Networks Quiz - Routing

router

routers forward packets based on their destination IP address

• the hardware and IP is the software that makes internet technology work

datagram forwarding

• datagrams rely on routers to move them towards their final destination

• routers use a routing table to decide where to send each datagram

  • each router keeps a list of networks in the next hop of the next IP on the track

next hop

the next device on the datagrams journey to its final destination

routing table

devices have routing tables that list destinations debating on the IP address of that datagram

static route

manually configured and does not adapt automatically that means a route is entered into a routing table

default route

• used in a last resort situation, it’s used when no routes match which handles all destinations not in the table

route print

allows you to see the routing table of your device

NAT

allows multiple private deices to share a single glovally valid IP address

• expanded the lifespan of IPv4

• often used in residental networks

outgoing NAT translation

is how a router swaps your device's private IP address with a public one when sending traffic to the internet — so the outside world knows where to send the response back.

incoming NAT translation

is how a router receives traffic from the internet and forwards it to the correct device on your private network.

port translation

when a router maps a specific port on your public IP to a specific device and port on your private network.

port forwarding

a rule you manually configure on a router to always send traffic arriving on a specific public port to a specific device and port inside your private network

Dynamic NAT

allows a larger # of computers to share a smaller # of IP addys

dynamic routing

allow routers to exchange information with each other

interior gateway protocols (IGP)

are routing protocols used inside a single organization's network, sharing route information between routers within the same administrative domain

exterior gateway protcols (EGP)

are routing protocols used between different organizations or networks on the internet, sharing route information across administrative boundaries (e.g., BGP).

metrics

relational values used by routers when they have 1 or more routes to a netowork, the route with a lower metric # will be the one used to send data

common metrics

• hop count

• bandwith

• delay

• cost

distance vector routing

a method where each router shares its routing table with its direct neighbors, and each router calculates the best path based on distance (hop count) and direction (which neighbor to send it to).

convergence

the process by which all routers in a network reach a consistent, agreed-upon understanding of the network topology — meaning every router has the same, up-to-date routing table

rerouting

the process of redirecting network traffic to an alternate path when the primary path becomes unavailable or suboptimal

BGP border gateway protocol

• the protocol used on the Internet for exterior routing

• a hybrid routing protocol

link state dynamic routing protocols

a full map of the network and use the shortest past algorithms

open shortest path first - OSPF

a Link State routing protocol and one of the most widely used Interior Gateway Protocols (IGP) in enterprise and service provider networks. It's called "open" because it's based on an open standard (RFC 2328), unlike proprietary protocols like EIGRP.

LSA

link state advertisments

IS - IS - intermediate system to intermediate system

• a dynamic link state protocol that can be used as an alternative to OSPF

• sends updates only instead of sending the entire table over intervals

  • compatable with IPv6

EIGRB

a protocol that routers use to share route information with each other and find the best path to every destination.

administrative distance (route preference)

value used to rate trust worthiness of a route source when multiple protocols propose routes

managed devices

routers are a type of managed device which means they have a configuration interfaceso they can be setup and managed

MTU

the largest chunk of data that can be sent in one piece across a network link

fragmentation

the process of breaking a large packet into smaller pieces so it can travel across a network link that has a smaller MTU

fragmentation fields

Identification (16 bits) A number shared by all fragments of the same original packet so the receiver knows which pieces belong together.

Flags (3 bits) Three control bits:

• Bit 0 — reserved, always 0

• DF (Don't Fragment) — if set, the packet must not be fragmented; drop it and send an ICMP error instead

• MF (More Fragments) — if set, more fragments are coming; the last fragment has this as 0

Fragment Offset (13 bits) Tells the receiver where in the original packet this fragment belongs, measured in 8-byte units, so fragments can be reassembled in the correct order.

TTL - time to live

A field in the IPv4 header that limits how long a packet can travel across a network.

It's a simple counter — every router the packet passes through decreases it by 1. When it hits 0, the packet is discardedand an ICMP "Time Exceeded" message is sent back to the sender.