NETWORKS · ROTEAMENTO · AVANÇADO

BGP

Interdomain routing, sessions, attributes, best-path selection, policy, filtering, communities and troubleshooting.

01 · OVERVIEW

What this topic solves

Interdomain routing, sessions, attributes, best-path selection, policy, filtering, communities and troubleshooting.

Core concepts: bgp, ebgp, ibgp, asn, policy, best, path, multihoming.

02 · MENTAL MODEL

Follow state and packet path

Start with next-hop reachability, RIB/FIB and route source. Then validate protocol state, policy, metrics, attributes and convergence.

Input → classification/state → decision → table → next-hop/output → counters

03 · DESIGN

Design before configuration

Define the failure domain and expected convergence behavior.
Document addressing, identifiers, timers, MTU and policy boundaries.
Prefer explicit, observable state over assumptions.
Plan rollback and out-of-band access before risky changes.

Operational examples

Commands and verification

Command syntax varies by platform and software release. The examples below come from the existing portal content and must be validated against the target platform documentation before production use.

Política de entrada:
peer → filtro de prefixos/AS → atributos → Loc-RIB

Política de saída:
rotas elegíveis → política/export → UPDATE → peer

# Cisco IOS/IOS XE — exemplos
show ip bgp summary
show ip bgp
show ip bgp 203.0.113.0/24
show ip bgp neighbors
show ip bgp neighbors X advertised-routes
show ip route 203.0.113.0

# MikroTik RouterOS v7
/routing/bgp/session/print detail
/routing/bgp/connection/print detail
/routing/route/print where protocol=bgp
/routing/filter/rule/print detail

04 · TROUBLESHOOTING

Evidence-driven workflow

Define source, destination, time window and exact symptom.
Establish the expected healthy state and compare it with the observed state.
Inspect counters, tables, logs and packet captures before resets.
Test one hypothesis at a time and prefer reversible changes.
Repeat the original test after correction and check side effects.

05 · STANDARDS

BGP-4 / RFC 4271 and extensions

Use the current standard/RFC and the documentation for the exact software release being operated. Vendor syntax is an implementation detail; protocol behavior should be understood independently.

06 · LAB

Prove the behavior in a controlled topology

Build the smallest topology that reproduces the mechanism, capture control and data traffic, introduce one deliberate failure and diagnose it before applying the fix.

07 · CONTINUE

BGP