WAN Flashcards
What does DCE stand for?
Data Communication Equipment
What does HDLC stand for?
High-level Data Link Control
What is a DCE cable used to connect?
With a DTE cable, used to connect two router serial ports back to back
In Frame Relay, what does LMI stand for?
Local Management Interface
What does DLCI stand for?
Data Link Connection Identifier
What encapsulation is set on a serial interface that will connect to a frame relay network?
frame-relay
Syntax to set a serial interface to frame relay encapsulation
conf t
int s1/0
encapsulation frame-relay
2 options for encapsulation frame-relay
- cisco
2. ietf
When leaving off the specific encapsulation type for the command “encapsulation frame-relay”, what is the default?
cisco
Syntax of the frame-relay map command
frame-relay map ip ip address dlci [broadcast]
Syntax to bind a dlci to an interface
frame-relay interface-dlci dlci
Command to show InArp data
show frame-relay map
What does PPP stand for?
Point to Point Protocol
What are 2 PPP control protocols?
LCP
NCP
What do NCP and LCP stand for?
Network Control Protocols
Link Control Protocol
What’s a glaring difference between NCP and LCP?
LCP is a single protocol, whereas NCP is a suite of protocols that are each specific to a Layer 3 protocol.
4 features of PPP LCP
- Loop detection
- Error detection
- Multilink support
- Authentication
What 2 types of authentication are supported by PPP?
PAP
CHAP
What do PAP and CHAP stand for?
Password Authentication Protocol
Challenge Handshake Authentication Protocol
Which PPP auth protocol sends a password in clear text?
PAP
What are the 3 steps of a successful CHAP authenticatoin?
- Authenticator sends challenge packet.
- Caller hashes password etc and sends back hashed value.
- Authenticator compares submitted value to their own hashed value, and if they match it allows the caller in.
Command to set PPP on a serial interface
conf t
int s1/0
encapsulation ppp
2 general steps to have a PPP link use PAP or CHAP
- Configure the username/password for the calling router.
2. Set the serial link to use PPP PAP
What will the state of a serial link be if PPP authentication fails?
Up/down
Syntax to set a username/pass for use in PPP authentication
username caller hostname password password
Syntax to have a serial interface use CHAP
conf t
int s1/0
ppp authentication chap
2 useful debug commands for PPP
debug ppp authentication
debug ppp negotiation
What are the 2 primary attributes of a leased line?
Symmetrical speeds
Always on
What kind of cable goes between a router and a CSU?
DTE
What are the 5 fields in the HDLC header?
- Flag
- Address
- Control
- Type
- FCS
What field did Cisco add to their implementation of HDLC?
Type
What does the Cisco HDLC Type field help with?
It identifies which L3 protocol is contained in the packet.
What is the default encapsulation on a Cisco router’s serial interface?
Cisco HDLC
Command to set a serial interface to use HDLC
conf t
int s1/0
encapsulation hdlc
Command to verify if a serial interface is set up as a DTE or DCE
show controllers serial int number
Command to check encapsulation type on a serial interface
show interface serial int number
What types of WAN connections support asynchronous connections?
Serial line with PPP
How do the fields in a PPP header differ from that of HDLC?
They don’t.
What would lead to an up/down state on a serial interface?
- Encapsulation mismatch
- One side having keepalives disabled
- Authentication failure/mismatch
