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network-bgp-diagnostics
// Diagnostics-only BGP troubleshooting patterns for neighbor state, route exchange, prefix policy, AS path inspection, and safe evidence collection.
// Diagnostics-only BGP troubleshooting patterns for neighbor state, route exchange, prefix policy, AS path inspection, and safe evidence collection.
| name | network-bgp-diagnostics |
| description | Diagnostics-only BGP troubleshooting patterns for neighbor state, route exchange, prefix policy, AS path inspection, and safe evidence collection. |
| origin | community |
Use this skill when a BGP session is down, flapping, established with missing routes, or advertising unexpected prefixes. The default workflow is read-only evidence collection; policy and reset actions belong in a reviewed change window.
show bgp summary
show bgp neighbors <peer>
show ip route <peer>
show tcp brief | include <peer>|:179
show logging | include BGP|<peer>
show running-config | section router bgp
show ip prefix-list
show route-map
Use platform-specific address-family commands when the device uses VRFs, IPv6, VPNv4, or EVPN. Do not assume global IPv4 unicast.
| State | First checks |
|---|---|
| Established with prefix count | Route exchange is up; inspect policy and table selection |
| Established with zero prefixes | Check inbound policy, max-prefix, advertised routes, and AFI/SAFI |
| Active | TCP session is not completing; check routing, source, ACLs, and peer reachability |
| Connect | TCP connection is in progress; check path and remote listener |
| OpenSent/OpenConfirm | TCP works; check ASN, authentication, timers, capabilities, and logs |
| Idle | Neighbor may be disabled, missing config, blocked by policy, or backoff timer |
ping <peer> source <local-source>
traceroute <peer> source <local-source>
show ip route <peer>
show bgp neighbors <peer> | include BGP state|Last reset|Local host|Foreign host
If the peer is sourced from a loopback, confirm both directions route to the loopback addresses and that the neighbor config uses the expected update source.
Avoid disabling ACLs or firewall policy as a diagnostic shortcut. Read hit counters, logs, and path state first.
show bgp neighbors <peer> advertised-routes
show bgp neighbors <peer> routes
show ip prefix-list <name>
show route-map <name>
show bgp <prefix>
Some platforms require additional configuration before received-routes is
available. Do not add that configuration during incident triage unless the
operator approves the change.
show bgp regexp _65001_
show bgp regexp ^65001$
show bgp <prefix>
show bgp neighbors <peer> advertised-routes | include Network|Path|<prefix>
Use AS-path regex carefully. _65001_ matches AS 65001 as a token. Plain
65001 can match longer ASNs or unrelated text.
import re
from typing import Any
BGP_SUMMARY_RE = re.compile(
r"^(?P<neighbor>\d{1,3}(?:\.\d{1,3}){3})\s+"
r"(?P<version>\d+)\s+"
r"(?P<remote_as>\d+)\s+"
r"(?P<msg_rcvd>\d+)\s+"
r"(?P<msg_sent>\d+)\s+"
r"(?P<table_version>\d+)\s+"
r"(?P<input_queue>\d+)\s+"
r"(?P<output_queue>\d+)\s+"
r"(?P<uptime>\S+)\s+"
r"(?P<state_or_prefixes>\S+)$",
re.M,
)
def parse_bgp_summary(raw: str) -> list[dict[str, Any]]:
rows = []
for match in BGP_SUMMARY_RE.finditer(raw):
state_or_prefixes = match.group("state_or_prefixes")
if state_or_prefixes.isdigit():
state = "Established"
prefixes_received = int(state_or_prefixes)
else:
state = state_or_prefixes
prefixes_received = None
rows.append({
"neighbor": match.group("neighbor"),
"remote_as": int(match.group("remote_as")),
"state": state,
"prefixes_received": prefixes_received,
"uptime": match.group("uptime"),
})
return rows
Prefer structured parser output when available, but store raw output with the incident record because BGP summary formats vary by platform and address family.
These actions can affect routing and should not be suggested as automatic diagnostics:
If a reset is approved, prefer the least disruptive soft or route-refresh option supported by the platform and document exactly why it is safe.
Active always means the remote side is down.received-routes output as proof that no routes arrived.cisco-ios-patternsnetwork-config-validationnetwork-interface-health