CCNA Module 8

Network Layer

Facilitates data exchange between end devices.

IPv4

Primary protocol for network layer communication.

IPv6

Next-generation protocol with expanded address space.

Addressing

Identifying end devices in a network.

Encapsulation

Wrapping transport layer data in IP packets.

Routing

Determining packet paths through the network.

De-encapsulation

Extracting transport layer data from IP packets.

Connectionless

No pre-established connection before sending packets.

Best Effort

No delivery guarantees for sent packets.

Media Independent

IP operates regardless of physical media type.

Maximum Transmission Unit (MTU)

Largest packet size allowed on a network.

Fragmentation

Splitting packets into smaller units for transmission.

Latency

Delay caused by packet fragmentation.

NAT

Network Address Translation; modifies IP addressing.

IPv4 Header

Contains essential routing information for packets.

IPv4 Address Depletion

Exhaustion of available IPv4 addresses.

End-to-End Connectivity

Direct communication without intermediate address translation.

Network Complexity

Increased issues due to NAT implementation.

IETF

Internet Engineering Task Force; developed IPv6.

128-bit Address

IPv6 address length

40 Bytes Header

Fixed size of IPv6 packet header.

Extension Headers (EH)

Optional headers for additional network layer info.

Header Checksum

Field removed in IPv6 for performance improvement.

Fragment Offset

Field indicating packet fragment position

Host Forwarding Decision

The process by which a host determines whether to send packets to itself

Default Gateway

A router or layer 3 switch that has an IP address in the same range as the LAN and can forward traffic off the LAN.

Static Route

A route that must be configured manually and adjusted by the administrator when there is a change in the topology.

Dynamic Routing

A method where routes are automatically discovered and maintained

Routing Table

A list of all known network addresses (prefixes) and where to forward packets.

Internet Control Message Protocol (ICMP)

A network layer protocol used for error messages and operational information exchange.

Best Effort Delivery

A service model where the network does not guarantee delivery of packets.

Unreliable

A characteristic of a protocol that does not guarantee the delivery of packets.

Data Payload

The actual data being transmitted in a packet

Packet

A formatted unit of data carried by a packet-switched network.

Network Layer PDU

IP Packet

IP Header

The portion of an IP packet that contains control information

Traffic Class

A field in the IPv6 header that indicates the priority of the packet.

Flow Label

A field in the IPv6 header used to identify packets that require special handling.

Hop Limit

A field in the IPv6 header that specifies the maximum number of hops a packet can take before being discarded.

Local Host

A device that is on the same local area network (LAN) as the source device.

Remote Host

A device that is not on the same local area network (LAN) as the source device.

Next Hop

The next device that a packet will be sent to on its way to its destination.

Administrative Distance

A value used by routers to determine the trustworthiness of a route source.

Metric

A value that represents the cost of using a route