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You are here: Home / Juniper / BGP route selection doesnt respect local preference

BGP route selection doesnt respect local preference

June 2, 2016 by James Palmer

This article outlines the problem of BGP route selection broken in certain code version and how could one find that they are affected.

In 9.3 and 9.4, due to an uninitialized variable being used to select the best route among all routes for the same prefix, random route selection may happen.
This may lead a bgp running router to select the route with lowest local preference.

Following output is one symptom that would arise

[email protected]> show route 8.6.19.0/24 detail | no-more 

inet.0: 318921 destinations, 3155019 routes (318113 active, 10 holddown, 1880 hidden)
Restart Complete
8.6.19.0/24 (17 entries, 1 announced)
*BGP Preference: 170/-101
Next hop type: Indirect
Next-hop reference count: 249450
Source: 64.125.0.210
Next hop type: Router, Next hop index: 1048668
Next hop: 64.125.26.126 via xe-1/0/0.0 weight 0x1, selected
Label-switched-path mpr3.sjc7.us-to-mpr4.sjc7.us
Next hop: 64.125.27.86 via xe-0/0/0.0 weight 0x8001
Label-switched-path Bypass->64.125.26.126
Protocol next hop: 64.125.0.210
Indirect next hop: 124f25e8 1048650
State: <Active Int Ext>
Local AS: 6461 Peer AS: 6461
Age: 3d 15:15:39 Metric: 4294967294 Metric2: 3 
Task: BGP_6461.64.125.0.210+61872
Announcement bits (5): 0-KRT 2-RT 6-Aggregate 9-BGP RT Background 10-Resolve tree 4 
AS path: 7018 13535 I
AS path: Recorded
Communities: 6461:1114 6461:1666 6461:2501 6461:2601 6461:2722 6461:2863
Accepted
Localpref: 100
Router ID: 64.125.0.210
BGP Preference: 170/-101
Next hop type: Indirect
Next-hop reference count: 177766
Source: 64.125.0.233
Next hop type: Router, Next hop index: 1048773
Next hop: 64.125.27.90 via xe-1/1/0.0 weight 0x1, selected
Label-switched-path mpr3.sjc7.us-to-mpr1.lax12.us
Label operation: Push 379178
Next hop: 64.125.26.126 via xe-1/0/0.0 weight 0x8001
Label-switched-path Bypass->64.125.27.90->64.125.24.17
Label operation: Push 483253, Push 685360(top)
Protocol next hop: 64.125.0.233
Indirect next hop: 11a2e348 1048644
State: <NotBest Int Ext>
Inactive reason: Not Best in its group - IGP metric
Local AS: 6461 Peer AS: 6461
Age: 3d 15:15:39 Metric: 4294967294 Metric2: 522 
Task: BGP_6461.64.125.0.233+179
AS path: 7018 13535 I
AS path: Recorded
Communities: 6461:1114 6461:1666 6461:2501 6461:2601 6461:2713 6461:2869
Accepted
Localpref: 100
Router ID: 64.125.0.233
BGP Preference: 170/-101
Next hop type: Indirect
Next-hop reference count: 96204
Source: 64.125.0.208
Next hop type: Router, Next hop index: 1048665
Next hop: 64.125.27.90 via xe-1/1/0.0 weight 0x1, selected
Label-switched-path mpr3.sjc7.us-to-er2.ord7.us
Label operation: Push 370746
Next hop: 64.125.26.126 via xe-1/0/0.0 weight 0x8001
Label-switched-path Bypass->64.125.27.90->64.125.28.18
Label operation: Push 630338, Push 685312(top)
Protocol next hop: 64.125.0.208
Indirect next hop: 17d6ad20 1048726
State: <NotBest Int Ext>
Inactive reason: Not Best in its group - IGP metric
Local AS: 6461 Peer AS: 6461
Age: 3d 15:15:39 Metric: 4294967294 Metric2: 2278 
Task: BGP_6461.64.125.0.208+50988
AS path: 7018 13535 I
AS path: Recorded
Communities: 6461:1114 6461:1666 6461:2502 6461:2601 6461:2718 6461:2860
Accepted
Localpref: 100
Router ID: 64.125.0.208
BGP Preference: 170/-101
Next hop type: Indirect
Next-hop reference count: 121366
Source: 64.125.0.202
Next hop type: Router, Next hop index: 1048612
Next hop: 64.125.27.90 via xe-1/1/0.0 weight 0x1, selected
Label-switched-path mpr3.sjc7.us-to-er2.dfw2.us
Label operation: Push 334122
