200-301 Router R1 Cannot Reach R3 Practice Questions

Explanation: First, the DHCP server must be properly configured on the router. Next, DHCP snooping is enabled globally on the switch to protect against rogue servers. Then, the specific client VLANs must be added to the snooping database. After that, the uplink interface to the DHCP server must be trusted to allow legitimate server responses. Finally, the ip helper-address command is placed on the client's SVI to forward DHCP broadcasts to the remote server.

Explanation: The 'ip nat outside' command must be applied to the interface facing the external network (GigabitEthernet0/0) for the router to translate return traffic. Without it, the router does not perform NAT on packets arriving on that interface, so replies from external servers are forwarded without translation back to the inside local IPs, which are not routable on the internet. The stale translations indicate that outbound translations were created but never used for return traffic, confirming the missing outside interface command.

Explanation: The router's G0/0/0 interface is up/up, but the IPv6 address is not in the expected EUI-64 format. This indicates that the 'ipv6 address' command was likely omitted entirely, because if it were simply misconfigured (e.g., without the `eui-64` keyword), the router would still automatically generate a link-local address, and hosts would be able to reach it. Since hosts cannot reach the link-local address, IPv6 is not enabled on the interface at all. The correct configuration requires the `ipv6 address` command with the appropriate prefix and the `eui-64` keyword.

Explanation: The default route uses a next-hop IP (10.10.10.2) and will only be installed in the routing table if that next-hop is reachable. Since the router’s routing table shows no default route, the most likely cause is that the next-hop 10.10.10.2 is unreachable, preventing the static route from being used. This explains why traffic fails despite the configuration.

Explanation: The traffic uses the OSPF route because it is the more specific match. In practical terms, the router evaluates destination-prefix specificity before comparing route source preference. The static route points to a broader /24, while the OSPF entry points to a narrower /26 that still contains the destination. Because longest-prefix match comes first, the /26 route wins. This is a good reminder that static routes do not automatically beat dynamic routes when the prefixes are different. Specificity matters first, then source preference only when the prefix length is the same.