ICND 1 Chapter 4 (Fundamentals of IPv4 addressing and routing)

What are 2 important facts about how IPv4 groups IP addresses?

-All IP addresses in the same group must not be separated from each other by a router -IP addresses separated from each other by a router must be in different groups

What are the goals of a routing protocol?

-dynamically learn and fill the routing table with a route to each subnet in the internetwork -If more than one route to a subnet is available, to place the best route in the routing table -To notice when routes in the table are no longer valid, and to remove them from the routing table -If a route is removed from the routing table and another route through another neighboring router is available, to add the route to the routing table - To work quickly when adding new routes or replacing lost routes -To prevent routing loops

What is the assignable range of values for the first octect for Class A IP networks?

0 to 127

Range for each octet is

0-255

Which layers of the OSI model does Ping check?

1, 2, 3

What are the 2 steps IPv4 hosts use for routing?

1. Destination IP in same subnet as I am, then send directly to destination host 2. Otherwise, send to my default gateway (default router)

All routing protocols use the same general steps for learning routes, which are...

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

What roughly are the steps a host will use DNS over a network?

1. Host requests connection to another host using a host name 2. The requesting host sends a DNS message (DNS query) to the DNS Server 3. The DNS server send back a DNS reply that lists the requested hosts IP address 4. The requesting host can now send IP packets to the destination host

What are the 2 simple steps to routing by an IPv4 host?

1. If the destination IP address is in the same IP subnet as I am, send the packet directly to that destination host 2. Otherwise, send the pack to my default gateway, also known as a default router (This router has an interface on the same subnet as the host.)

Two main concepts of routing

1. Process of routing forwards Layer 3 packets, also called Layer 3 protocol data units (L3 PDU), based on the destination Layer 3 address in the packet 2. Routing process uses the data link layer to encapsulate the Layer 3 packets into Layer 2 frames for transmission across each successive data link

Summarizing Router forwarding logic. If a router receives a data frame addressed to itself the router uses the following logic...

1. Use the data link Frame Check Sequence (FCS) field to ensure that the frame had no errors; if errors occurred, discard the frame 2. Assuming that the frame was not discarded at Step 1, discard the old data link header and trailer, leaving the IP packet 3. Compare the IP packet's destination IP address to the routing table, and find the route that best matches the destination address. This route identifies the outgoing interface of the router, and possibly the next-hop router IP address 4. Encapsulate the IP packet inside a new data link header and trailer, appropriate for the outgoing interface, and forward the frame

How many bytes are in a header? How many bits in a byte?

20, 8

How different IP address exist in IPv4?

2^32

How many bits are in an IP address

32

All network IDs from 1-126 are which class?

A

Define IP routing protocol

A protocol that aids routers by dynamically learning about the IP address groups so that a router know where to route IP packets so that they go to the right destination host

What is the benefit of requiring all nearby IP addresses to be in the same IP network of IP subnet?

A router can list one routing table entry for each IP network or subnet, instead of one entry for every single IP address

Which IP classes are unicast

A, B, C

What is an ARP reply

ARP defined protocol, that indeed lists bot the original IP address and the matching MAC address upon receiving an ARP request

What is an ARP request

ARP defined protocol, which is a message that asks the simple request "if this is your IP address, please replay with your MAC address."

What are the 2 types of ARP messages?

ARP request ARP reply

What protocol dynamically learns the data-link address of an IP host connected to a LAN?

Address resolution protocol (ARP)

Define IP addressing

Addresses used to identify a packet's source and destination host computer. Addressing rules also organize addresses into groups, which greatly assists the routing process

What is a multicast address?

An address used to send one packet to multiple hosts

All network IDs from 128-191 are which class?

B

All network IDs from 192-223 are which class?

C

What are IPv4 classes and their beginning number ranges?

Class A 1-126 Class B 128-191 Class C 192-223 Class D 224-239 Class E 240-255

How does the number of IP addresses relate to IP classes?

Class A can produce 16 million host per network, but only 126 network addresses Class B can produce 65K hosts per network, and 16K network address Class C can produce only 254 hosts per network, but 2 million networks

Which IP classes are experimental (now defined as for future use)

Class E

What does a router attempt to do with a packet once it receives it

Compares the packet's destination IP address to entries in the routing table, and makes a match

Which IP classes are multicast

D

What is the system that IP address are written in?

