XK0-004 · Question #387
An administrator recently installed a second NIC in a server to interact with machines in an isolated enclave. However, the networking on the server has not worked since it was installed. The administ
The correct answer is A. Add a new route for each device in the isolated enclave. Adding a second NIC without defining routes for the isolated enclave leaves the kernel without a forwarding path to those hosts, breaking connectivity. Adding explicit routes resolves the routing gap.
Question
An administrator recently installed a second NIC in a server to interact with machines in an isolated enclave. However, the networking on the server has not worked since it was installed. The administrator reviews the following output:
Which of the following should be the FIRST action to remediate the issue?
Exhibit
Options
- AAdd a new route for each device in the isolated enclave
- BSet the ipv4.never-default attribute to yes for the new interface, enp0s4
- CChange DEFROUTE to no for the new interface and restart the networking
- DRestart the firewall to ensure traffic is handed appropriately
How the community answered
(54 responses)- A43% (23)
- B17% (9)
- C33% (18)
- D7% (4)
Why each option
Adding a second NIC without defining routes for the isolated enclave leaves the kernel without a forwarding path to those hosts, breaking connectivity. Adding explicit routes resolves the routing gap.
When the second NIC was installed, the routing table gained a new interface but no routes for the isolated enclave's address space were created. Adding a route for each device in the enclave tells the kernel to forward traffic destined for those hosts via the correct interface, restoring reachability. Without these entries, packets have no path and are either dropped or incorrectly sent through the default gateway.
Setting ipv4.never-default to yes on enp0s4 prevents the new interface from overriding the default gateway but does not create routes to reach the isolated enclave hosts.
Changing DEFROUTE=no and restarting networking also avoids a default route conflict but still does not add the specific routes needed to reach devices in the enclave.
Restarting the firewall does not modify the routing table and would not resolve an issue caused by missing routes or interface configuration.
Concept tested: Static route configuration for isolated network segments
Source: https://access.redhat.com/documentation/en-us/red_hat_enterprise_linux/9/html/configuring_and_managing_networking/configuring-static-routes_configuring-and-managing-networking
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