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INCIDENT #152 · BGP

Regional operations: The service edge stops exchanging BGP routes

Medium25 minutesPro lab

The incident

Operations collectors reach polling and trap-receiver networks over three routed transport stages. Six routed sites provide clockwise and counterclockwise transport to a separate service gateway. Direct uplink connectivity works, but remote routers no longer learn either service prefix from the service edge. Investigate monitoring transport from R1: 10.169.224.0/24 to 10.169.236.0/24 (UDP/161), and 10.169.225.0/24 to 10.169.237.0/24 (UDP/162).

Your objective

Restore both authorized service transports and return reachability, including clients and service hosts in both halves of the primary subnet. Keep R2 blocked from both service transports, keep SSH blocked to both service subnets, and preserve monitoring between R1 and R5. Do not change physical topology or addressing. These are network forwarding checks, not application-level transactions.

The network

Network topology7 devices 7 links

Regional operations: The service edge stops exchanging BGP routes — network topologyR1: West metro. R2: Northwest metro. R3: Northeast metro. R4: Southeast metro. R5: Southwest metro. R6: East metro. R7: Service gateway. R1 connects to R2. R2 connects to R3. R3 connects to R6. R6 connects to R4. R4 connects to R5. R5 connects to R1. R6 connects to R7. Connections show physical links, not service health.R1 ↔ R2 · 10.169.240.0/30R2 ↔ R3 · 10.169.241.0/30R3 ↔ R6 · 10.169.242.0/30R6 ↔ R4 · 10.169.243.0/30R4 ↔ R5 · 10.169.244.0/30R5 ↔ R1 · 10.169.245.0/30R6 ↔ R7 · 10.169.246.0/30R1West metroR1 · West metro · Starting deviceR2NorthwestmetroR2 · Northwest metroR3NortheastmetroR3 · Northeast metroR4SoutheastmetroR4 · Southeast metroR5SouthwestmetroR5 · Southwest metroR6East metroR6 · East metroR7ServicegatewayR7 · Service gateway
Physical links · Service health not shown
7 devices · Cisco IOS syntax · Simulated network

What you’ll practice

ebgppeer as validationroute exchange

Interview exercises are inspired by common industry competencies. They are not proprietary interview questions.