DDN (dotted-decimal notation)

Which protocol and feature requires a PC to learn information from some other server device? ARP, ping, or DNS?

DNS

The way TCP/IP lets a computer find an IP address used by a listed host name is by using

DNS (domain name system)

The network architecture in a network diagram displaying DNS processes shows the internetwork as a cloud because...

DNS do not care about the details of the network

For ease of memorization the parts of an IP header are organized into 5 parts each 4 bytes wide (20 bytes total). Part 5 of the IP header contains?

Destination IP address

An IP header will contain a 32-bit ________ and _______. The IP header also contains lots of information.

Destination IP address and Source IP address

What other utilities does the network rely on?

Doman name system (DNS), Address Resolution protocol (ARP), and ping

What does ARP do?

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

How may all the routers on a network learn the routes for all the IP networks and subnets in an TCP/IP network?

Enable the same routing protocol in a TCP/IP network, with the correct settings, thus the routers will send routing protocol messages to each other

For a PC to send an IP packet to the default router it must,

Encapsulate the IP packet in an Ethernet frame at the data link layer. The frame will use the data link layer (2) addressing in the frame header to ensure the nearby router receives the frame

What is a benefit of subnetting?

Fewer wasted IP addresses

What is required for routing logic to work?

Host must know IP of default router Routers must know how to forward packets to each and every IP network and IP subnet

How does an ARP table differ from an Routing table?

Hosts and routers will let ARP cache entries time out to clean up the table

Ping uses which protocol

ICMP (Internet Control Message protocol)

What are the 2 types of Ping messages?

ICMP echo request ICMP echo reply

What is an example of how a router determines which data link address to use to send a packet?

IP address Resolution Protocol (ARP)

Any device that has at least one interface with an IP address can send and receive IP packets, and is called an

IP host

TCP/IP groups IP addresses together so that addresses used on the same physical network are part of the same group. These groupings are called

IP network or an IP subnet

The original specifications for TCP/IP grouped IP addresses into sets of consecutive addresses called

IP networks

A routers IP routing table lists IP address groupings, these are called

IP networks and IP subnets

For better efficiency, routers will use _____ in there routing tables instead of _______.

IP subnets, instead of every single host IP address

For ease of memorization the parts of an IP header are organized into 5 parts each 4 bytes wide (20 bytes total). Part 2 of the IP header contains?

Identification Flags Fragment Offset

What does ARP (Address Resolution Protocol) do?

It is a method which any host or router on a LAN can dynamically learn the MAC address of another IP host or router on the same LAN.

A computer does not technically have an IP address, the ____ does

NIC

Many people use the term network ID, but others may use terms such as

Network number and network address

What has the TCP/IP software on a host?

OS and software that implements the network layer

What is an example outside of TCP/IP that functions in the network later?

OSPF DNS ARP Ping

What is a network identifier?

One reserved DDN value per network that identifies the IP network (The network ID cannot be used by a host as an address)

What does ping stand for?

Packet Internet Groper

What is a simple example of how distant router could learn the location of the 168.1.0.0 network. by other routers using routing

Router 1 knows the 168.1.0.0 network is connected to it. Knowing this, R1 would send a routing protocol to R2. R2 then learns that the 168.1.0.0 networks default router is R1. R2 would further share by sending a routing protocol to the next furthest router with the location to 168.1.0.0

IP focuses on the job of ________, in the form of ______, from the source host to the destination host.

Routing data IP packets

What does path selection refer to

Routing protocols, specifically how routing protocols select the best route among the completing routes to the same destination.

What information is inside an ARP message?

Sender's IP Sender's MAC Target IP Target MAC (unknown in ARP request)

For ease of memorization the parts of an IP header are organized into 5 parts each 4 bytes wide (20 bytes total). Part 4 of the IP header contains?

Source IP address

__________ defines methods of further subdividing the IPv4 address

Subnetting

For routing logic to work on both hosts and routers, each needs to know something about the ______ internetwork. Hosts need to know __________. Routers need know ________.

