Question

Difficulty: MediumTroubleshooting IP Addressing and DHCP Services

A network administrator is troubleshooting an issue where a newly connected Linux host receives an IP address via DHCP but cannot communicate with hosts on external subnets. Arrange the following diagnostic and troubleshooting steps into the correct chronological order according to standard Network+ troubleshooting methodology.

  1. 1Verify physical layer link status and interface activity LED indicators on the network adapter.
  2. 2Examine the IP configuration and routing table using `ip addr` and `ip route` to confirm the default gateway IP address.
  3. 3Execute an ICMP ping to the local default gateway IP address.
  4. 4Execute an ICMP ping to a known public remote IP address such as 8.8.8.8.
  5. 5Perform a domain name resolution query using `dig` or `nslookup` against an external hostname.

Answer

The correct troubleshooting sequence begins with verifying physical link status, inspecting the local IP address and routing table for the default gateway, pinging the local default gateway, pinging a remote public IP address, and finally testing DNS domain name resolution.
Following standard CompTIA troubleshooting methodology, network diagnostics proceed logically from Layer 1 to higher layers: verify physical link integrity, inspect local IP and routing parameters (default gateway), test local subnet gateway reachability via ICMP, test external path routing via IP ping, and finally test higher-layer application services like DNS name resolution.

Step-by-Step Solution

1
Check physical layer connectivity
Confirmed physical link integrity
Lower-layer physical connectivity issues must be ruled out before inspecting protocol-layer configuration.
2
Inspect IP configuration and default gateway entry
Identified configured IP address, subnet mask, and default gateway router address
Determines if the DHCP server supplied valid addressing details including the default gateway route.
3
Ping the local default gateway
Verified local subnet Layer 3 communication
Tests basic local packet forwarding and ARP resolution to the local router interface.
4
Ping a remote external IP address
Verified remote IP routing past the local gateway
Isolates network layer routing path issues from higher-level application/DNS issues.
5
Test DNS resolution with dig or nslookup
Verified full end-to-end service availability
Ensures domain names resolve to IP addresses after underlying IP reachability is established.

Key Concept

Standardized bottom-up IP addressing and DHCP service troubleshooting sequence
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