Fundamentals of WANs and IP Routing Flashcards Preview

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Flashcards in Fundamentals of WANs and IP Routing Deck (17)
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Wide-area network (WAN)

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


Leased line

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


High-Level Data Link Control (HDLC)

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


Point-to-Point Protocol (PPP)

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


HDLC Fields

- 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)



Does not have a Type field.
Cisco uses a proprietary variation that adds Type


Ethernet WAN basics

- 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


Internet Protocol (IP)

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


Path selection

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


IP routing table

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


IP Address Resolution Protocol (ARP)

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



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


Foundational rules of subnetting

- 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).


Routing protocols general steps for learning routes

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.


Routing update

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


Basic DNS Name Resolution Request

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


Ping (Packet Internet Groper)

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