sands-lab/nika/ospf-fault-skill

OSPF And FRR Faults

What These Faults Mean

• frr_service_down: the routing daemon stack is not running, even if config files still look valid.
• ospf_neighbor_missing: the router is not correctly participating in OSPF adjacency or route origination, often because expected network statements are missing.
• ospf_area_misconfiguration: a specific adjacency-carrying link is placed in the wrong OSPF area relative to peer or topology expectations.
• ospf_acl_block: router firewall policy blocks OSPF packets even though interfaces and config may look otherwise healthy.

Leading Signals

• One router or one routed segment loses paths while interfaces remain present.
• show ip ospf neighbor and show running-config prove adjacency and area state directly.
• FRR process checks separate dead control plane from bad config.

Exact Calls

• exec_shell(host_name="<router>", command="ps aux | grep -E 'zebra|ospfd|watchfrr' | grep -v grep")
• exec_shell(host_name="<router>", command="vtysh -c 'show ip ospf neighbor'")
• exec_shell(host_name="<router>", command="vtysh -c 'show running-config'")
• exec_shell(host_name="<router>", command="nft list ruleset")
• frr_show_running_config(router_name="<router>")
• frr_show_ip_route(router_name="<router>")

Required Tool Usage

• FRR MCP tools use router_name, not host_name.
• If you are unsure of the FRR helper schema, use exec_shell(host_name="<router>", command="vtysh -c '...'").
• frr_show_running_config and frr_show_ip_route are secondary evidence only; they can look healthy when FRR is down.

One-Pass Coverage

• python diagnosis-methodology-skill/scripts/ospf_snapshot.py

Submit on match

When direct evidence on a router (process state, OSPF config, area assignment, or nft rule) is sufficient to identify the fault, submit. Do not chain extra probes once the family is confirmed.

Guardrails

• Do not infer ospf_area_misconfiguration from LSDB differences alone.
• You need direct config evidence for the wrong area on a specific link.
• Clean service checks do not clear silent OSPF faults on redundant topologies.
• If hosts lose DHCP renewal behind one router, keep OSPF in play.
• A clean ospf_snapshot does not clear L2 identity faults: duplicate MACs can create intermittent or status=unknown routed symptoms while FRR and routes still look healthy, so verify l2_snapshot has run before concluding no anomaly.