WAN Technologies Flashcards
What is the most typical WAN speed in the US?
T1 - 1.544 Mb/s
Why is it important to match the bandwidth to the clockrate on a serial interface?
Because DRP’s often use the speed of a link to calculate routes.
How can you find out (besides looking at it) which end of a serial cable is the DTE and which the DCE side?
show controllers Serial 0/0/0
When looking at a serial cable, how can you tell which side is which?
The female side is the DCE side.
The male side is the DTE
Change the encapsulation on a serial link to PPP:
(In int config mode)
encapsulation PPP
Which side of a serial cable is the side that sets the speed of the link?
The DCE
LMI
Local Management Interface:
Local Management Interface (LMI) is a signaling standard used between routers and frame relay switches. Communication takes place between a router and the first frame relay switch it's connected to. Information about keepalives, global addressing, IP Multicast and the status of virtual circuits is commonly exchanged using LMI.
What is IPSec?
Internet Protocol Security
A suite of protocols for authenticating and encrypting each IP packet of a communications session.
What are the four critical features of IPSec?
- Authentication
- Data Integrity
- Confidentiality
- Replay Protection
What does GRE stand for? What is it?
Generic Routing Encapsulation
GRE is a tunneling protocol that allows routing protocols to run across tunnels. A GRE tunnel is a tunnel within a tunnel (so you can tunnel while you tunnel).
What command would you use on a frame relay network to view the number of incoming and outgoing packets on a virtual circuit?
show frame-relay pvc
What are three purposes/uses of tunneling?
- To allow users to access or provide services not offered by the underlying network.
- To provide services that are impractical or unsafe to be offered using only the underlying network services; eg. remote access.
- To hide the nature of the traffic running through the tunnel.
What is the device that interfaces (translates between) Ethernet and T1 lines?
CSU DSU
What is a leased line? Does it use a synchronous or asynchronous serial line?
A leased line is a dedicated point-to-point WAN connection leased by an Internet user (usually a business) from an ISP usually for flat a monthly fee. It’s a more expensive, high-performance WAN connection than a packet-switched connection.
They use synchronous serial lines.
Which WAN encapsulation types are used most often on leased lines?
HDLC and PPP
What is circuit switching? Give an example of a circuit switching technology.
The concept of this WAN connection is based on the typical telephone switching network. A connection needs to be established prior to be able to transfer data. This type of connection is used for low bandwidth data transfers where charging is calculated based on actual connection time.
ISDN (Integrated Services Digital Network) protocol is basically used on this connection type.
What is packet switching? Give an example of a packet switching technology.
Always-on connection, where available bandwidth is shared between several users. No time-based charging. Charging is based on committed traffic rate. This type of connection is more appropriate for bursty data transfers. Special configuration is needed to support strict QoS requirements.
Frame Relay is a packet switching connection type.
Which type of WAN encapsulation should you use if you are trying to communicate between a Cisco router and a router from another vendor?
PPP
Why can’t HDLC be used as the encapsulation protocol on a serial link between different-vendor routers?
Because every vendor has its own implementation of HDLC - there is no standard HDLC format.
Does HDLC support authentication?
No
What WAN encapsulation protocol is LCP associated with and what functions does it perform for this protocol?
Link Control Protocol (LCP) provides the means for configuring, establishing, maintaining and terminating a PPP connection. Among other things, LCP handles PPP authentication methods, error detection, compression techniques, support
for multilink etc.
What WAN encapsulation protocol is NCP associated with and what functions does it perform for that protocol?
Network Control Protocol (NCP) provides the means for encapsulating multiple network layer protocols across the PPP data link.
When configuring PPP authentication on a serial connection what should determine the usernames of your routers?
The username of each router should match the host name of the other router.
What is the recommended mask to use on a point-to-point serial link?
/30, which allows for 2 hosts. A /31 can also be used if subnet-zero is in use.
