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INCIDENT #225 · ROUTING

Remote access: The second client subnet gets no reply

Hard25 minutesPro lab

The incident

Managed remote clients reach access-service gateways over an enterprise transit chain; unmanaged devices use a separate branch. The core has two routed branches and a cross-link before the common service handoff. Requests reach both service networks, but the second client subnet cannot receive replies. The first client subnet still works. Investigate access gateway transport from R1: 10.179.0.0/24 to 10.179.8.0/24 (TCP/443), and 10.179.1.0/24 to 10.179.9.0/24 (UDP/1194).

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 R3. Do not change physical topology or addressing. These are network forwarding checks, not application-level transactions.

The network

Network topology5 devices 6 links

Remote access: The second client subnet gets no reply — network topologyR1: Client core. R2: North transit. R3: South transit. R4: Egress core. R5: Service gateway. R1 connects to R2. R1 connects to R3. R2 connects to R4. R3 connects to R4. R2 connects to R3. R4 connects to R5. Connections show physical links, not service health.R1 ↔ R2 · 10.179.16.0/30R1 ↔ R3 · 10.179.17.0/30R2 ↔ R4 · 10.179.18.0/30R3 ↔ R4 · 10.179.19.0/30R2 ↔ R3 · 10.179.20.0/30R4 ↔ R5 · 10.179.21.0/30R1Client coreR1 · Client core · Starting deviceR2North transitR2 · North transitR3South transitR3 · South transitR4Egress coreR4 · Egress coreR5ServicegatewayR5 · Service gateway
Physical links · Service health not shown
5 devices · Cisco IOS syntax · Simulated network

What you’ll practice

return pathstatic routingbidirectional verification

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