Routing Protcols

7/26/2019 Routing Protcols

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Report

Major Routing Protocols

Submitted by: Saeed Ali Shahani (Intern)

Submitted to:(Solution Provisioning Engineering) SPE South Team

Date: 10-5-2016


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Table of Contents

1 What is Routing Protocol?...........................................................................................................3

1.1 Types of Routing .................................................................................................................3

1.1.1 Static Routing ..............................................................................................................3

1.1.2 Dynamic Routing Protocols ..........................................................................................3

1.2 Classification .......................................................................................................................3

1.3 Types of Routing Protocols ..................................................................................................4

1.3.1 Distance Vector ...........................................................................................................4

1.3.2 Link State .....................................................................................................................4

2 RIP (Routing Information Protocol) .............................................................................................5

3 EIGRP (Enhanced Interior Gateway Routing Protocol) ..................................................................6

4 OSPF (Open Shortest Path First) ..................................................................................................7

4.1 Introduction ........................................................................................................................7

4.2 OSPF Packet Type ................................................................................................................8

1. Hello: ..................................................................................................................................8

2. DD/DBD: .............................................................................................................................8

3. LSR: ....................................................................................................................................8

4. LSU: ....................................................................................................................................8

5. LSAck: .................................................................................................................................8

4.3 Router ID ............................................................................................................................8

4.4 Key points ...........................................................................................................................8

4.5 OSPF Tables:- ......................................................................................................................9

4.6 OSPF 7-States diagram ........................................................................................................9

4.7 LSA Types .......................................................................................................................... 10

4.8 Router and Area Types ...................................................................................................... 11

5 BGP (Border Gateway Protocol) ................................................................................................ 12

5.1 Introduction ...................................................................................................................... 12


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1 What is Routing Protocol?

The process of moving a packet of data from source to destination. Routingis usually performed by a

dedicated device called a router.

A routing protocol specifies how routers communicate with each other

A routing algorithm determine the specific choice of route

1.1 Types of Routing

1.

Static

2.

Dynamic

1.1.1 Static Routing

Hand type all network locations in routing table

Ideal for Small Organization Simplest form of Routing

One way communication

Static routes use less bandwidth than dynamic routes

No CPU cycles are used to calculate and analyze routing updates.

1.1.2 Dynamic Routing Protocols

Place information in routing table. If change occur it update the routing table automatically with all the

information

1.2 Classification

1. IGPstands Internal Gateway Protocol :work as a single autonomous number within small

organization

2.

EGPStands External Gateway Protocol :used for internet ISPs

IGP EGP RIP BGP (Border Gateway Protocol)

OSPF - EBGP (Exterior Border Gateway Protocol)

IGRP - IBGP (Interior Border Gateway Protocol)

EIGRP (Cisco Proprietary)


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1.3 Types of Routing Protocols

1.3.1 Distance Vector

It only look distance

Take shortest-path

Used in RIP,IGRP

1.3.2 Link State

Used in OSPF


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2 RIP Routing Information Protocol)

Routing Information Protocol (RIP) is a distance-vector routing protocol. RIP sends the complete routing

table out to all active interfaces every 30 seconds. RIP only uses hop count (the number of routers) to

determine the best way to a remote network.


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3 EIGRP Enhanced Interior Gateway Routing Protocol)

EIGRP is an enhanced version of IGRP. The same distance vector technology found in IGRP is also used in

EIGRP, It is a Cisco proprietary protocol.

It doesnt send link state packet like OSPF, but it send distance-vector plus reaching cost from

perspective of router

Best Path Selection with DUAL (Diffusing Update Algorithm)

Fast convergence

Efficient in neighbor discovery

Maximum Hop count 255

Load balancing over unequal cost links

Classless (VLSM support)

Hybrid routing protocol (distance vector that has link-state characteristics)

Multicast - 224.0.0.10

IP protocol 88

Neighbors advertise distance to specific network(s)

Default composite metric of bandwidth and delay

Load, reliability and MTU can be factored into metric

Send specific updates only when topology change occur

Admin distance is

-

90 for EIGRP internal routes

-

170 for EIGRP external routes

-

5 for EIGRP summary routes.

-


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4 OSPF Open Shortest Path First)

4.1 Introduction

Open-Shortest-Path-First (OSPF) is the most widely used interior gateway protocol routing protocol on

the world because it is a public (non-proprietary) routing protocol while its biggest rival, EIGRP, is a Cisco

proprietary protocol so other vendors cant use it. OSPF is a complex link -state routing protocol. Linkstate routing protocols generate routing updates only when a change occurs in the network topology.

When a link changes state, the device that detected the change creates a link-state advertisement (LSA)

concerning that link and sends to all neighboring devices using a special multicast address. Each routing

device takes a copy of the LSA, updates its link-state database (LSDB), and forwards the LSA to all

neighboring devices.

