WAN troubleshooting

Question 1

if you have cable or DSL, what do you need to check first when troubleshooting loss of internet connectibity?

Answer 1

interface errors on the LAN ports connecting to your router

Question 2

what is the most common cause of interface errors?

Answer 2

mismatched duplex mode

Question 3

Input Queue Drops on a router tell you what?

Answer 3

that more traffic is being delivered to the router than it can process

Question 4

Output Queue Drops indicate what?

Answer 4

that packets were dropped due to interface congestion.

Question 5

Cabling problems, hardware issues or duplex mismatches can be indicated by a high number of what on the interface?

Answer 5

High Input Errors

Question 6

What interface indicator equals the total number of frames that the port tried to transmit when an issue like a collision occurred.

Answer 6

Output Errors

Question 7

On a serial interface of a router, what do you check first when troubleshooting connectivity issues?

Answer 7

Clocking

Question 8

What is the term given to the issue where multiple PVCs coming into a single WAN interface and this can cause routes being dropped because the routing protocol thinks that it’s receiving routes on the same interface they were being sent out of?

Answer 8

Split Horizon

Question 9

How can Split Horizon be avoided?

Answer 9

By creating sub-interfaces

Question 10

When troubleshooting router configs, what’s the first thing you should check?

Answer 10

The default route

Question 11

What two security policy related issues can affect internet connectivity?

Answer 11

1) Blocking ports

2) slow-bandwidth due to enforced fair access policy