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BGPPrivileged EXEC

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.

Syntax·Privileged EXEC
clear ip bgp *

When to Use This Command

  • After making major BGP policy changes (e.g., route maps, prefix lists) that require all sessions to reset to take effect.
  • When troubleshooting BGP convergence issues and need to force a full route refresh from all peers.
  • After upgrading or rebooting a BGP router to re-establish all BGP sessions and rebuild the routing table.
  • When testing BGP failover scenarios by simulating a complete BGP reset.

Command Examples

Basic BGP session reset

clear ip bgp *

No output is displayed. The command immediately resets all BGP sessions. Use 'show ip bgp summary' to verify sessions re-establish.

Verifying after reset

show ip bgp summary
BGP router identifier 192.168.1.1, local AS number 65001
BGP table version is 1, main routing table version 1
Neighbor        V           AS MsgRcvd MsgSent   TblVer  InQ OutQ Up/Down  State/PfxRcd
10.0.0.2        4        65002       0       0        0    0    0 never    Active
10.0.0.3        4        65003       0       0        0    0    0 never    Active

After 'clear ip bgp *', all neighbors show 'Active' state and zero messages. The 'Up/Down' column shows 'never' indicating sessions are being re-established. Wait for them to reach 'Established' state.

Understanding the Output

The 'clear ip bgp *' command produces no direct output. To verify its effect, use 'show ip bgp summary'. Key fields: 'Neighbor' – peer IP; 'V' – BGP version; 'AS' – neighbor's AS number; 'MsgRcvd/MsgSent' – messages exchanged; 'TblVer' – table version; 'InQ/OutQ' – queued messages; 'Up/Down' – time since last state change; 'State/PfxRcd' – current session state or number of prefixes received. After a clear, all neighbors should show 'Active' or 'Connect' and eventually 'Established'. If any neighbor remains in 'Idle' or 'Active', there may be a connectivity or configuration issue.

CCNA Exam Tips

1.

CCNA exam tip: 'clear ip bgp *' is disruptive; it resets all BGP sessions. Use 'clear ip bgp <neighbor>' to reset a single session.

2.

CCNA exam tip: After clearing BGP, the router sends OPEN messages to re-establish sessions. The 'Up/Down' time resets to 'never' until the session comes up.

3.

CCNA exam tip: BGP route flapping can be caused by frequent clears. Use 'bgp dampening' to mitigate instability.

4.

CCNA exam tip: The command does not affect the BGP configuration; only runtime sessions and the routing table are cleared.

Common Mistakes

Mistake 1: Using 'clear ip bgp *' for minor policy changes; it causes unnecessary network disruption. Use 'clear ip bgp * soft' for a soft reset instead.

Mistake 2: Forgetting to verify BGP sessions after the clear; sessions may fail to re-establish due to misconfiguration.

Mistake 3: Assuming the command clears only the BGP table; it also resets all TCP sessions with BGP peers.

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 summary

Displays a summary of the BGP neighbor status and prefix counts, used to quickly verify BGP peering and routing table health.

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