Fundamentals of WANs and IP Routing

Question 1

Wide-area network (WAN)

Answer 1

Define
- physical (Layer 1) standards
- data-link (Layer 2) protocols
to communicate 
- over long distances  (leased-line WANs and Ethernet WANs)

Question 2

Leased line

Answer 2

Can be tought as a crossover cable between two routers, providing a Layer 1 service in full duplex at fixed speed.
Does not define a data-link layer protocol

Question 3

High-Level Data Link Control (HDLC)

Answer 3

Oner of the two most known and used protocols in leased lines (The other is PPP)

Question 4

Point-to-Point Protocol (PPP)

Answer 4

Oner of the two most known and used protocols in leased lines (The other is HDLC)

Question 5

HDLC Fields

Answer 5

• Flag (pattern to identifies a new arriving frame)
• Address (destonation device, useless being a point to point connection
• Control (no longer in use today)
• Type (type of Layer 3 packet)
• FCS (like Ethernet FCS)

Question 6

ISO HDLC

Answer 6

Does not have a Type field.

Cisco uses a proprietary variation that adds Type

Question 7

Ethernet WAN basics

Answer 7

• Works much like an Ethernet crossover cable—just over a WAN
• Logically, behaves like a point-to-point connection between two routers
• Physically, behaves as if a physical fiber Ethernet link existed between the two routers

Question 8

Internet Protocol (IP)

Answer 8

Focuses on the job of routing data, in the form of IP packets, from the source host to the destination host.

Question 9

Path selection

Answer 9

The term is sometimes used to refer to the routing process, while at other times, it refers to routing protocols, specifically how routing protocols select the best route among the competing routes to the same destination

Question 10

IP routing table

Answer 10

Lists IP address groupings, called IP networks and IP subnets.

Question 11

IP Address Resolution Protocol (ARP)

Answer 11

Dynamically learns the data-link address of an IP host connected to a LAN.

Question 12

Internetwork

Answer 12

More generally a network made up of routers, switches, cables, and other equipment

Question 13

Foundational rules of subnetting

Answer 13

• Two IP addresses, not separated from each other by a router, must be in the same group (subnet)
• Two IP addresses, separated from each other by at least one router, must be in different groups (subnets).

Question 14

Routing protocols general steps for learning routes

Answer 14

1. Each router, independent of the routing protocol, adds a route to its routing table for each subnet directly connected to the router
2. Each router’s routing protocol tells its neighbors about the routes in its routing table, including the directly connected routes and routes learned from other routers
3. After learning a new route from a neighbor, the router’s routing protocol adds a route to its IP routing table, with the next-hop router of that route typically being the neighbor from which the route was learned.

Question 15

Routing update

Answer 15

A routing protocol message causing the reciver to learn about subnet in the routing table of the sender

Question 16

Basic DNS Name Resolution Request

Answer 16

1. PC sends a DNS message —a DNS query— to the DNS server
2. DNS server sends back a DNS reply that lists remote server’s IP address
3. PC can send an IP packet to destination address IP of the remote server

Question 17

Ping (Packet Internet Groper)

Answer 17

The primary tool for testing basic network connectivity.
It uses the Internet Control Message Protocol (ICMP), sending a message called an ICMP echo request to another IP address. The computer with that IP address should reply with an ICMP echo reply