OSPF routers use LSA (Link State Advertisement) to describe its link state. LSDB stores all LSAs.

A router uses Router LSA to describe its interface IP addresses.

After OSPF is started on a router, it creates LSDB that contains one entry: this routers Router

LSA.


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4.2 OSPF Packet Type

5-type - 10/40 sec, 30/120 sec

1.

Hello:are used to establish and maintain adjacency with other OSPF routers

2. DD/DBD: The neighboring router with the highest priority is elected as the DR

3.

LSR:

used by receiving routers to request more information about any entry in the DBD

4. LSU:

used to reply to LSRs as well as to announce new information.

5.

LSAck:sent to confirm receipt of an LSU message

4.3 Router ID

The router is known to OSPF by the OSPF route id

By default the router id is the highest IP address on an active interface

A loopback interface can override the OSPF router id

The OSPF router id command can be used to override the OSPF router id

Using the loopback interface or router id command is recommended for stability

4.4 Key points

Is a public (non-proprietary) routing protocol. Is the only link-state routing protocol.

This works by using the Dijkstra algorithm

Information about its neighbors (local connectivity) is sent to the entire network using

multicasting

The entire routing table is transmitted once every 30 minutes

Routing information is shared through Link-state updates (LSAs)

HELLO messages are used to maintain adjacent neighbors

Is a classless routing protocol because it does not assume the default subnet masks are used. It

sends the subnet mask in the routing update. + Supports VLSM and route summarization

Uses COST as a metric which CISCO defines as the inverse of the bandwidth

Uses AREAs to subdivide large networks, providing a hierarchical structure and limit the

multicast LSAs within routers of the same area

Area 0 is called backbone areaand all other areas connect directly to it. All OSPF networks

must have a backbone area

Area Border Routers (ABR) are any routers that have one interface in one area and another

interface in another area


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4.5 OSPF Tables:-

Neighbor Table: - Adjacency Database, List of recognized neighbor

Topology Table: - Contain all routers & their attached links in the area; LSDB

Routing Table: - Best path to destination

4.6 OSPF 7-States diagram


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4.7 LSA Types

OSPF Virtual Link: - Once the ospf router becomes adjacencies then the virtual link will be up. If

between the routers there is firewall then we need to open port 89 first. Area cant be stub area.

At least one end reside at area 0

Both end router must share the common area

Route Summarization: - Route summarization can reduce the number of routes that a router

must maintain, because it is a method of representing a series of network in a single summary

address


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4.8 Router and Area Types


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5 BGP Border Gateway Protocol)

5.1 Introduction

Border Gateway Protocol (BGP) is a standardized exterior gateway protocol designed to exchange

routing and reachability information between autonomous systems (AS)on the Internet.

The protocol is often classified as a path vector protocolbut is sometimes also classed as a distance

vector routing protocol. The Border Gateway Protocol makes routing decisions based on paths, network

policies, or rule-setsconfigured by a network administrator and is involved in making core routing

decisions.

BGP may be used for routing within an autonomous system. In this application it is referred to as

Interior Border Gateway Protocol, Internal BGP, or iBGP. In contrast, the Internet application of the

protocol may be referred to as Exterior Border Gateway Protocol, External BGP, or EBGP.

Figure


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5.2 Multihoming Environment

Having two or more upstream providers for internet connectivity is considered as Multihoming

Environment. Multihoming ensures redundancy with best available path towards the specified

destination. BGP is considered as the best protocol to be used in this environment.

Following techniques are available to implement Multihoming

5.2.1 Stub Network

Two or more links to the same ISP

No need for BGP

Point static default to upstream ISP oUpstream ISP advertises stub network

Policy confined within upstream ISPs policy

5.2.2 Multihomed Stub Network

Two or more links to different ISPs Through a Single Local Router

Use BGP (not IGP or static) to load share

Use private AS (ASN > 64511) oUpstream ISP advertises stub network

Policy confined within upstream ISPs policy


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5.2.3 Multihomed Network

Two or more links to different ISPs Through Multiple Local Routers

Many scenarios are possible

-Multiple sessions to same ISP

-Secondary for backup only

-Load-share between primary and secondary

-Selectively use different ISPs

5.3 BGP over OSPF

The first reason is that BGP is more scalable than OSPF.

E.g. the ISP level of routing do had large number of routes, which igp routing protocols like ospf cannot

handle. BGP can handle such large routes between AS.

Second reason is that bgp allows more options for routing manipulations and optimization by using

routing policies (by manipulating attributes)which is required when routing between AS , and this,

normal igp like ospf cannot perform.


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Routing Protcols