Chapter 3: Addressing and Routing

Question 1

IPv4

ExamAlert: Be prepared for questions asking you to identify IP class ranges, such as the IP range for a Class A network.

Answer 1

Composed of four sets of 8 binary bits, which are called octets (32 bits)

5 address classes (A-E) although only 3 (A, B, and C) assign addresses to clients; Class D reserved for multicast addressing; Class E reserved for future development

Unicast address: Single address specified; Data sent with unicast addressing is delivered to a specific node identified by the address; Point-to-point address link

Broadcast address: IP address used to target all systems on a subnet or network instead of single hosts

Multicast: Mechanism by which groups of network devices can send and receive data between the members of the group at one time, instead of separately sending messages to each device in the group.

Question 2

Subnet Mask

Pg. 97 Table 3.3 Default Subnet Masks Associated with IP Address Classes

Answer 2

Defines which parts of the IP address refer to the network address and which refer to the node address; Most commonly expressed in 32-bit dotted-decimal format

Question 3

Subnetting

Answer 3

A process by which the node portions of an IP address create more networks than you would have if you used the default subnet mask

Question 4

Broadcast domains vs Collision domains

Answer 4

Collision domains are all the connected nodes and broadcast domains are all the logical nodes that can reach each other; Collision domains are typically subsets

Question 5

Classless interdomain routing (CIDR)

Answer 5

An IPv4 method of assigning addresses outside the standard Class A, B, and C structure; Addresses assigned using a value known as the slash

Question 6

Default Gateway

Answer 6

The means by which a device can access hosts on other networks for which it does not have a specifically configured route

Question 7

IPv6

Pg. 107 Table 3.5 Comparing IPv4 and IPv6 addressing

Answer 7

Unicast IPv6 Addresses

Global Unicast Addresses: The equivalent of IPv4 public addresses that are routable and travel throughout the network

Link-Local Addresses: Designated for use on a single local network; Automatically configured on all interfaces

Site-Local Addresses: Equivalent to the IPv4 private address space; Routers do not forward site-local traffic outside the site; Must be assigned through either stateless or stateful address configuration proccesses

Note, stateless refers to IP autoconfiguration in which admins do not need to manually input configuration information and stateful configuration network devices obtain address information from a server

Question 8

Dynamic Host Configuration Protocol (DHCP)

Answer 8

The mechanism that enables a central system to provide client systems with IP addresses

Question 9

Settings used to connect to a TCP/IP network

Answer 9

IP address: Each system must be assigned a unique IP address so that it can communicate on the network

Subnet mask: Enables the system to determine what portion of the IP address represents the network address and what portion represents the node address

Default gateway: Enables the system to communicate on a remote network, without the need for explicit routes to be defined

DNS server addresses: Enables dynamic hostname resolution to be performed.

Question 10

Automatic Private IP Addressing (APIPA)

Answer 10

The function of APIPA is that a system can give itself an IP address if it is incapable of receiving an address dynamically from a DHCP server; Configures with address and appropriate subnet mask but no default gateway address

Question 11

Network Address Translation (NAT)

Answer 11

Enables the use of any addressing scheme on internal networks, though common practice to use private address ranges; Only one registered IP address required on the system’s external interface acting as the gateway between internal and external networks

Question 12

Port Address Translation (PAT)

Answer 12

All systems on the LAN are translated to the same IP address but with a different port number assignment; Used when multiple clients want to access the Internet

Question 13

Static Network Address Translation (SNAT)

Answer 13

Simple form of NAT that directly maps a private IP address to a static unchanging public IP address.

Question 14

Destination Network Address Translation (DNAT)

aka Port Forwarding

Answer 14

Can be implemented on any router to change the destination IP address on a packet and do the inverse operation on replies; Typically used between services located on a private network and IP addresses that are publicly accessible; Commonly referred to as port forwarding

Question 15

Routing table

Answer 15

Chart of best possible path for data to reach its destination

Question 16

Static routing

Answer 16

Routes and route information manually entered using the routing tables; Suited only for smaller environments

route add command adds a static route to the routing table

-p switch makes the static route persistent

Question 17

Dynamic routing

Answer 17

When routers use special routing protocols to pass information about themselves to other routers so that other routers can build routing tables

Question 18

Hops

Answer 18

Communication between distance-vector routers; On the network, each router represents one hop

Question 19

tracert

Answer 19

Used to see how many hops a packet takes to reach a destination

Question 20

Routing Information Protocol (RIP)

Answer 20

Maximum 15 hops, router updates required every 30 seconds, no authentication

Question 21

RIPv2

Answer 21

Authentication included, changed from network-wide broadcast to multicast, same hop limit

Question 22

Enhanced Interior Gateway Routing Protocol (EIGRP)

Answer 22

Uses neighbors to help determine routing information. Routers configured to use EIGRP keep copies of their neighbors’ routing information and query these tables to help find the best possible route for transmissions to follow

Question 23

Split Horizon

Answer 23

Works by preventing the router from advertising a route back to the other router from which it was learned

Question 24

Poison Reverse

Answer 24

Dictates that the router is advertised back on the interface from which it was learned but has a loop count of infinity which tells the node that the route is unreachable

Question 25

Convergence

Answer 25

The process by which routers learn of a change in routing

Question 26

Open Shortest Path First (OSPF)

Answer 26

A link-state routing protocol based on the shortest path first algorithm to find the least-cost path to any destination in the network; Used in medium to large enterprise networks because of tunneling features

Question 27

Intermediate system-to-intermediate system (IS-IS)

Answer 27

A link-state protocol that discovers the shortest path for data to travel using the SPF algorithm; Used in large ISP networks because of its stability features and because it can support more routers

Question 28

Border Gateway Protocol

Answer 28

Can be used between gateway hosts on the Internet

Question 29

Border Gateway Protocol

Answer 29

Can be used between gateway hosts on the Internet; Examines the routing table (contains list of known routers), the addresses they can reach, and a cost metric associated with the path to each router so that the best available route is chosen.

Question 30

Proxy Servers

Answer 30

Part of a firewall system, a server that sits between a client computer and the Internet, looking at the web page requests the client sends; Can use caching to increase response time and reduce bandwidth usage, but web page not always updated; Proxy servers can filter client requests

Question 31

Reverse proxy server

Answer 31

A server that resides near the web servers and responds to requests. Often used for load balancing purposes as each proxy can cache information from a number of different servers

Question 32

Spanning Tree Protocol

Answer 32

Designed to prevent switching loops from occurring; Actively monitors the network searching for redundant links and when found shuts them down.

Question 33

Trunking

Link Aggregation

Answer 33

Refers to the use of multiple networks cables or ports in parallel to increase the link speed beyond the limits of any one cable or port.

Using multiple cable to increase throughput

Question 34

Port mirroring

Answer 34

Monitor network traffic and how well a switch works; Admins configure a copy of all inbound and outbound traffic to go to a certain port; 802.1x authentication