13 - Implementing Pt to Pt WANS

Question 1

What is CPE?

Answer 1

Customer Premise Equipment

Question 2

What does CSU/DSU stand for?

Answer 2

Channel Service Unit / Data Service Unit

Question 3

What does a CSU/DSU do?

Answer 3

Provides clocking on the line controlling the speed and timing that the router can send each bit over the line

Question 4

What is the bit rate for a DS0?

Answer 4

64 Kbps

Question 5

What is another name for DS1?

Answer 5

T1

Question 6

What is the bit rate for a T1?

Answer 6

1.544 Mbps

Question 7

What multiples make up a Fractional T1?

Answer 7

Multiples of 64 Kbps

Question 8

What multiples make up a Fractional T3?

Answer 8

Multiples of 1.536 Mbps

Question 9

What is the bit rate for a T3?

Answer 9

44.736 Mbps

Question 10

What does DCE stand for?

Answer 10

Data Circuit-terminating Equipment

Question 11

What does the DCE funtion do?

Answer 11

Controls the speed of the router’s serial interface

Question 12

What does DTE stand for?

Answer 12

Data Terminal Equipment

Question 13

What does the DTE do?

Answer 13

DTE is the router that is controlled by the DCE

Question 14

How is Cisco’s HDLC protocol different that ISO’s HDLC?

Answer 14

Cisco adds a Type field that allows the serial line to support multiple types of network layer packets

Question 15

What are the 6 fields in a Cisco HDLC frame?

Answer 15

• Flag
• Address
• Control
• Type
• Data
• FCS

Question 16

What are 2 ways to enable HDLC encapsulation on an interface?

Answer 16

• ‘no encapsulation’ cmd to return to default HDLC or
• encapsulation HDLC

Question 17

What 2 ‘show’ commands that confirm a serial link has been successfully installed?

Answer 17

• show controllers s0/0/0
• show interfaces s0/0/0

Question 18

What 5 things does PPP provide?

Answer 18

• defines a header and trailer
• supports both synchronous and asynchronous
• Protocol Type field allowing multiple layer 3 protocols
• Built-in authentication tools
• control protocols for each higher-layer protocol riding over PPP

Question 19

In PPP frame what does the Type field do?

Answer 19

Identifies which L3 protocol is in the frame

Question 20

in PPP what are the 2 categories of Control Protocols?

Answer 20

• Link Control Protocols (LCP)
• Network Control Protocols (NCP)

Question 21

What are 3 examples of NCPs?

Answer 21

• IPCP
• IPv6CP
• CDPCP

Question 22

What are 4 LCPs?

Answer 22

• Looped Link Detection
• Error Detection
• Multilink Support
• Authentication

Question 23

In PPP what are the 2 Authentication protocols?

Answer 23

• PAP
• CHAP

Question 24

How does the PAP authentication process work?

Answer 24

• The router wanting to be authenticated - R2 - starts the conversation
• R2 tells R1 username and password in clear text
• R1 Acknowledges auth successful

Question 25

How does the CHAP process work?

Answer 25

* The router doing the authenticating - R1 - initiates * R1 sends challenge that includes a Random Number to R2 * R2 replies with a MD5 Hash created from the Random Number and the Password * R1 acknowledges auth successful

Question 26

In PPP CHAP what does the Challenging router do if authentication fails?

Answer 26

Leaves interface in Up/Down state

Question 27

What kind of Hash does PPP CHAP use?

Answer 27

MD5

Question 28

What is the command to enable PPP on an interface?

Answer 28

encapsulation ppp

Question 29

What show command verifies that PPP has been enabled?

Answer 29

* show interfaces s0/0/0 * will show encapsulation ppp * also LCP Open * also Open: IPCP, CDPCP

Question 30

What configuration steps are needed on router1 to configure CHAP?

Answer 30

* encapsulation ppp * hostname router1 * username router2 password letmein * interface s0/0/0 * ppp authentication chap

Question 31

What configuration steps are needed on router2 to configure CHAP?

Answer 31

* encapsulation ppp * hostname router2 * username router1 password letmein * interface s0/0/0 * ppp authentication chap

Question 32

When configuring PPP CHAP which two parameters need to match?

Answer 32

* username on local router must match hostname on remote router * passwords must be the same

Question 33

What show command confirms authentication succeeded?

Answer 33

* show ppp all * should show '+' for every protocol that succeeded

Question 34

When configuring PPP PAP which parameters need to match?

Answer 34

* interface s0/0 * ppp pap sent-username r1 password test * * must match username r1 password test on remote router

Question 35

What 'show' command will show if PAP authentication worked?

Answer 35

\* show ppp all \* should show '+' for every protocol that succeeded

Question 36

What configuration steps are needed to configure PAP?

Answer 36

\* interface subcommands \* encapsulation ppp \* ppp authentication pap \* ppp pap sent-username r1 password test \* then on remote router username r1 password test

Question 37

What command will tell a router to try CHAP first and if that doesn't succeed try PAP

Answer 37

\* ppp authentication chap pap

Question 38

Which layer does MLPPP load balance at?

Answer 38

Layer 2

Question 39

Which 2 'show' commands verify MLPPP is working?

Answer 39

\* show interfaces multilink 1 \* show ppp multilink

Question 40

What does an interface state of down/down indicate?

Answer 40

a problem at layer 1

Question 41

What does an interface state of up/down indicate?

Answer 41

a problem at layer 2

Question 42

What does an interface state of up/up indicate?

Answer 42

layer 3 is working

Question 43

What are some possible causes of interfaces in down/down state?

Answer 43

\* cable unplugged \* bad cable \* broken CSU \* problem at telco

Question 44

What could be the problem when interfaces are up/down flapping on both ends?

Answer 44

Mismatched encapsulation commands

Question 45

What could be the problem if one side is up/down and the other side is up/up?

Answer 45

Keepalives disabled on the up/up side

Question 46

What could be the problem when interfaces are up/down on both ends but NO Flapping?

Answer 46

PAP or CHAP Authentication Failure

Question 47

How often are keepalives sent to the remote router by default?

Answer 47

once every 10 seconds

Question 48

What debug command will help diagnose a PPP Authentication Failure?

Answer 48

debug ppp authentication