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BGPPrivileged EXEC

show ip bgp [prefix]

Shows all BGP paths and attributes for a specific prefix to diagnose routing decisions.

Syntax·Privileged EXEC
show ip bgp <network-address>[/<prefix-length>]

When to Use This Command

  • Troubleshooting why a specific prefix is using one path over another.
  • Verifying BGP attributes (AS path, local pref, weight, MED) affecting path selection.
  • Confirming a prefix is in the BGP table and installed in the routing table.
  • Checking which peer originated a specific route.

Command Examples

Show all paths for a specific prefix

R1# show ip bgp 198.51.100.0/24
BGP routing table entry for 198.51.100.0/24, version 5
Paths: (2 available, best #1, table default)
  Advertised to update-groups:
     1
  100 200
    203.0.113.1 from 203.0.113.1 (203.0.113.1)
      Origin IGP, metric 0, localpref 100, valid, external, best
      rx pathid: 0, tx pathid: 0x0
  100 300 200
    203.0.113.5 from 203.0.113.5 (203.0.113.5)
      Origin IGP, metric 0, localpref 100, valid, external

Two paths exist. Path 1 via 203.0.113.1 has AS path '100 200' (shorter) and is marked 'best'. Path 2 via 203.0.113.5 has AS path '100 300 200' (longer). BGP prefers the shorter AS path, making path 1 best.

Prefix not in BGP table

R1# show ip bgp 10.0.0.0
% Network not in table

The prefix 10.0.0.0 is not in the BGP table — either no peer has advertised it, or it was filtered.

Understanding the Output

Key fields: '>' = best path, 'i' = iBGP source, 'e' = eBGP source. AS path is listed after the peer IP (shorter = preferred). 'localpref' (default 100) — higher wins. 'weight' (Cisco-proprietary) — higher wins, only affects local router. 'metric' = MED — lower wins. 'valid' = next hop is reachable. 'best' = selected path. The best path is installed in the IP routing table.

CCNA Exam Tips

1.

CCNA exam tip: BGP path selection order (simplified): weight > local-pref > locally originated > AS path length > origin code > MED > eBGP over iBGP > IGP metric to next hop.

2.

CCNA exam tip: 'show ip bgp' without an argument shows the entire BGP table — useful for seeing all prefixes.

3.

CCNA exam tip: A route marked 'valid' but not 'best' is in the table but not used — another path won the selection.

4.

CCNA exam tip: A route with no '>' is not installed in the routing table.

Common Mistakes

Mistake 1: Confusing 'show ip bgp' with 'show ip route' — BGP table and routing table are separate. A prefix can be in BGP but not installed if a better-admin-distance route exists.

Mistake 2: Forgetting that BGP only installs the BEST path into the routing table by default.

Mistake 3: Misreading AS path — path '100 200' means the traffic traverses AS 100 then AS 200; the origin AS is last (rightmost).

Related Commands

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.

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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