Ccna- Fundamentals Ipv4 Addressing And Routing

Front 1

IP routing

Back 1

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

Front 2

IP addressing

Back 2

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.

Front 3

IP routing protocol

Back 3

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

Front 4

Address Resolution Protocol (ARP)

Back 4

ARP dynamically learns the data link

address of an IP host connected to a LAN.

Front 5

Routing as covered so far has two main concepts:

Back 5

The 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.

■ The routing process uses the data link layer to encapsulate the Layer 3 packets into Layer

2 frames for transmission across each successive data link.

Front 6

two important facts about how

IPv4 groups IP addresses:

Back 6

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.

Front 7

Class A

Back 7

First Octet Range 1 to 126

Valid Network Numbers

1.0.0.0 to 126.0.0.0

Front 8

Class B

Back 8

128 to 191

128.0.0.0 to 191.255.0.0

Front 9

Class C

Back 9

192 to 223

192.0.0.0 to 223.255.255.0

Front 10

subnet

Back 10

shorthand for subdivided network

Front 11

IPv4 Host Routing

Back 11

Two step logic:

Step 1. If the destination IP address is in the same IP subnet as I am, send the packet

directly to that destination host.

Step 2. Otherwise, send the packet to my default gateway, also known as a default

router. (This router has an interface on the same subnet as the host.)

Front 12

Router Forwarding Logic

Step 1

Back 12

Use the data link Frame Check Sequence (FCS) field to ensure that the frame had no errors; if errors occurred, discard the frame

Front 13

Router Forwarding Logic

Step 2

Back 13

Assuming that the frame was not discarded at Step 1, discard the old data link header and trailer, leaving the IP packet.

Front 14

Router Forwarding Logic

Step 3

Back 14

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.

Front 15

Router Forwarding Logic

Step 4

Back 15

Encapsulate the IP packet inside a new data link header and trailer, appropriate for the outgoing interface, and forward the frame

Front 16

goals of a routing protocol

Back 16

To dynamically learn and fill the routing table with a route to each subnet in the

internetwork.

Front 17

goals of a routing protocol

Back 17

If more than one route to a subnet is available, to place the best route in the routing

table.

Front 18

goals of a routing protocol

Back 18

To notice when routes in the table are no longer valid, and to remove them from the

routing table.

Front 19

goals of a routing protocol

Back 19

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. (Many people view this

goal and the preceding one as a single goal)

Front 20

goals of a routing protocol

Back 20

To work quickly when adding new routes or replacing lost routes. (The time between losing

the route and finding a working replacement route is called convergence time.)

Front 21

goals of a routing protocol

Back 21

To prevent routing loops

Front 22

Address Resolution Protocol (ARP)

Back 22

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

Front 23

ARP Request

Back 23

a message that asks the simple request “if this is your IP address, please reply with your MAC address.”

Front 24

ARP Reply message

Back 24

lists both the original IP address and the matching MAC address.

Front 25

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Back 25

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