Cisco 200-105 Exam

Why is the Branch2 network 10.10.20.0/24 unable to communicate with the Server farm1 network 10.10.10.0/24 over the GRE tunnel?

Instructions –
– Enter Cisco IOS commands on device to verify network operation and answer for multiple-choice questions.
– THIS TASK DOES NOT REQUIRE DEVICE CONFIGURATION.
– Click the device icon to gain access to the console of the router. No console or enable passwords are required.
– To access the multiple-choice questions, click the numbered boxes on the left of the top panel.
– This task has four multiple-choice questions. Be sure to answer all four questions before clicking the Next button.

Scenario –
You are implementing PPP over serial links between R1 router and branch offices. In Phase 1 you must implement and verify PPP and GRE tunnel configurations as mentioned in the topology. In Phase 2 your colleague is expected to do NAT and ISP configurations between R1 and ISP router.
Identify the issues that you encounter during PPP over serial links implementation.
Routers Branch1, Branch2, and Branch3 connect to Router R1 in the main office over serial links.
PPP multilink implementation is recommended between R1 and Branch1 routers.
The GRE tunnel is configured between R2 and Branch2 routers, and traffic between Server farm1 10.10.10.0/24 network and Branch2 LAN 10.10.20.0/24 network, is routed over GRE tunnel using static route.
You have console access on R1, R2, Branch1, Branch2, and Branch3 devices. Use only show commands to troubleshoot the issues.

Why is the Branch2 network 10.10.20.0/24 unable to communicate with the Server farm1 network 10.10.10.0/24 over the GRE tunnel?

  • A. The GRE tunnel destination is not configured on the R2 router.
  • B. The GRE tunnel destination is not configured on the Branch2 router.
  • C. The static route point to the tunnel0 interface that is misconfigured on the Branch2 router.
  • D. The static route points to the tunnel0 interface that is misconfigured on the R2 router.
Answer: Option C.
Explanation: 

The Branch2 network is communicating to the Server farm, which is connected to R2, via GRE Tunnel so we should check the GRE tunnel first to see if it is in “up/ up” state with the “show ip interface brief” command on the two routers.
On Branch2:On R2:We see interfaces Tunnel0 at two ends are “up/up” which are good so we should check for the routing part on two routers with the “show running-config” command and pay attention to the static routing of each router. On Branch2 we see:

The destination IP address for this static route is not correct. It should be 192.168.24.1 (Tunnel0s IP address of R2), not 192.168.24.10 -> Answer C is correct.
Note: You can use the “show ip route” command to check the routing configuration on each router but if the destination is not reachable (for example: we configure
“ip route 10.10.10.0 255.255.255.0 192.168.24.10” on Branch2, but if 192.168.24.10 is unknown then Branch2 router will not display this routing entry in its routing table.
Note: The IP address or configuration may be different in the exam.

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