5.7

Question 1

What do you do if you can ping the default gateway, but not all the hosts on remote networks?

Answer 1

Suspect Routing Issue -> Routing Table

Question 2

What problem does traceroute solve?

Answer 2

traceroute: ID where path is failing

Question 3

What problem does “route” or “show route” solve?

Answer 3

Routing table troubleshooting

Question 4

What problem does “show ip route w.x.y.z” solve?

Answer 4

Inspect a routing table for missing route

Question 5

What happens if a router fails to communicate with other routers?

Answer 5

Missing routing protocol updates and missing routes.
Might not know the topology and send packets to wrong routers.

Question 6

What should you check if there is no entry for 0.0.0.0/0 on your host?

Answer 6

Check that default gateway is configured

Question 7

What should you check if the host cannot contact remote networks?

Answer 7

Check if you can ping default gateway

Question 8

What is a common cause of routing loops?

What is one symptom of routing loop?

Answer 8

Incorrect default routes

ICMP Time Exceeded error messages

Question 9

What are 3 loop prevention methods? (3)

Answer 9

1. Max Hop Count
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2. Holddown timer: Node start a timer after sending a packet. During timer, router ignores any route updates saying route is clear. Checks the packet received info to see if route really is clear or not.
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3. Split Horizon: Idea that just b/c Router 1 can talk to Router 3. Router 2 doesn’t assume it can talk to Router 3.

Question 10

How do you diagnose routing loop through “traceroute?”

Answer 10

Looking for IP addresses that appear multiple times in the output

Question 11

When should you suspect a physical cabling problem?

Answer 11

If switch port is configured to the right VLAN but the host is assign to the wrong VLAN.

Question 12

When should you use ping?

Answer 12

To test connectivity.