06-01-2007 07:51 AM - edited 03-03-2019 05:15 PM
hi all,
Was trying to test this concept described in http://www.ccnalab.net/load_sharing_bgp.php
but after prepending my own AS, BGP still select only one default-route, did i missed something ?
======================================
ISP1:
router bgp 7374
no synchronization
bgp log-neighbor-changes
neighbor 120.1.1.1 remote-as 65001
neighbor 120.1.1.1 ebgp-multihop 2
neighbor 120.1.1.1 update-source Loopback0
neighbor 120.1.1.1 default-originate
neighbor 120.1.1.1 soft-reconfiguration inbound
neighbor 170.1.1.1 remote-as 4434
neighbor 170.1.1.1 ebgp-multihop 2
neighbor 170.1.1.1 update-source Loopback0
neighbor 170.1.1.1 soft-reconfiguration inbound
maximum-paths 2
no auto-summary
========================================
ISP2:
router bgp 1231
no synchronization
bgp log-neighbor-changes
neighbor 120.1.1.1 remote-as 65001
neighbor 120.1.1.1 ebgp-multihop 2
neighbor 120.1.1.1 update-source Loopback0
neighbor 120.1.1.1 default-originate
neighbor 120.1.1.1 soft-reconfiguration inbound
neighbor 170.1.1.1 remote-as 4434
neighbor 170.1.1.1 ebgp-multihop 2
neighbor 170.1.1.1 update-source Loopback0
neighbor 170.1.1.1 soft-reconfiguration inbound
no auto-summary
=========================================
CE1:
router bgp 65001
no synchronization
bgp log-neighbor-changes
network 202.1.1.0 mask 255.255.255.252
network 203.127.9.0
network 203.127.10.0
network 203.160.220.0 mask 255.255.255.252
network 203.160.220.4 mask 255.255.255.252
neighbor 100.1.1.1 remote-as 7374
neighbor 100.1.1.1 ebgp-multihop 2
neighbor 100.1.1.1 update-source Loopback0
neighbor 100.1.1.1 soft-reconfiguration inbound
neighbor 100.1.1.1 route-map prepend-AS-65001 in
neighbor 130.1.1.1 remote-as 1231
neighbor 130.1.1.1 ebgp-multihop 2
neighbor 130.1.1.1 update-source Loopback0
neighbor 130.1.1.1 soft-reconfiguration inbound
neighbor 130.1.1.1 route-map prepend-AS-65001 in
maximum-paths 4
no auto-summary
route-map prepend-AS-65001 permit 10
set as-path prepend 65001
=========================================
CE1#sh ip bgp
BGP table version is 7, local router ID is 203.127.10.1
Status codes: s suppressed, d damped, h history, * valid, > best, i - internal,
r RIB-failure, S Stale
Origin codes: i - IGP, e - EGP, ? - incomplete
Network Next Hop Metric LocPrf Weight Path
* 0.0.0.0 130.1.1.1 0 65001 1231 i
*> 100.1.1.1 0 65001 7374 i
*> 202.1.1.0/30 0.0.0.0 0 32768 i
*> 203.127.9.0 0.0.0.0 0 32768 i
*> 203.127.10.0 0.0.0.0 0 32768 i
*> 203.160.220.0/30 0.0.0.0 0 32768 i
*> 203.160.220.4/30 0.0.0.0 0 32768 i
CE1#
CE1#
=========================================
CE1#sh ip bgp 0.0.0.0
BGP routing table entry for 0.0.0.0/0, version 2
Paths: (4 available, best #3, table Default-IP-Routing-Table)
Multipath: eBGP
Advertised to non peer-group peers:
130.1.1.1
65001 1231
130.1.1.1 from 130.1.1.1 (130.1.1.1)
Origin IGP, localpref 100, valid, external
1231, (received-only)
130.1.1.1 from 130.1.1.1 (130.1.1.1)
Origin IGP, localpref 100, valid, external
65001 7374
100.1.1.1 from 100.1.1.1 (100.1.1.1)
Origin IGP, localpref 100, valid, external, best
7374, (received-only)
100.1.1.1 from 100.1.1.1 (100.1.1.1)
Origin IGP, localpref 100, valid, external
CE1#
========================================
Solved! Go to Solution.
06-01-2007 09:03 AM
Kian,
By default, BGP multipath will only work properly if both prefixes are received from the same AS. The trick of adding our AS doesn't work anymore as extra validations have been implemented to check that both aspaths are identical before using them both for BGP multipath.
This check can be relaxed via the following hidden command that was implemented in 12.3T.
router bgp
bgp bestpath as-path multipath-relax.
Note that it is ok to use this command for a stub site but it would certainly not be recommended for a transit network.
Hope this helps,
06-01-2007 09:03 AM
Kian,
By default, BGP multipath will only work properly if both prefixes are received from the same AS. The trick of adding our AS doesn't work anymore as extra validations have been implemented to check that both aspaths are identical before using them both for BGP multipath.
This check can be relaxed via the following hidden command that was implemented in 12.3T.
router bgp
bgp bestpath as-path multipath-relax.
Note that it is ok to use this command for a stub site but it would certainly not be recommended for a transit network.
Hope this helps,
06-02-2007 11:06 PM
Hi,
Does it mean that the in/out traffic are 50%, 50% for both links within the same ISP (one ISP with two links)
if we have two different ISPs, any solution for load balancing (50%, 50% in/out traffic)?
Best regards
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