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Lab 60: Basic Static IPv4 Setup & Connectivity Test

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Configure a static IPv4 address using ip tooling, bring the interface online, and add a default route. Validate end-to-end connectivity with a controlled ping test.

network core troubleshooting

Scenario

You have been asked to configure enp1s0 with a static IPv4 address for a staging subnet and confirm the host can reach the network beyond its default gateway. Target configuration: 192.168.50.10/24 with default gateway 192.168.50.1.

Operator context

This workflow is common during provisioning, temporary migrations, and controlled connectivity testing. You are making direct, explicit changes using ip, then verifying the outcome immediately.

Objective

  • Assign 192.168.50.10/24 to enp1s0.
  • Bring enp1s0 to an UP state.
  • Add a default route via 192.168.50.1.
  • Verify external reachability with a single ICMP echo.

Concepts

  • Addressing and link state are separate: you can configure an IP on a DOWN interface, but it will not pass traffic.
  • A default route is required for traffic destined outside your directly connected subnets.
  • ip changes made this way are not persistent across reboot unless you also configure your network manager.
  • A single-packet ping is a fast validation step that reduces noise while confirming reachability.
  • If external ping fails, verify gateway reachability first, then routing, then firewall policy.

Walkthrough

Step 1 : Assign 192.168.50.10/24 to enp1s0.
Command 
ip addr add 192.168.50.10/24 dev enp1s0

This adds the address to the interface. If the same address already exists, the command will fail, which is useful feedback during repeatable testing. 

# Verify address:
ip -br addr show dev enp1s0
# Expected to include:
# enp1s0 ... 192.168.50.10/24
Step 2 : Bring enp1s0 up.
Command 
ip link set enp1s0 up

The interface must be UP to send and receive traffic. Validate link state before diagnosing routing or reachability. 

# Confirm link state:
ip -br link show dev enp1s0
# Expected:
# enp1s0 UP ...
Step 3 : Add the default route via 192.168.50.1.
Command 
ip route add default via 192.168.50.1 dev enp1s0

The default route determines where traffic goes when no more specific route matches. Without it, external pings may fail even when local addressing is correct. 

# Verify routing table:
ip route
# Expected to include:
# default via 192.168.50.1 dev enp1s0
Step 4 : Confirm the gateway is reachable.
Command 
ping -c 1 192.168.50.1

This is the most important intermediate validation step. If you cannot reach the gateway, external reachability will fail, and you should focus on link, addressing, VLAN, or switchport state. 

1 packets transmitted, 1 received, 0% packet loss
Step 5 : Verify external reachability with one ICMP echo.
Command 
ping -c 1 8.8.8.8

This confirms basic reachability beyond the local subnet. Using an IP avoids DNS variables and isolates routing/forwarding. 

1 packets transmitted, 1 received, 0% packet loss

Breakpoints

RTNETLINK answers: File exists

If adding the address or default route fails with “File exists,” list current config, then remove the conflicting entry before re-adding the target configuration.

Interface stays DOWN

If ip link set shows UP but traffic still fails, confirm physical link or virtual NIC connection and check for carrier state using ip -br link.

Gateway unreachable

If ping 192.168.50.1 fails, verify subnet correctness, VLAN placement, and switchport state. Do not troubleshoot external routing until the gateway is reachable.

Cleanup checklist

  • Remove the static IP from enp1s0.
  • Remove the default route you added (if it was not pre-existing).
Commands 
ip addr del 192.168.50.10/24 dev enp1s0
ip route del default via 192.168.50.1 dev enp1s0

Reference

  • ip addr add <ip>/<prefix> dev <iface> : Add an address to an interface.
  • ip addr del <ip>/<prefix> dev <iface> : Remove an address from an interface.
  • ip link set <iface> up : Bring an interface up.
  • ip route add default via <gateway> dev <iface> : Add a default route.
  • ip route del default via <gateway> dev <iface> : Remove a default route.
  • ip -br addr show dev <iface> : Brief address view for an interface.
    • -br: brief output
  • ip -br link show dev <iface> : Brief link-state view for an interface.
    • -br: brief output
  • ping -c 1 <ip> : Send one ICMP echo request.
    • -c 1: exactly one packet