Next hop: 64.125.26.126 via xe-1/0/0.0 weight 0x8001
Label-switched-path Bypass->64.125.27.90->64.125.24.17
Label operation: Push 471285, Push 685360(top)
Protocol next hop: 64.125.0.202
Indirect next hop: 169a3f18 1048730
State: <NotBest Int Ext>
Inactive reason: Not Best in its group - IGP metric
Local AS: 6461 Peer AS: 6461
Age: 3d 15:15:39 Metric: 4294967294 Metric2: 2325 
Task: BGP_6461.64.125.0.202+59686
AS path: 7018 13535 I
AS path: Recorded
Communities: 6461:1114 6461:1666 6461:2501 6461:2601 6461:2707 6461:2814
Accepted
Localpref: 100
Router ID: 64.125.0.202
BGP Preference: 170/-101
Next hop type: Indirect
Next-hop reference count: 79123
Source: 64.125.0.220
Next hop type: Router, Next hop index: 1048784
Next hop: 64.125.27.90 via xe-1/1/0.0 weight 0x1, selected
Label-switched-path mpr3.sjc7.us-to-mpr4.atl6.us
Label operation: Push 379050
Next hop: 64.125.26.126 via xe-1/0/0.0 weight 0x8001
Label-switched-path Bypass->64.125.27.90->64.125.24.17
Label operation: Push 483237, Push 685360(top)
Protocol next hop: 64.125.0.220
Indirect next hop: 140429d8 1048685
State: <NotBest Int Ext>
Inactive reason: Not Best in its group - IGP metric
Local AS: 6461 Peer AS: 6461
Age: 3d 15:15:39 Metric: 4294967294 Metric2: 3031 
Task: BGP_6461.64.125.0.220+63498
AS path: 7018 13535 I
AS path: Recorded
Communities: 6461:1114 6461:1666 6461:2503 6461:2601 6461:2702 6461:2857
Accepted
Localpref: 100
Router ID: 64.125.0.220
BGP Preference: 170/-201
Next hop type: Indirect
Next-hop reference count: 2
Source: 64.124.201.186
Next hop type: Router, Next hop index: 936
Next hop: 64.124.201.186 via ge-11/0/0.0, selected
Protocol next hop: 64.124.201.186
Indirect next hop: b9acb28 1048880
State: <Ext>
Inactive reason: Local Preference
Local AS: 6461 Peer AS: 13535
Age: 3d 15:15:41 Metric2: 0 
Task: BGP_13535.64.124.201.186+61095
AS path: 13535 I
AS path: Recorded
Communities: 6461:1001 6461:2001 6461:2101 6461:2222 6461:2463
Accepted
Localpref: 200 >>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>> Route is inactive 
Router ID: 208.82.17.254
BGP Preference: 170/-101
Next hop type: Indirect
Next-hop reference count: 121357
Source: 64.125.0.194
Next hop type: Router, Next hop index: 1048599
Next hop: 64.125.27.90 via xe-1/1/0.0 weight 0x1, selected
Label-switched-path mpr3.sjc7.us-to-er2.lga5.us
Label operation: Push 788489
Next hop: 64.125.27.86 via xe-0/0/0.0 weight 0x8001
Label-switched-path Bypass->64.125.27.90->64.125.25.5
Label operation: Push 390441, Push 685408(top)
Protocol next hop: 64.125.0.194
Indirect next hop: 12841d20 1048766
State: <NotBest Int Ext> >>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>> inactive status
Inactive reason: Local Preference
Local AS: 6461 Peer AS: 6461
Age: 3d 15:15:39 Metric: 4294967294 Metric2: 3179 
Task: BGP_6461.64.125.0.194+179
AS path: 7018 13535 I
AS path: Recorded
Communities: 6461:1114 6461:1666 6461:2503 6461:2601 6461:2714 6461:2829
Accepted
Localpref: 100
Router ID: 64.125.0.194
BGP Preference: 170/-101
Next hop type: Indirect
Next-hop reference count: 178738
Source: 64.125.0.205
Next hop type: Router, Next hop index: 1048871
Next hop: 64.125.27.90 via xe-1/1/0.0 weight 0x1, selected
Label-switched-path mpr3.sjc7.us-to-er1.iad10.us
Label operation: Push 376778
Next hop: 64.125.27.86 via xe-0/0/0.0 weight 0x8001
Label-switched-path Bypass->64.125.27.90->64.125.25.5
Label operation: Push 594457, Push 685408(top)
Protocol next hop: 64.125.0.205
Indirect next hop: 14ffc0a8 1048687
State: <NotBest Int Ext>
Inactive reason: Local Preference
Local AS: 6461 Peer AS: 6461
Age: 3d 15:15:39 Metric: 4294967294 Metric2: 3618 
Task: BGP_6461.64.125.0.205+179
AS path: 7018 13535 I
