show ip bgp summary
Displays a summary of the BGP neighbor status and prefix counts, used to quickly verify BGP peering and routing table health.
show ip bgp summaryWhen to Use This Command
- Check if BGP sessions to all neighbors are established after configuration changes.
- Monitor the number of prefixes received from each neighbor to detect route leaks or filtering issues.
- Troubleshoot BGP session flapping by reviewing state and uptime columns.
- Verify that the BGP router ID is correct and that the local AS number matches expectations.
Command Examples
Basic BGP summary with multiple neighbors
show ip bgp summaryBGP router identifier 10.1.1.1, local AS number 65001 BGP table version is 1234, main routing table version 1234 Neighbor V AS MsgRcvd MsgSent TblVer InQ OutQ Up/Down State/PfxRcd 192.168.1.2 4 65002 1234 1234 1234 0 0 2w0d 500 10.0.0.2 4 65003 5678 5678 5678 0 0 1d04h 200 172.16.0.2 4 65004 0 0 0 0 0 never Active
BGP router identifier: 10.1.1.1 (highest loopback or physical IP). Local AS: 65001. Table version: 1234 (increments with each change). Neighbor: IP of peer. V: BGP version (always 4). AS: remote AS. MsgRcvd/MsgSent: messages exchanged. TblVer: last table version sent. InQ/OutQ: queue depth (should be 0). Up/Down: time since session established or current state. State/PfxRcd: if established, shows number of prefixes received; otherwise shows state (Idle, Connect, Active, OpenSent, OpenConfirm, Established).
BGP summary with a down neighbor
show ip bgp summaryBGP router identifier 10.1.1.1, local AS number 65001 BGP table version is 1234, main routing table version 1234 Neighbor V AS MsgRcvd MsgSent TblVer InQ OutQ Up/Down State/PfxRcd 192.168.1.2 4 65002 1234 1234 1234 0 0 2w0d 500 10.0.0.2 4 65003 0 0 0 0 0 never Idle
The neighbor 10.0.0.2 is in Idle state, meaning the session is down. No messages have been exchanged (MsgRcvd/MsgSent = 0). This could be due to misconfiguration, network unreachability, or a BGP policy issue. The 'never' uptime indicates the session has never been established.
Understanding the Output
The output starts with the BGP router ID and local AS number. The table version shows the current BGP table version; if it increments rapidly, routes are flapping. The neighbor table lists each BGP peer. Key columns: 'Neighbor' (peer IP), 'V' (BGP version, always 4), 'AS' (remote AS), 'MsgRcvd/MsgSent' (message counts; should increase over time), 'TblVer' (last table version sent to neighbor), 'InQ/OutQ' (should be 0; non-zero indicates congestion), 'Up/Down' (time since session established or current state), 'State/PfxRcd' (if established, shows number of prefixes received; if not, shows state: Idle, Connect, Active, OpenSent, OpenConfirm). A healthy session shows 'Established' or the prefix count. Watch for 'Active' (peer not responding) or 'Idle' (administratively down or misconfiguration). A sudden drop in prefix count may indicate filtering or route withdrawal.
CCNA Exam Tips
The 'State/PfxRcd' column shows either the BGP state or the number of prefixes received; if the session is up, it shows the prefix count, not 'Established'.
A neighbor in 'Active' state means the router is trying to connect but not receiving a response; common exam scenario: missing route to neighbor or ACL blocking TCP 179.
The 'Up/Down' column shows time since last state change; a short uptime indicates flapping, which could be due to mismatched hold timers or MTU issues.
The 'TblVer' column should be the same across all neighbors; if one neighbor has a lower version, it hasn't received the latest updates.
Common Mistakes
Assuming 'Active' means the session is up; it actually means the router is actively trying to connect.
Ignoring the 'InQ' and 'OutQ' columns; non-zero values indicate BGP update queue buildup, often due to slow peer or network congestion.
Misinterpreting the 'State/PfxRcd' column: when the session is established, it shows the prefix count, not the word 'Established'.
Related Commands
clear ip bgp *
Resets all BGP sessions and clears the BGP routing table, forcing a complete re-advertisement and re-learning of all BGP routes from all neighbors.
show ip bgp
Displays the BGP routing table, showing learned BGP routes and their attributes, used for troubleshooting BGP path selection and verifying route advertisement.
show ip bgp neighbors
Displays detailed information about BGP neighbor sessions, including state, timers, and advertised/received prefixes, used to verify BGP peering and troubleshoot neighbor relationships.
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