TCP/IP IP address of default gateways to know how to send to remote destination routes to know how to forward packet

What is a unicast address?

The address signifies a single host interface

Between each device in routing a packet, what happens at the data link layer?

The pack is deencapsulated and encapsulated again

Define IP routing

The process of hosts and routers forwarding IP packets (Layer 3 PDUs), while relying on the underlying LANs and WANs to forward the bits

For ease of memorization the parts of an IP header are organized into 5 parts each 4 bytes wide (20 bytes total). Part 3 of the IP header contains?

Time to live Protocol Header Checksum

For ease of memorization the parts of an IP header are organized into 5 parts each 4 bytes wide (20 bytes total). Part 1 of the IP header contains?

Version Length DS Field Packet Length

All routers use the same general process to route a packet, each router keeps>>

an IP routing table

The term classful IP network refers to

any Class A, B, or C network, because it is defined by Class A, B, and C rules

IP defines network layer addresses that ID..

any host or router interface that connects to a TCP/IP network

Using a postal service analogy, each IP network and IP subnet works like a postal. In that all nearby IPs (addresses in a zip) must

be in the same IP network or IP subnet

The term octet is a vendor-neutral term for..

byte

Whenever a host or router needs send a packet encapsulated in an Ethernet frame, it first

checks its ARP cache for the correct IP address and matching MAC address

What is the time between losing a route and finding a working replacement route called?

convergence

A default router can also be referred to as the

default gateway

When a PC analyzes a packets IP address and determines it is not located on its connected LAN it forwards the packet to a device that should have that information, this device is called

default router

While ping uses ICMP. ICMP does much more like...

defines many messages that devices can use to help manage and control the IP network.

An IP address of a packet matching an IP address in the routing table is also matched with..

directions that tell the router where to forward the packet next

Since routers are Layer 3 devices, what does that many for the IP address for the router?

each port on the router has its own unique IP address

A network engineer could configure every router by typing in all the routes for every router, instead it is easier to...

enable a routing protocol on all routers

True or False. Every single DNS server knows all the names and matching IP addresses.

false

Generally, The addresses in a single IP network have the same numeric values in the __________ part of all addresses in the network.

first

To make our lives easier, TCP/IP defines a way to use __________ to identify other computers

host names

End-user computers (called ______ in a TCP/IP network) work together to perform IP routing.

hosts

In particular, the network layer specifies...

how packets travel end to end over a TCP/IP network, even when the packet crosses many different types of LAN and WAN links

The reference text uses _________ to generally refer to a network made up various types of equipment

internetwork

What is in an IP routing table

lists IP address groupings, called IP network and IP subnets

What type of message is an ARP request if sent to everyone on the LAN? which layer is involved?

multicast, data link

Each network is briefly identified using a

network identifier

What layer is layer 3?

network layer

Each DDN has four decimal ____, separated by periods.

octets

IP does not concern itself with the ______transmission of data, but instead ________transmission of data

physical logical

IPv4 standards subdivide Class A, B, C unicast classes into

predefined subset IP networks of the DDN values inside the class

A routing protocol message sent from one router to the another that causes the other router to learn about a connected subnet is called...

routing update

Ping uses ICMP functions by

sending a message called an ICMP echo request to another IP address, while the receiving IP address replies with an ICMP echo reply

What defines protocols, as well as

standards for the text names used throughout the world, and a worldwide set of distributed DNS servers

subnet is just shorthand for

subdivided network

On Ethernet LANs, whenever a host of router needs to encapsulate an IP packet in a new Ethernet Frame, the hoist or router knows all the important facts to build that header, except

the destination MAC address

Whenever a host or router needs to encapsulate an IP packet in a new Ethernet frame, the host or router knows all the important facts to build that header, except

the destination MAC address

What does a host do with an ARP reply?

the host remembers the results, keeping the information in their ARP cache or ARP table.

The primary tool for testing basic network connectivity is

the ping commnad

Both IPv4 and IPv6 define

the same kinds of network layer functions, but with different details

How can you see the contents of the ARP cache of most PC operating systems?

using the arp -a command from a command prompt