Routing

Router

Forwards traffic between subnets, between an internal and external network, or between two external networks

Routing table

Helps determine which route entry is the best fit for the network

Directly Connected Route

Learned by physical connection between routers

Static Route

Manually configured by an administrator

Dynamic Route

Learned by exchanging information between routers

Posion Reverse

Cause a route received on one interface to be advertised back out of that same interface with a metric considered to be infinite

Split Horizon

Prevents a route learned on one interface from being advertised back out of that same interface

Interior Gateway Protocol (IGP)

Operates within an autonomous system

Exterior Gateway Protocol (EGP)

Operate between autonomous systems

Distance Vector

Sends a full copy of routing table to its directly connected neighbors at regular intervals. It has slow convergence time and uses hop count as metric

Convergence

Time it takes for routers to update their routing tables in response to a topology change

Hold-down Timer

Prevents updates for a specific period of time and speeds up convergence

Hop count

Number of routers from the source router through which data must pass to reach the destination network

Link State

Requires all routers to know about the paths that all other routers can reach in the network

Routing Information Protocol (RIP)

A distance vector protocol that uses hop count (maximum hops of 15; 16 is infinite) (Update every 30 secs, eay to configure, runs over UDP)

Open Shortest Path First (OSPF)

A link state protocol that uses cost is classless routing protocol

Intermediate System to Intermediate System (IS-IS)

A link-state routing protocol similar in its operation to OSPF. IS-IS uses a configurable, yet dimensionless, metric associated with an interface and runs Dijkstra's shortest path first algorithm. Although using IS-IS as an IGP offers the scalability, fast convergence, and vendor interoperability benefits of OSPF, it has not been deployed as widely as OSPF.

Enhanced Interior Gateway Routing Protocol (EIGRP)

Hybrid of distance vector and link state protocols that uses bandwidth and delay (hops)

Border Gateway Protocol (BGP)

path vector using the number of autonomous system hops rather than router hops; runs the backbone of the internet. (Widespread utilization, Slow convergence)

Route Believability

If a route has a lower administrative distance (AD), the route is more believable

Network Address Translation (NAT)

Used to conserve the limited supply of IPv4 addresses( Translates private IP addresses to public IP addresses for routing over public network

Dynamic NAT (DNAT)

Automatically assigns an IP address from a pool and gives a one-to-one translation

Static NAT (SNAT)

Manually assigns an IP address and gives a one-to-one translation. Used as a security feature

Port Address Translation (PAT)

Sharing of one public IP by multiple private IP addresses which gives a many-to-one translation

Multicast Routing

Multicast sender sends traffic to a class D IP address known as a multicast group its goal is to send the traffic only to the devices that want it

Internet Group Management Protocol (IGMP)

Lets routers know which interfaces have multicast receivers and allows clients to join a multicast group

Protocol Independent Multicast (PIM)

Routes multicast traffic between routers and forms a multicast distribution tree

PIM Mode (PIM-DM)

Uses periodic flood and prune behavior to form optimal distribution tree

PIM Sparse Mode (PIM-SM)

Uses a shared distribution tree and creates an optimal distribution tree through shortest path tree (SPT) switchover