Pyats Routing

Routing Protocol Analysis

Routing Table Analysis

Always start here. The routing table is the source of truth for forwarding decisions.

Full Routing Table

PYATS_TESTBED_PATH=$PYATS_TESTBED_PATH python3 $MCP_CALL "${PYATS_PYTHON:-python3} -u $PYATS_MCP_SCRIPT" pyats_run_show_command '{"device_name":"R1","command":"show ip route"}'

Per-Protocol Routes

# OSPF routes only
PYATS_TESTBED_PATH=$PYATS_TESTBED_PATH python3 $MCP_CALL "${PYATS_PYTHON:-python3} -u $PYATS_MCP_SCRIPT" pyats_run_show_command '{"device_name":"R1","command":"show ip route ospf"}'

# BGP routes only
PYATS_TESTBED_PATH=$PYATS_TESTBED_PATH python3 $MCP_CALL "${PYATS_PYTHON:-python3} -u $PYATS_MCP_SCRIPT" pyats_run_show_command '{"device_name":"R1","command":"show ip route bgp"}'

# Connected and static
PYATS_TESTBED_PATH=$PYATS_TESTBED_PATH python3 $MCP_CALL "${PYATS_PYTHON:-python3} -u $PYATS_MCP_SCRIPT" pyats_run_show_command '{"device_name":"R1","command":"show ip route connected"}'

PYATS_TESTBED_PATH=$PYATS_TESTBED_PATH python3 $MCP_CALL "${PYATS_PYTHON:-python3} -u $PYATS_MCP_SCRIPT" pyats_run_show_command '{"device_name":"R1","command":"show ip route static"}'

VRF Routes

PYATS_TESTBED_PATH=$PYATS_TESTBED_PATH python3 $MCP_CALL "${PYATS_PYTHON:-python3} -u $PYATS_MCP_SCRIPT" pyats_run_show_command '{"device_name":"R1","command":"show ip route vrf MGMT"}'

Analysis checklist:

• Route source codes: C (connected), S (static), O (OSPF), O IA (OSPF inter-area), O E1/E2 (OSPF external), B (BGP), D (EIGRP), D EX (EIGRP external)
• Administrative distance and metric for each route
• Next-hop reachability — is the next-hop IP actually reachable?
• Recursive lookups — routes pointing to next-hops resolved through other routes
• Equal-cost multipath (ECMP) — multiple next-hops for the same prefix
• Default route presence and source
• Unexpected route absence — if a prefix should be there but is not

OSPF Deep Dive

OSPF Process Overview

PYATS_TESTBED_PATH=$PYATS_TESTBED_PATH python3 $MCP_CALL "${PYATS_PYTHON:-python3} -u $PYATS_MCP_SCRIPT" pyats_run_show_command '{"device_name":"R1","command":"show ip ospf"}'

Check: Router ID, areas configured, SPF run count (high = instability), reference bandwidth, stub/NSSA config, authentication.

OSPF Neighbors

PYATS_TESTBED_PATH=$PYATS_TESTBED_PATH python3 $MCP_CALL "${PYATS_PYTHON:-python3} -u $PYATS_MCP_SCRIPT" pyats_run_show_command '{"device_name":"R1","command":"show ip ospf neighbor"}'

Neighbor state analysis:

• FULL — Healthy, full adjacency
• FULL/DR or FULL/BDR — Normal on broadcast/NBMA networks
• FULL/DROTHER — Normal on broadcast/NBMA (non-DR/BDR)
• 2WAY/DROTHER — Normal, two DROTHERs don't form full adjacency
• INIT — One-way communication only → check MTU, ACLs, authentication
• EXSTART/EXCHANGE — Stuck in database exchange → MTU mismatch (most common), OSPF area mismatch, authentication
• LOADING — Stuck loading LSAs → database corruption, memory issues
• DOWN — No hello packets → interface down, ACL blocking, hello/dead timer mismatch

Common OSPF problems and their symptoms:

OSPF Interfaces

PYATS_TESTBED_PATH=$PYATS_TESTBED_PATH python3 $MCP_CALL "${PYATS_PYTHON:-python3} -u $PYATS_MCP_SCRIPT" pyats_run_show_command '{"device_name":"R1","command":"show ip ospf interface"}'

Check per interface: Area assignment, network type (broadcast/point-to-point/NBMA), cost, hello/dead timers, DR/BDR election, authentication type, passive status.

OSPF Database (LSDB)

PYATS_TESTBED_PATH=$PYATS_TESTBED_PATH python3 $MCP_CALL "${PYATS_PYTHON:-python3} -u $PYATS_MCP_SCRIPT" pyats_run_show_command '{"device_name":"R1","command":"show ip ospf database"}'

LSA types to understand:

• Type 1 (Router LSA) — Every router generates one per area
• Type 2 (Network LSA) — DR generates on broadcast/NBMA segments
• Type 3 (Summary LSA) — ABR advertises between areas
• Type 4 (ASBR Summary) — ABR advertises ASBR reachability
• Type 5 (External LSA) — ASBR redistributes external routes
• Type 7 (NSSA External) — External routes in NSSA areas (converted to Type 5 at ABR)

Red flags in LSDB:

• Rapidly incrementing sequence numbers → LSA flooding loop
• Type 5 LSAs in stub area → misconfiguration
• Missing Type 3 LSAs for expected inter-area prefixes → ABR filtering or area mismatch
• Duplicate Router IDs → same RID on two routers

BGP Deep Dive

BGP Summary

PYATS_TESTBED_PATH=$PYATS_TESTBED_PATH python3 $MCP_CALL "${PYATS_PYTHON:-python3} -u $PYATS_MCP_SCRIPT" pyats_run_show_command '{"device_name":"R1","command":"show ip bgp summary"}'

Check: Local AS, router ID, table version, total paths/best paths, per-neighbor state.

Neighbor state column meaning:

• Number (e.g., 5) → Established, number = received prefixes
• Idle → Not configured correctly, or administratively shut
• Idle (Admin) → neighbor shutdown configured
• Active → TCP connection failing → check reachability, TTL, ACLs
• Connect → TCP SYN sent, no response
• OpenSent → TCP connected, waiting for OPEN reply
• OpenConfirm → OPEN received, waiting for KEEPALIVE
• Established → Healthy

BGP Neighbors Detail

PYATS_TESTBED_PATH=$PYATS_TESTBED_PATH python3 $MCP_CALL "${PYATS_PYTHON:-python3} -u $PYATS_MCP_SCRIPT" pyats_run_show_command '{"device_name":"R1","command":"show ip bgp neighbors"}'

Deep analysis per neighbor:

• BGP state, uptime, last reset reason
• Messages sent/received (OPEN, UPDATE, KEEPALIVE, NOTIFICATION)
• Hold time and keepalive interval
• Address families negotiated
• Route-map/filter-list/prefix-list applied (inbound/outbound)
• Next-hop-self, soft-reconfiguration, route-reflector-client status
• Notification messages — decode the error code/subcode

Common BGP problems: