Routing Protocols

Question 1

Interior Gateway and Exterior Gateway
Routing Protocols fall into two categories:
Link State and Distance Vector

Answer 1

Types of Routing Protocols

Question 2

allow routers to dynamically learn and share routes with one another
Autonomous System
Adds fault Tolerance
Routing protocols: RIP (not used anymore), IGRP (not used anymore instead EIGRP- developed by Cisco),
EIGRP, OSPF, BGP, IS-IS
(EGP- not used anymore- obsolete)

Answer 2

Routing Protocols

Question 3

Share routes in a single Autonomous System

RIP, IGRP, EIGRP, OSPF, IS-IS

Answer 3

Interior Gateway Protocols

Question 4

Share routes between Autonomous Systems
BGP - border gateway protocol (local inside)
and EGP

Answer 4

Exterior Gateway Protocols

Question 5

OSPF = Open Shortest Path File which uses the Dykstra Algorithm
IS-IS = Intermediate System to Intermediate System

Answer 5

Link State

Question 6

measures hops between nodes based on local updates from all your neighbors
Uses the Bellman Ford Dual Algorithm (it’s a popular algorithm)
IGRP = Interior Gateway Routing Protocol
EIGRP = Enhanced Interior Gateway Routing Protocol (inside an organization)
BGP = Border Gateway Protocol (Exterior Gateway Protocol)

Answer 6

Distance Vector

Question 7

A complex system that can assume almost complete responsibility for a task without human input, verification, or decision making.
IGP= Interior Gateway Protocol
Routers that run on the same IGRP are considered an Autonomous System

Answer 7

Autonomous System

Question 8

Interior Gateway Protocol (IGP) within Autonomous System
Distance Vector
Hop Count is the only metric max of 15 hops
RIPv1 - Classful like IGRP which means that only does routing based on the class system of A, B, C
RIPv2 (modern routing protocols) - Classless which supports routing with any subnet mask

Answer 8

RIP (Router Information Protocol)

Question 9

Cisco proprietary routing protocol
Uses composite metric based on bandwidth, delay, load and reliability
Interior Gateway within Autonomous System (like RIPv2, IGRP and OSPF)
Hybrid or Advanced Distance Vector
Simple to configure and loop free
Rapid convergence
supports unequal cost path load balancing
Topology table and Neighbor table
Uses Successor (is a primary best route to a destination network) and Feasible Successor (secondary route to destination network)

Answer 9

EIGRP (Enhanced Interior Gateway Routing Protocol)

Question 10

EIGRP and OSPF both have fast convergence

for routers to participate in EIGRP with each other they must be part of the same Autonomous System

Answer 10

Most widely used Interior Gateway Routing Protocols

Question 11

Interior Gateway Protocol (IGP) within an Autonomous System
Link-State, Dijkstra
Metric: Path Cost
Uses Hierarchical Areas
Area 0 is the "backbone area"
Area Border Router (ABR)
Autonomous System BR (ASBR)

Answer 11

OSPF (Open Shortest Path First)

Question 12

Message Types:
Hello
Link State Request (LSR)
Link State Update (LSU)
Link State Acknowledgement (LSA)
is the most widely used Interior Gateway Routing Protocol

Answer 12

OSPF (Open Shortest Path First)

Part II

Question 13

Exterior Gateway - can be in different autonomous systems
eBGP: outside AS (deals with the Internet) is used to peer between different autonomous systems
iBGP: private
BGPv4: Internet Provider routing protocol of the internet
Path-vector/Distance-vector
Like EIGRP, BGP is also referred to as a “Hybrid” routing protocol at times
Manually configured neighbor relationships
Neighbors are called BGP peers

Answer 13

BGP (Border Gateway Protocol)

Question 14

is a number used to rank directly connected routes, static routes, and dynamic routes from most desirable (0) to least desirable (255)
If multiple routes exist to a specific destination then the route with the lowest administrative distance will be chosen
AD can be manually changed on the router
AD ranks “Trustworthiness” of a route

Answer 14

Administrative Distance