Monitoring and Troubleshooting BGP Neighbor Sessions

Transcription

1 Application Note Monitoring and Troubleshooting BGP Neighbor Sessions Juniper Networks, Inc North Mathilda Avenue Sunnyvale, CA USA or 888 JUNIPER Part Number: /02

2 Contents Purpose Procedure General Tips References Copyright 2002, Juniper Networks, Inc.

3 Purpose This application note provides procedures on monitoring and troubleshooting BGP neighbor sessions. It is intended to help network operations monitor and troubleshoot BGP neighbor sessions using Juniper Networks router tools. Procedure The following are procedures to monitor and troubleshoot BGP neighbor sessions. These procedures include and explain output from the Juniper Networks router. 1. To display information about BGP and its neighbors, use the show bgp summary command: show bgp summary Groups: 9 Peers: 11 Down Peers: 4 Table Tot Paths Act Paths Suppressed History Damp State Pending inet inet Peer AS InPkt OutPkt OutQ Flaps Last Up/Dwn State Active/ Received/Damped w1d13h 76365/76896/ /10991/ w5d13h 1/76896/0 0/10991/ w1d13h Idle w6d14h 5/7/0 0/0/ w4d22h 7/56/0 0/0/ w1d13h Idle w0d6h 1/1/0 0/0/ w1d13h Idle w6d23h 1/1/0 0/0/ d 20:14:18 2/3/0 0/0/ w0d18h Idle For the status of the BGP neighbor session, look at the State #Active/Received/Damped column for the BGP neighbor session in question (far right). If the BGP neighbor session is in the Established state, the column lists the number of paths received from the BGP neighbor, the number of paths received that are active and used for forwarding traffic, and the number of damped paths. If the BGP neighbor session is in a state other than Established, use the ping and show route commands to verify network connectivity to the BGP neighbor. Copyright 2002, Juniper Networks, Inc. 3

4 2. If there is network connectivity to the BGP neighbor but the BGP neighbor session is still not established, check the BGP neighbor configuration on the local and remote router. To check the BGP neighbor configuration on the local Juniper router, use the show bgp neighbor <address> command. show bgp neighbor Peer: AS Local: AS 333 Type: External State: Established Flags: <> Last State: OpenConfirm Last Event: RecvKeepAlive Last Error: Hold Timer Expired Error Export: [ deny-routes our-routes ] Import: [ Client_A.AS65444 set-local-pref ] Options: <Preference HoldTime Dampening Keepalive> Keepalive interval: 30 Holdtime: 90 Preference: 170 Number of flaps: 263 Error: "Hold Timer Expired Error" Sent: 3 Recv: 0 Error: "Cease" Sent: 258 Recv: 0 Peer ID: Local ID: Active Holdtime: 90 NLRI advertised by peer: NLRI for this session: unicast Table inet.0 Bit: 5 Active Prefixes: 5 Received Prefixes: 7 Suppressed due to damping: 0 Table inet.2 Bit: Active Prefixes: 0 Received Prefixes: 0 Suppressed due to damping: 0 Last traffic (seconds): Received 11 Sent 6 Checked 11 Input messages: Total Updates 8 Octets Output messages: Total Updates Octets Output Queue[0]: 0 Output Queue[1]: 0 Route Queue Timer: unset Route Queue: empty 3. To display the paths received from the BGP neighbor, use the show route receive-protocol bgp <address> terse command. user@router> show route receive-protocol bgp terse inet.0:77045 destinations,77045 routes(77007 active, 0 holddown, 53 hidden) Prefix Nexthop MED Lclpref AS path * / I * / I / I * / I * / I / I * / I inet.2:10995 destinations, routes (10995 active, 0 holddown, 0 hidden) Prefix Nexthop MED Lclpref AS path The entries that have a + or * in front of them are paths received that are active and used for forwarding traffic. If the number of paths received from the BGP neighbor is not correct, check the BGP neighbor configuration on the remote router. Copyright 2002, Juniper Networks, Inc. 4

5 4. If you want to determine why a route entry received from the BGP neighbor is not active, use the show route <destination prefix> detail command to display detailed route information. user@router> show route /24 detail inet.0: destinations, routes (77138 active, 0 holddown, 53 hidden) /24 (3 entries, 1 announced) *BGP Preference: 170/-81 Source: Nexthop: via so-0/3/0.0, selected State: <Active Int Ext> Local AS: 333 Peer AS: 333 Age: 2:36:23 Metric: 82 Metric2: 61 Task: BGP_ Announcement bits (3): 0-KRT 2-BGP BGP_Sync_Any AS path: I <Originator> Aggregator: Cluster list: Communities: 333: :889 BGP next hop: Localpref: 80 Router ID: BGP Preference: 170/-81 Source: Nexthop: via so-0/3/0.0, selected State: <NotBest Int Ext> Local AS: 333 Peer AS: 333 Age: 2:36:23 Metric: 82 Metric2: 61 Task: BGP_ AS path: I <Originator> Aggregator: Cluster list: Communities: 333: :889 BGP next hop: Localpref: 80 Router ID: BGP Preference: /-123 Nexthop: via t3-4/3/0.0, selected State: <Hidden Ext> Local AS: 333 Peer AS: Age: 1w6d 16:02:53 Task: BGP_ AS path: I Aggregator: Localpref: 100 Router ID: Look at the state flag for the path in question. If the flag is NotBest, the path is not the best path for the destination prefix. If the flag is Hidden, the path is not used because of routing policy, an unresolved next hop, or a damped path. Copyright 2002, Juniper Networks, Inc. 5

