Part 3: Routing Protocols and Concepts

What is a router?

A computer that connects multiple networks and delivers packets across them.

What components does a router share with other computers?

Common hardware components and an operating system

What is the primary function of a router?

to deliver packets across different networks

How does a router ensure network reachability 24/7?

By using alternate paths if the primary path fails.

How does a router support real-time traffic like voice and video ?

by using Qos (Quality of Sevice) to prioritze IP packets

How does a router help protect the network from attacks?

by permitting or denying the forwarding of packets

What is a routing table?

A data file in RAM that stores route information for networks.

What does the routing table contain?

Network/next-hop association to reach destinations

What is the “next hop” in a routing table?

The router or interface used to forward packets toward the destination

What is a directly connected network?

A network directly attached to one of the router’s interface.

What happens when a router interface is configured with an IP address?

It becomes a host on the attached network and is added to the routing table

What is a remote network?

A network not directly connected to the router requiring packet forwarding to another router.

How are remote networks added to the routing table?

Using dynamic routing protocols or static routes

What is a dynamic route?

A route learned automatically by the router via a dynamic routing protocol

What is a static route?

a route manually configured by a network administrator

Who makes the routing decision on a router?

the router makes i alone using its own routing table

Does one routers routing table affect another’s?

No, each router make decisions independentlyD

Does routing info for one direction imply info for the reverse path?

No, routing information is not bidirectional by default

What is static routing?

Manual configuration and selection of a network route by a network administrator

Is static routing a routing protocol?

No.

When should a static routes be used in a small network?

When a network consists of only a few routers.

When should static routes be used with an ISP?

When connected to the Internet through a single ISP

What is a hub-and-spoke topology?

A central hub connected to multiple branches (spokes), each with only one connection to the hub.

Why use static routing in a hub-and-spoke topology?

Because each branch has only one path to destinations: through the hub

What is one use of static routing in small networks?

Easier maintenance of routing tables.

What type of network commonly uses static routes for routing?

Stub networks

What is a single default route used for?

To represent a path to any network not matched by other routes.

List one advantage of static routing

Minimal CPU processing

List another advantages of static routing.

Easy for administrator to understand

List a third advantages of static routing

Easy to configure

List one disadvantage of static routing

Time consuming configuration and maintenance

What makes static routing error-prone in large networks?

Manual configuration

Why is static routing difficult in growing networks?

Maintenance becomes cumbersome.

What knowledge is required to implement static routing properly?

Completer knowledge of the entire network

What is the command to configure a static route?

ip route

What is the “network-address” parameter in ip route?

Destination network address to add to the routing table

What is the “subnet-mask” parameter in ip route?

Subnet mask of the remote network

What is the “ip-address” parameter in ip route?

next-hop router’s IP address

What is the “exit-interface” parameter in ip rouute?

Outgoing interface used to forward packets to the destination

What is a default static route?

A route that matches all packets when no more specific route exists

When is a default static route used?

When no other route matches a packet’s destination IP address

What is a common use of a default static route?

Connecting an edge router to an ISP network?

What is a stub router?

A router connected to only one other router

What is dynamic routing?

A set of processes, algorithms, and messages to exchange routing information and choose best paths.

What are the purpose of dynamic routing protocols?

Discover remote networks, maintain routing info, choose best path, find new path when needed

What are the main components of dynamic routing protocols?

Data structures, routing protocol messages, and algorithms

Where is routing protocol information stored?

In RAM

What are routing protocol message used for?

to discover neighbors, exchange routing info, and update network knowledge

What is the role of algorithms in routing protocols?

To facilitate routing info exchange and determine best paths

What happens when a router detects a topology change?

It advertises the change to other routers

How can routing protocols be classified by purpose?

Ad IGP (Interior Gateway Protocol) or EGP (Exterior Gateway Protocol)

How can routing protocols be classified by operation?

As distance vector, link-state, or path-vector protocols

How can routing protocols be classified by behavior?

As classful or classless protocols

What type of protocol is RIPv1?

IGP, distance vector, classful protocol.

What type of protocol is RIPv2?

IGP, distance vector, classless protocol.

What type of protocol is EIGRP?

IGP, distance vector, classless protocol (Cisco).

What type of protocol is OSPF?

IGP, link-state, classless protocol.

What type of protocol is IS-IS?

IGP, link-state, classless protocol.

What type of protocol is BGP?

EGP, path-vector, classless protocol.

What is an autonomous system (AS)?

A collection of routers under a common administration

What is IGP used for?

Routing within an autonomous system (intra-AS routing).

What is EGP used for?

Routing between autonomous systems (inter-AS routing).

Name examples of IGPs.

RIP, EIGRP, OSPF, IS-IS.

What is the only viable EGP today?

Border Gateway Protocol (BGP).