N10-009 Question 140
Single answerStatic routingA small branch office has a single router connected to the headquarters router over a point-to-point WAN link. The branch LAN is 192.168.50.0/24, and the headquarters LAN is 10.20.0.0/16. Users at the branch can reach local resources, but they cannot access servers at headquarters. The WAN link is up, and the branch router can successfully ping the headquarters router's WAN interface at 172.16.1.1. The branch router's routing table contains only directly connected networks. Which action should the network administrator take on the branch router to restore connectivity to the headquarters LAN?
- A
Configure a static route to 10.20.0.0/16 using 172.16.1.1 as the next-hop address
- B
Configure a default gateway on the branch router pointing to 192.168.50.1
- C
Enable DHCP relay on the branch router for the 10.20.0.0/16 network
- D
Configure a static route to 172.16.1.1/32 using 10.20.0.1 as the next-hop address
Show answer and explanation
Correct answer: A
Explanation
This scenario tests practical static routing. Because the branch router's table contains only directly connected networks, it does not know how to forward traffic destined for the headquarters LAN 10.20.0.0/16. The successful ping to 172.16.1.1 confirms the WAN path to the neighboring router is working, so the missing piece is a route for the remote LAN. The correct fix is to configure a static route for the destination network via the headquarters router's WAN next hop. This aligns with standard routing behavior described by major networking vendors such as Cisco and Juniper: static routes define a destination prefix and a next-hop IP address or exit interface so the router can forward traffic toward non-local networks. Best practice in small or stable environments is to use static routing when the path is simple and changes infrequently.
- A. Correct.
Correct. The branch router already knows its directly connected networks, but it has no route to the remote headquarters LAN 10.20.0.0/16. Adding a static route for that destination network and pointing it to the reachable next-hop WAN address 172.16.1.1 allows traffic for headquarters to be forwarded correctly across the WAN link.
- B. Incorrect.
Incorrect. Routers use routing tables, not a host-style default gateway configuration in this context. Also, 192.168.50.1 is typically a local LAN interface address and would not help the router reach a remote network. The issue is the absence of a route to 10.20.0.0/16, not the lack of a local gateway.
- C. Incorrect.
Incorrect. DHCP relay is used to forward DHCP broadcast requests between subnets so clients can obtain IP configuration from a remote DHCP server. It does not create Layer 3 reachability to a remote network and would not solve a missing route to headquarters resources.
- D. Incorrect.
Incorrect. A host route to the headquarters router's WAN IP is unnecessary because the branch router can already ping 172.16.1.1, which indicates reachability to that address already exists through a directly connected or known WAN network. Pointing that route to 10.20.0.1 is also illogical because that is an address in the very remote network the router cannot currently reach.