.7.8, LPref 500, MED 0
Weight 3000,
As-PATH: ( 45001 45002 )
Community: 32808:1 32808:2 32808:3
Thank you!
5 REPLIES 5
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‎12-18-2017 06:07 AM
Thank you all for help!!!
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‎12-18-2017 12:56 AM
Hi Alexandr,
Just wondering if the next hop (1.2.3.4) is reachable (active) or not.
Just wondering if the next hop (1.2.3.4) is reachable (active) or not.
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‎12-18-2017 12:56 AM
Hello, David!
Both peers - 1.2.3.4. and 5.6.7.8 is reachable.
If one of them was unavailable, there would be no questions 
Thank you!
Both peers - 1.2.3.4. and 5.6.7.8 is reachable.
If one of them was unavailable, there would be no questions 
Thank you!
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‎12-16-2017 10:18 PM
To be more precise:
https://tools.ietf.org/html/rfc5065#section-5.3
"When comparing routes using AS_PATH length, CONFED_SEQUENCE and CONFED_SETs SHOULD NOT be counted."
If you don't remember what is CONFED_SEQ and CONFED_SET: https://tools.ietf.org/html/rfc5065#section-3
So, AS-Path is still used, but not with Member-AS. And you were looking only at member-AS, as the "()" stresses it in your output.
https://tools.ietf.org/html/rfc5065#section-5.3
"When comparing routes using AS_PATH length, CONFED_SEQUENCE and CONFED_SETs SHOULD NOT be counted."
If you don't remember what is CONFED_SEQ and CONFED_SET: https://tools.ietf.org/html/rfc5065#section-3
So, AS-Path is still used, but not with Member-AS. And you were looking only at member-AS, as the "()" stresses it in your output.
