What is a router?
A router is a device that joins two or more networks and passes packets from one network to another
What are the categories of routers?
- Core routers (interior routers) — Direct data between networks within the same autonomous system (AS)
- Edge routers (border routers) — Connect an autonomous system with an outside network
- Exterior routers — Refers to any router outside the organisation’s AS
What is an AS?
An autonomous system (AS) is a collection of networks under a common administration (a single organisation, ISP, or systems administrator) and sharing a common routing strategy
What layer of the OSI model do routers operate at?
Network Layer (Layer 3)
What are the two types of multilayer switches?
- Layer 3 switches - capable of interpreting layer 3 data and works much like a router.
- Layer 4 switch - capable of interpreting layer 4 data
What is a routing table?
A routing table is a database that maintains information about where hosts are located and the most efficient way to reach them. They contain IP addresses and network masks that identify a network that a host or another router belongs to
What are the two types of routing paths?
- Static routing - Network administrators configures a routing table to direct messages along specific paths
- Dynamic routing - automatically calculates the best path between two networks and maintains this information in a routing table
What are routing protocols?
Routing protocols are protocols used by routers to communicate with each other to determine the best path
What is Administrative distance (AD)?
Administrative distance is a number indicating a protocol’s reliability
What is convergence time?
Convergence time is the time it takes to recognise the best path in the event of a change or network outage
What is overhead?
The burden placed on the underlying network to support the protocol
What are the two types of routing protocols?
- IGP (interior gateway protocols) - these are used by core routers and edge routers within autonomous systems and are often grouped according to the algorithms they use to calculate best paths
- EGP (exterior gateway protocols) - Used by edge routers and exterior routers to distribute data outside of autonomous systems (BGP is the only EGP currently in use)
What are distance-vector routing protocols?
distance-vector routing protocols calculate the path on the basis of the distance to the destination
What are link-state routing protocols?
Enables routers to communicate beyond neighbouring routers in order to independently map the network and determine the best path
What is OSPF?
OSPF (Open Shortest Path First) is an IGP and link-state protocol used on interior or border routers (is an improvement to RIP)
What is IS-IS?
IS-IS (Intermediate system to intermediate system) is an IGP and link-state routing protocol. Used for core routers and is not handcuffed to IPv4
What is EIGRP
EIGRP (Exterior Interior Gateway Routing Protocol) is an advanced distance-vector protocol that combines some of the features of a link-state protocol
