S26-Troubleshooting Network Services

Question 1

Which Layer is concerned with MAC addresses?

Answer 1

Layer 2

Question 2

What 2 parts Comprise a MAC address?

Answer 2

48 bit hexadecimal number:
- First 24 bits manufacturer ID (OUI)
- last 24 bits unique device DI

Question 3

Logical Domain Manger

Answer 3

Listens to multicast messages on a network and keeps track of the MAC addresses being used

Question 4

What things can you do to detect and resolve duplicate MAC addresses?

Answer 4

• setup Logical Domain Manager
• use a Protocol Analyzer eg. Wireshark
• Enable port security on Switches

Question 5

Duplicate IP addresses/ IP address Conflict

Answer 5

Devices on the same network have identical IP addresses

Question 6

What is typically the cause of IP Conflicts?

Answer 6

• Static IP address config error
• DHCP server issue
• Rogue DHCP server

Question 7

DHCP

Answer 7

Network management protocol used to automatically assign IP information

Question 8

Rogue DHCP

Answer 8

Unauthorized DHCP server on a network

Question 9

In what ways can you counter a rogue DHCP

Answer 9

• Configure DHCP snooping
• Port security on switch ports
• use Intrusion Detection system

Question 10

DHCP Scope Exhaustion

Answer 10

Occurs when the DHCP server runs out of valid IPs to assign

Question 11

What is the default Lease Time for most DHCP servers?

Answer 11

86400 sec (1 Day)

Question 12

T/F Longer lease times can lead to Scope exhaustion

Answer 12

True

Question 13

Multicast Flooding

Answer 13

multicast traffic is unnecessarily duplicated and sent to every port on a switch or router, wasting network resources and causing congestion

Question 14

What can you do to prevent Multicast floods?

Answer 14

Configure the switch to block unknown multicast packets

Question 15

Asymmetrical Routing

Answer 15

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

Question 16

Missing Routes

Answer 16

Router cannot reach a destination due to a missing route in the routing table

Question 17

Switching Loop

Answer 17

more than one path between two endpoints, causing traffic to circulate endlessly

Question 18

Routing Loop

Answer 18

network packets get trapped in a cycle between routers, continuously passing through them without reaching their intended destination

Question 19

How do you prevent a switching Loop?

Answer 19

Enable STP (Spanning tree Protocol)

Question 20

Split Horizon

Answer 20

Routing Config that stops a route from being advertised back in the direction it came from
- helps to prevent routing loops

Question 21

Route Poisoning

Answer 21

Increasing a router’s metric to a high value after detecting one of its connected routes failed

Question 22

Hold-Down Timer

Answer 22

Prevents bad routes from being restored and passed on

Question 23

What is the default Hold-Down period?

Answer 23

180 seconds (3 mins)

Question 24

Host-Based Firewall

Answer 24

Software firewall that runs on, and protects an individual device on the network

Question 25

Network-Based Firewall

Answer 25

firewall deployed on the network that monitors and filters ingress and egress network traffic using rule sets

Question 26

What causes connectivity issues in regards to firewalls?

Answer 26

Either traffic is not going THROUGH or not going TO the firewall properly

Question 27

What should you always check when dealing with firewall issues

Answer 27

check the Access control list (ACL) and ensure that there are no typos an that the rules are in the right sequence

Question 28

What 4 key pieces of information does a network client need to communicate on the network?

Answer 28

IP Address Subnet Mask Default Gateway IP DNS server IP

Question 29

What can you do if a client can connect to the DNS server but there is still a DNS issue?

Answer 29

- Flush the DNS cache - Change the DNS configuration

Question 30

What things to check when troubleshooting the DNS server

Answer 30

- Verify A & CNAME records were properly created -

Question 31

What command do you use to verify DNS records?

Answer 31

nslookup

Question 32

Common issues with A and CNAME records

Answer 32

A records: - ensure the domain name and IP address is entered correctly CNAME Records: - ensure the source and destination domain names are spelled properly

Question 33

DNS Latency

Answer 33

Delay that occurs whenever users request a particular domain name

Question 34

What can you do to reduce DNS latency

Answer 34

Use DNS servers that are closer to your users eg. one you host yourself or one provided by your ISP

Question 35

NTP

Answer 35

Allows synchronization of system clocks across a network

Question 36

General issues with NTp

Answer 36

NTP packets not received NTP packets Not processed NTP packets have errors or are lost