AS path: Recorded
Communities: 6461:1114 6461:1666 6461:2503 6461:2601 6461:2711 6461:2858
Accepted
Localpref: 100
Router ID: 64.125.0.205
BGP Preference: 170/-101
Next hop type: Router, Next hop index: 772
Next-hop reference count: 261436
Source: 64.125.13.242
Next hop: 64.125.13.242 via xe-1/3/0.0, selected
State: <Ext>
Inactive reason: Interior > Exterior > Exterior via Interior
Local AS: 6461 Peer AS: 3356
Age: 8w4d 13:17:16 Metric: 4294967294 
Task: BGP_3356.64.125.13.242+53449
AS path: 3356 13535 I
AS path: Recorded
Communities: 6461:1666 6461:2501 6461:2601 6461:2722 6461:2863
Accepted
Localpref: 100
Router ID: 4.68.185.244
BGP Preference: 170/-101
Next hop type: Indirect
Next-hop reference count: 164080
Source: 64.125.0.201
Next hop type: Router, Next hop index: 1048756
Next hop: 64.125.27.90 via xe-1/1/0.0 weight 0x1, selected
Label-switched-path mpr3.sjc7.us-to-er1.dfw2.us
Label operation: Push 343946
Next hop: 64.125.26.126 via xe-1/0/0.0 weight 0x8001
Label-switched-path Bypass->64.125.27.90->64.125.24.17
Label operation: Push 473973, Push 685360(top)
Protocol next hop: 64.125.0.201
Indirect next hop: 14b42b28 1048758
State: <NotBest Int Ext>
Inactive reason: Not Best in its group - Interior > Exterior > Exterior via Interior
Local AS: 6461 Peer AS: 6461
Age: 3d 15:15:39 Metric: 4294967294 Metric2: 2324 
Task: BGP_6461.64.125.0.201+61936
AS path: 3356 13535 I
AS path: Recorded
Communities: 6461:1114 6461:1666 6461:2501 6461:2601 6461:2707 6461:2814
Accepted
Localpref: 100
Router ID: 64.125.0.201
BGP Preference: 170/-101
Next hop type: Indirect
Next-hop reference count: 165035
Source: 64.125.0.251
Next hop type: Router, Next hop index: 1048663
Next hop: 64.125.27.90 via xe-1/1/0.0 weight 0x1, selected
Label-switched-path mpr3.sjc7.us-to-mpr1.lhr1.uk
Label operation: Push 380010
Next hop: 64.125.27.86 via xe-0/0/0.0 weight 0x8001
Label-switched-path Bypass->64.125.27.90->64.125.25.5
Label operation: Push 600681, Push 685408(top)
Protocol next hop: 64.125.0.251
Indirect next hop: 12f25150 1048643
State: <NotBest Int Ext>
Inactive reason: Not Best in its group - Interior > Exterior > Exterior via Interior
Local AS: 6461 Peer AS: 6461
Age: 3d 15:15:40 Metric: 4294967294 Metric2: 7313 
Task: BGP_6461.64.125.0.251+179
AS path: 3356 13535 I
AS path: Recorded
Communities: 6461:1114 6461:1666 6461:2504 6461:2607 6461:2715 6461:2833
Accepted
Localpref: 100
Router ID: 64.125.0.251
BGP Preference: 170/-101
Next hop type: Indirect
Next-hop reference count: 164858
Source: 64.125.0.187
Next hop type: Router, Next hop index: 1048852
Next hop: 64.125.27.90 via xe-1/1/0.0 weight 0x1, selected
Label-switched-path mpr3.sjc7.us-to-er1.ams1.nl
Label operation: Push 378650
Next hop: 64.125.27.86 via xe-0/0/0.0 weight 0x8001
Label-switched-path Bypass->64.125.27.90->64.125.25.5
Label operation: Push 598009, Push 685408(top)
Protocol next hop: 64.125.0.187
Indirect next hop: 234f9d20 1048738
State: <NotBest Int Ext>
Inactive reason: Not Best in its group - Interior > Exterior > Exterior via Interior
Local AS: 6461 Peer AS: 6461
Age: 3d 15:15:39 Metric: 4294967294 Metric2: 7347 
Task: BGP_6461.64.125.0.187+179
AS path: 3356 13535 I
AS path: Recorded
Communities: 6461:1114 6461:1666 6461:2505 6461:2602 6461:2700 6461:2800
Accepted
Localpref: 100
Router ID: 64.125.0.187
BGP Preference: 170/-101
Next hop type: Indirect
Next-hop reference count: 152440
Source: 64.125.0.9
Next hop type: Router, Next hop index: 1048669
Next hop: 64.125.27.90 via xe-1/1/0.0 weight 0x1, selected
Label-switched-path mpr3.sjc7.us-to-mpr1.cdg11.fr
Label operation: Push 379946
Next hop: 64.125.27.86 via xe-0/0/0.0 weight 0x8001
