CoreQ Academy6.2 Given a scenario, troubleshoot network issues.
Most cloud connectivity problems come down to routes, security rules, DNS or IP ranges. Work through them in order.
Network service unavailability
- Dynamic Host Configuration Protocol (DHCP)
- Instances fail to get addresses or options, often because of DHCP option sets or exhausted scopes.
- Domain Name System (DNS)
- Names do not resolve, resolve to the wrong address or private zones are not associated with the network.
- Network Time Protocol (NTP)
- Clock drift breaks TLS, Kerberos, token validation and log correlation.
- Network Address Translation (NAT)
- Private instances cannot reach the internet without a working NAT gateway and route.
- Hypertext Transfer Protocol (HTTP)
- Web services fail or return errors.
- Status codes
- 2xx success, 3xx redirect, 4xx client error (401 unauthenticated, 403 forbidden, 404 not found, 429 throttled), 5xx server error (502 bad gateway, 503 unavailable, 504 timeout).
Performance and configuration
- Latency
- Slow responses from distance, congestion or overloaded components.
- Bandwidth/throughput issues
- Links or instance network limits saturated.
- Network device misconfiguration
- Wrong firewall, load balancer or gateway settings.
- Protocol incompatibility
- Client and server do not support the same protocol versions.
- Protocol deprecations
- Old protocols (TLS 1.0/1.1, SMBv1) disabled by providers.
IP addressing issues
- Scope exhaustion
- A subnet runs out of IP addresses, so new instances or containers fail to launch.
- Network overlap
- Two networks use the same CIDR range, so peering or VPN routing cannot work.
Routing and switching issues
- Missing routes
- No route to the destination in the route table.
- Misconfigured routes
- Routes point to the wrong target, causing black holes or asymmetric routing.
- VLAN issues
- Devices on the wrong VLAN or traffic not carried between VLANs.
- Misconfigured tags
- Wrong VLAN IDs on interfaces or trunks.
- Access vs. trunk ports
- Access ports carry one VLAN untagged; trunk ports carry multiple tagged VLANs. A mismatch drops traffic.
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Original CoreQ Academy material, mapped to objective 6.2 of the publicly available CompTIA Cloud+ CV0-004 exam objectives (Exam objectives V4, document version 5.0). Not affiliated with or endorsed by CompTIA. Contains no exam questions.