Troubleshooting Network Issues

Question 1

Startup Configuration

Answer 1

Stored in NVRAM and contains the commands needed to initially configure a router

Question 2

VLAN Assignment/Tagging

Answer 2

Practice of segmenting an IT organization’s network, separating users into respective network sections

VLAN Membership Policy Server (VMPS), client, server, and database

Question 3

Network Performance Baseline

Answer 3

Defines the normal working conditions of an enterprise network infrastructure

Question 4

Collision

Answer 4

Occurs when two hosts on the network transmit at the same time which
causes the signals to combine on the network medium

Collisions occur in both wired and wireless networks

Question 5

Collision Domain

Answer 5

Network segment where simultaneous data transmissions collide with one another

Use any Layer 2 device to break apart collision domains

Turn off auto-negotiation
Hardcode lower speed
Change to half-duplex

Question 6

Broadcast Storm

Answer 6

Occurs when a network system is overwhelmed by continuous multicast or broadcast traffic

Layer 2: FF:FF:FF:FF:FF:FF
Layer 3: 255.255.255.255

Question 7

Broadcast Domain

Answer 7

A logical division of computer network where all nodes can reach each other by broadcast at the data link layer

Layer 2 devices will not break up a broadcast domain

Too large singular broadcast domain: Use a router to break up subnets into separate broadcast domains

Loops are created in the switching environment:
Enable Bridge Protocol Data Units (BPDU) on managed switches
Enforce a maximum number of MAC addresses per port
Break up large broadcast domains into smaller domains using routers and Layer 3 switches

Question 8

Routing: Multicast Flooding

Answer 8

No specific host is associated with the multicast MAC address in the CAM table of the switch

Question 9

Routing: Asymmetrical Routing

Answer 9

Network packets leave via one path and return via a different path

Routing issues cause issues with dropped packet flows

Question 10

Loops: Switching/Bridge Loop

Answer 10

Switching loops are usually an issue with how STP is configured

Question 11

Loops: Routing Loop

Answer 11

Formed when an error occurs in the operation of the routing algorithm and creates a circular route amongst a group of network devices

Routing loops are caused by logical Layer 3 circular connections that may
exist in a routing table

Question 12

Loops: Split Horizon

Answer 12

Routing configuration that stops a route from being advertised back in the direction from which it came

ip split-horizon
no ip split-horizon

Question 13

Loops: Route Poisoning

Answer 13

Increasing a router’s metric to an infinitely high number after detecting one of its connected routes has failed

Question 14

Loops: Hold-Down Timer

Answer 14

Prevents bad routes from being restored and passed to other routers by
accident

Hold-down period: 180 seconds (3 minutes)
Statically-created routes are given a metric of 1 by default

Question 15

DNS Problems

Answer 15

High CPU usage increases latency, jitter, and packet loss

Use a cable tester for twisted pair connections or a fiber light meter for fiber
optic connections

Question 16

Low Optical Link Budget

Answer 16

Optical Link Budget is a calculation that considers all the anticipated losses along the length of a fiber optic connection

Reduced transmission
Slow connection speeds
Connection downtime

0.25 dB per km for a standard fiber optic cable
Calculate optical link budget by using power budget minus the loss over the fiber cable’s distance