21 - Troubleshooting IPv4 Routing

Question 1

What cmd do you use to disable DNS lookups on a router?

Answer 1

no ip domain-lookup

Question 2

What are the 4 troubleshooting steps to take for a DHCP problem?

Answer 2

• correctly configured ‘ip helper-address’ on the LAN interface * check connectivity btw DHCP relay agent and DHCP server * check connectivity btw the Client and the DHCP relay agent (router) * troubleshoot incorrect DHCP server configuration

Question 3

5 reasons that a router LAN interface may fail to reach an UP/UP state?

Answer 3

• Speed mismatch (down/down) * interface shut down on router (admin down) * switch interface admined down (down/down) * Err-disabled interface on switch (down/down) * no cable / bad cable (down/down)

Question 4

What 4 things can create over-lapping subnets?

Answer 4

• autosummarization * manual route summarization * static routes * incorrectly designed subnetting plans

Question 5

When more than 1 route matches a destination address how does the router decide which route to follow?

Answer 5

• the route with the longest prefix-length MASK

Question 6

What ‘show’ cmd will show the next hop the router will send the packet to?

Answer 6

show ip route (destination)