Bgp Analysis
by @vahagn-madatyan
BGP protocol analysis with peer state diagnosis, path selection verification, route filtering validation, and convergence assessment. Multi-vendor coverage f...
Session Flapping
Peer cycles between Established and Idle/Active repeatedly. Common causes:
unstable underlying transport (IGP flap, link errors), aggressive hold timers
on congested control planes, or MTU issues on the path causing fragmented
keepalives to be dropped. Check last reset reason and correlate with interface
or IGP events at the same timestamps.
Route Oscillation
The same prefix alternates between two or more paths. Caused by inconsistent
MED comparison across route reflectors, or deterministic-MED not enabled when
multiple exit points exist to the same neighbor AS. Enable always-compare-med
and deterministic-med to stabilize.
Memory Pressure from Full Table
Full Internet table (~950K IPv4 prefixes) requires 1β2 GB of RIB memory depending on path diversity. Symptoms: slow convergence, peer resets during table reload. Mitigate with soft-reconfiguration inbound (trades memory for stability) or ORF (Outbound Route Filtering) to reduce inbound load.
Community Stripping
Routes arrive without expected communities. Check each transit AS in the path β many providers strip non-standard communities by default. Use large communities (RFC 8092) for end-to-end propagation across providers that strip standard communities.
JunOS Default Export Policy
JunOS sends no routes to a peer without an explicit export policy. If a peer shows Established with zero prefixes sent, add an export policy. This is the most common JunOS-specific BGP issue and does not occur on Cisco or EOS.
clawhub install bgp-analysis