📰 Dev.to · pathvector-dev

OSPF's DR/BDR election on a broadcast segment is a filter, a max(), and a tie-break — read it as three lines of Python instead of a bullet list.

OSPF's neighbor state machine reads as two separate gates in code: Hello-phase booleans decide Init/2-Way/ExStart, and database-exchange inputs decide Loading/F

Reading OSPF's Hello check as code: the five fields that must match before a neighbor relationship can even begin, and why seeing your own router ID changes eve

Fourteen sessions of BGP logic collapse into one small Python object: six pieces of state, three methods, and one three-line rhythm repeated in each of them.

Reading a BGP event dispatcher as code: why announce gates the peer, withdraw skips the gate, and peer-down is the only branch that can touch many prefixes at o

Reading BGP export refresh as code: how one Loc-RIB change turns into an advertise for one peer, a withdraw for another, and silence for a third.

In BGP, whether a route reaches Adj-RIB-In comes down to the placement of a single if. Read the session-state gate as code.

Trace a single received BGP route end to end through validation, import policy, best-path, and export — and watch nine sessions of isolated snippets turn into o

Reading BGP peer loss as code: why a single session going down triggers a set of withdrawals plus a per-prefix best-path recomputation, and why some prefixes su

Reading BGP import policy as code: the candidate that enters best-path selection is not always the one the peer sent.

RPKI tells you a route is invalid — it does not tell the router to drop it. Read the BGP policy layer as code and see why validation and policy are separate.

BGP picking a best path doesn't mean the origin AS is authorized — read RPKI origin validation as code and see why valid, invalid, and not_found are three disti