Label-switched-path Bypass->64.125.27.90->64.125.25.5
Label operation: Push 600521, Push 685408(top)
Protocol next hop: 64.125.0.9
Indirect next hop: 14951d20 1048676
State: <NotBest Int Ext>
Inactive reason: Not Best in its group - Interior > Exterior > Exterior via Interior
Local AS: 6461 Peer AS: 6461
Age: 3d 15:15:40 Metric: 4294967294 Metric2: 8285 
Task: BGP_6461.64.125.0.9+51227
AS path: 3356 13535 I
AS path: Recorded
Communities: 6461:1114 6461:1666 6461:2504 6461:2603 6461:2704 6461:2873
Accepted
Localpref: 100
Router ID: 64.125.0.9
BGP Preference: 170/-101
Next hop type: Indirect
Next-hop reference count: 170419
Source: 64.125.0.8
Next hop type: Router, Next hop index: 1048579
Next hop: 64.125.27.90 via xe-1/1/0.0 weight 0x1, selected
Label-switched-path mpr3.sjc7.us-to-mpr1.fra4.de
Label operation: Push 377098
Next hop: 64.125.26.126 via xe-1/0/0.0 weight 0x8001
Label-switched-path Bypass->64.125.27.90->64.125.28.18
Label operation: Push 633410, Push 685312(top)
Protocol next hop: 64.125.0.8
Indirect next hop: 14b42150 1048678
State: <NotBest Int Ext>
Inactive reason: Not Best in its group - Interior > Exterior > Exterior via Interior
Local AS: 6461 Peer AS: 6461
Age: 3d 15:15:40 Metric: 4294967294 Metric2: 8329 
Task: BGP_6461.64.125.0.8+62578
AS path: 3356 13535 I
AS path: Recorded
Communities: 6461:1114 6461:1666 6461:2504 6461:2606 6461:2710 6461:2872
Accepted
Localpref: 100
Router ID: 64.125.0.8
BGP Preference: 170/-101
Next hop type: Router, Next hop index: 590
Next-hop reference count: 59506
Source: 64.125.12.50
Next hop: 64.125.12.50 via ge-11/0/9.0, selected
State: <Ext>
Inactive reason: Interior > Exterior > Exterior via Interior
Local AS: 6461 Peer AS: 3561
Age: 1w5d 17:31:05 Metric: 4294967294 
Task: BGP_3561.64.125.12.50+179
AS path: 3561 13535 I
AS path: Recorded
Communities: 6461:1666 6461:2501 6461:2601 6461:2722 6461:2863
Accepted
Localpref: 100
Router ID: 206.24.210.98
BGP Preference: 170/-101
Next hop type: Indirect
Next-hop reference count: 193527
Source: 64.125.0.207
Next hop type: Router, Next hop index: 1048692
Next hop: 64.125.27.90 via xe-1/1/0.0 weight 0x1, selected
Label-switched-path mpr3.sjc7.us-to-er1.ord7.us
Label operation: Push 377738
Next hop: 64.125.26.126 via xe-1/0/0.0 weight 0x8001
Label-switched-path Bypass->64.125.27.90->64.125.28.18
Label operation: Push 633666, Push 685312(top)
Protocol next hop: 64.125.0.207
Indirect next hop: 14ffc1f8 1048743
State: <Int Ext>
Inactive reason: IGP metric
Local AS: 6461 Peer AS: 6461
Age: 3d 15:15:39 Metric: 4294967294 Metric2: 2277 
Task: BGP_6461.64.125.0.207+50560
AS path: 3356 13535 I
AS path: Recorded
Communities: 6461:1114 6461:1666 6461:2502 6461:2601 6461:2718 6461:2860
Accepted
Localpref: 100
Router ID: 64.125.0.207
BGP Preference: 170/-101
Next hop type: Indirect
Next-hop reference count: 153332
Source: 64.125.0.206
Next hop type: Router, Next hop index: 1048788
Next hop: 64.125.27.90 via xe-1/1/0.0 weight 0x1, selected
Label-switched-path mpr3.sjc7.us-to-er2.iad10.us
Label operation: Push 373050
Next hop: 64.125.27.86 via xe-0/0/0.0 weight 0x8001
Label-switched-path Bypass->64.125.27.90->64.125.25.5
Label operation: Push 585801, Push 685408(top)
Protocol next hop: 64.125.0.206
Indirect next hop: 17a72b28 1048746
State: <NotBest Int Ext>
Inactive reason: Not Best in its group - IGP metric
Local AS: 6461 Peer AS: 6461
Age: 3d 15:15:39 Metric: 4294967294 Metric2: 3619 
Task: BGP_6461.64.125.0.206+179
AS path: 3356 13535 I
AS path: Recorded
Communities: 6461:1114 6461:1666 6461:2503 6461:2601 6461:2711 6461:2858
Accepted
Localpref: 100
Router ID: 64.125.0.206

 

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