6 5. If a path from a BGP neighbor is not active because of routing policy, you can view the policy by typing show policy <policy-name>. The import and export policies applied to a BGP neighbor session is displayed in the show bgp neighbor <address> command output. user@router> show policy Client_A.AS65444 Policy Client_A.AS65444: from / / / / / / / / /24 then next policy ---- then reject 6. To display the routes advertised to the BGP neighbor, use the show route advertising-protocol bgp <address> command: user@router> show route advertising-protocol bgp inet.0: destinations, routes (77126 active, 0 holddown, 55 hidden) Prefix Nexthop MED Lclpref AS path /22 Self I /23 Self I / I /23 Self I /8 Self I /24 Self I /24 Self I /24 Self I /22 Self I /22 Self I /23 Self 0 I /23 Self I /24 Self I /24 Self I /20 Self 0 I /21 Self I /20 Self I /22 Self I /20 Self 0 I /20 Self I /20 Self I /19 Self I /18 Self I /17 Self I /19 Self 0 I Copyright 2002, Juniper Networks, Inc. 6

7 General Tips 7. Confirm: When you have resolved a BGP neighbor session problem, you can confirm that you are advertising and receiving the correct BGP routing information by using the show route advertising protocol bgp <address> command and the show route receive-protocol bgp <address> command. The following are two useful commands for troubleshooting BGP in general. 1. Type show route aspath-regex <regular-expression> to display entries in the routing table that match the specified BGP AS path regular expression. The following command displays any routes that has AS 8888 in the AS-PATH attribute. See the JUNOS Internet Software Configuration Guide for more information about AS path regular expression. user@router> show route aspath-regex ".* 8888.*" inet.0: destinations, routes (77153 active, 0 holddown, hidden) /19 *[BGP/170] 18:47:31, localpref 100 AS path: I > to via t3-5/1/1.0 [BGP] 18:46:56, localpref 100 AS path: I > to via t3-2/2/3.0 inet.2: destinations, routes (10908 active, 0 holddown, 0 hidden) iso.0: 1 destinations, 1 routes (1 active, 0 holddown, 0 hidden) 2. Type show route community <as-number:community-value> to display entries in the routing table that are members of a BGP community. The following command displays any routes that belong to the 333:300 community. user@router> show route community 333:300 inet.0: destinations, routes (77114 active, 0 holddown, hidden) /19 *[BGP/170] 4w4d 00:45:25, localpref 100 AS path: I > to via so-7/0/ /24 *[BGP/170] 01:27:39, MED 0, localpref 100 AS path: I > to via so-7/0/ /16 *[BGP/170] 2d 22:36:36, localpref 100, from AS path: 3456 I > to via so-0/0/0.0 [BGP/170] 2d 22:36:38, localpref 100, from AS path: 3456 I > to via so-0/0/ /30 *[BGP/170] 1w1d 07:47:14, localpref 100, from AS path: I > to via so-0/0/0.0 [BGP/170] 1w1d 07:47:14, localpref 100, from AS path: I > to via so-0/0/0.0 inet.2: destinations, routes (10906 active, 0 holddown, 0 hidden) iso.0: 1 destinations, 1 routes (1 active, 0 holddown, 0 hidden) Copyright 2002, Juniper Networks, Inc. 7

8 References JUNOS Internet Software Configuration Guide Copyright 2002, Juniper Networks, Inc. All rights reserved. Juniper Networks is registered in the U.S. Patent and Trademark Office and in other countries as a trademark of Juniper Networks, Inc. Broadband Cable Processor, G10, Internet Processor, JUNOS, JUNOScript, M5, M10, M20, M40, M40e, M160, M-series, T640, and T-series, are trademarks of Juniper Networks, Inc. All other trademarks, service marks, registered trademarks, or registered service marks are the property of their respective owners. All specifications are subject to change without notice. Juniper Networks assumes no responsibility for any inaccuracies in this document. Juniper Networks reserves the right to change, modify, transfer, or otherwise revise this publication without notice. Copyright 2002, Juniper Networks, Inc. 8