Enhance Interior Gateway Routing Protocol

Published Date: 02 Nov 2017

A protocol is the set of instruction or it is consists of digital message formats and some instruction for exchanging the messages in or between computing systems.. Protocols may include authentication and error detection and correction capabilities. Mainly all routing protocols work on Layer 3 (Network Layer) of the OSI Model. There are two different types of protocol one is connection oriented and other is connection less protocol. Connection oriented protocol are those protocol which requires a proper connection before sending the data to the destination e.g. Transmission Control Protocol (TCP). Connectionless protocols are those protocols which do not require any connection before sending the data or we can say that they do not require handshake, e.g. is User Datagram Protocol (UDP).

Routing protocols are mainly used by the router. It specifies how different router communicates with each other or how they will transmit the information to each other. The algorithm of routing protocol decides the specific route for transmitting the data. There are two types of routing protocol:-

Interior Gateway Protocol: - It depends upon distance and therefore known as distance vector routing protocol invented by CISCO. It exchanges routing data within an autonomous system. OSPF and ISIS is the example of routing protocol.

Exterior Gateway Routing Protocol: - It is a routing protocol used to transmit the data between two different autonomous systems. BGP is the example of exterior gateway routing protocol.

Following are the various term related to the Routing Protocol

A routing domain is a group of routers under the control of a single administrative entity, running a common interior routing protocol.

An autonomous system consists of a collection of routers under the control of a single administrative entity - for example, all the routers belonging to a particular ISP, corporation or university

Advantages & Disadvantages of Routing Protocols

Compared to manual configuration, much easier to maintain in large networks

Represent a point of failure that attackers can exploit

Can take some time for a router on one side of a large network to learn about a topology change on the other side of the network

Advanced routing protocols can be very complex

Inherent lack of control. For eg: if there are multiple paths to a destination network, routing protocol will decide which one to use. While metrics can be manually tweaked to make one path preferred, one needs to understand the consequences of the manual changes.

Following are the some of the Routing Protocol with their explanation and configuration along with the diagrams:-

Open Shortest Path First (OSPF):- It is link state routing protocol. This protocol mainly used in large enterprises to transmit the data. It routes IP packets within the same autonomous system. It is based on Dijkstra algorithm. In this initially a shortest path tree is made and then the routing table is made with the resulting best path. Like EIGRP, it does not support both IP and IPv6 routed protocols. Moreover it has unlimited hop count. Following is the configuration of OSPF

Configuration for Router01

router01>enable 

router01#configure terminal

router01 (config)#interface s0/s

router01(config-if)#ip address 172.16.0.1 255.255.0.0

router01(config-if)#no shutdown

router01(config)#ospf 1

router01(config-router)#network 172.16.0.0 0.0.255.255 area 0

router01(config-router)#network 172.17.0.0 0.0.255.255 area 0

router01(config-router)#exit

router01(config)#exit

router01#

Configuration for Router02C:\Users\user\Desktop\Untitled.png

router02>enable

router02#configure terminal

router02(config)#interface s0/0

router02(config-if)#ip address 172.17.0.2 255.255.0.0

router02(config-if)#no shutdown

router02(config-router)#network 172.17.0.0 0.0.255.255 area 0

router02(config-router)#network 172.18.0.0 0.0.255.255 area 0

router02(config-router)#network 172.19.0.0 0.0.255.255 area 0

router02(config-router)#exit

router02(config)#exit

To view the Routing table we can use the following command

router01#show ip route

Advantages of OSPF

OSPF is link-state routing protocol

RIP, IGRP and EIGRP are distance-vector (routing by rumor) routing protocols, susceptible to routing loops, split-horizon, and other issues.

OSPF has fast convergence

RIP and IGRP hold-down timers can cause slow convergence.

OSPF supports VLSM and CIDR

Cisco’s OSPF metric is based on bandwidth

RIP is based on hop count

IGRP/EIGRP bandwidth, delay, reliability, load

OSPF only sends out changes when they occur.

RIP sends its update on routing table in every 30 seconds, while IGRP sends its update in every 90 seconds to the neighboring router.

Extra: In case of OSPF, a router populated its own LSAs when its age arrive at 30 minutes (later)

OSPF also has the property of hierarchical routing.

Two open-standard routing protocols to choose from:

RIP, simple but very limited, or

OSPF, robust but more easy and simple to implement

Routing Information Protocol: - It is a distance vector routing protocol. It uses hop count as routing metric. It has maximum fifteen hop count after that it consider that path as an infinite distance. RIP is a most stable protocol because it implement split horizon, route poisoning and hold-down process for preventing the incorrect routing information. There are two version of RIP that is RIP1 and RIP2. RIP version one supports only class full network but RIP version two can support both class full as well as classless network. This protocol sends its complete routing tables to all the existing interfaces at some interval of time. In RIP the timers and loop avoidance schemes are the same for both versions. It supports load balancing over same cost path.

Configuration of Routing Information Protocol on router: -

Configuration of router 1

router01>enable 

router01#configure terminal.

router01(config)#interface s0/0

router01(config-if)#ip address 172.16.0.1 255.255.0.0

router01(config-if)#no shutdown

router01(config)#router rip

router01(config-router)#version 2

router01(config-router)#network 172.16.0.0

router01(config-router)#network 172.17.0.0

router01(config-router)#exit

router01(config)#exit

router01#C:\Users\user\Desktop\Untitled 2.png

Configuration of router2

router02>enable 

router02#configure terminal

router02(config)#interface s0/0

router02(config-if)#ip address 172.18.0.1 255.255.0.0

router02(config-if)#no shutdown

router02(config)#router rip

router02(config-router)#version 2

router02(config-router)#network 172.17.0.0

router02(config-router)#network 172.18.0.0

router02(config-router)#network 172.19.0.0

router02(config-router)#exit

router02(config)#exit

router02#

Advantages and Drawbacks of RIP.

Simpler to understand and implement (compared to OSPF, for example) and is suitable for small networks

Not suitable for medium- to large-sized networks - can take a long time to converge

Use of "hop count" as metric, creates two problems:

Limits the diameter of a RIP network to 15 router hops

Administrators cannot not use such factors as bandwidth and/or delay as the routing metric

Slow to flush unreachable destinations from the network, going through the "counting to infinity" procedure

Anyone can bring up a bogus RIP router, advertising bogus routes to disrupt routing (even though there is basic authentication in RIP v2)

Enhance Interior Gateway Routing Protocol

It is a advance distance vector routing protocol. This protocol stores the data of each router in three table that is routing table, topology table and neighbor table. Neighboring table stores the data of the neighboring router. Topology table contains the address of all the destinations in the network. For every destination address, both successor and a feasible successor are detected and save in the table if they exist. Routing table stores all the information of the routes from which the data is to be transferred. This protocol has been continued to be network-layer-protocol independent, and it allows DUAL to support other protocol suites. Updates are used to convey reach ability of each address. When a new neighbor comes in the network, then this protocol sends update packets to the new router or to new neighbor, so that it can build up its new topology table. For new neighbor update packets are unicast. In other cases, for example link cost change; update packets are multicast to the network. New updates are always transmitted reliably to the network.EIGRP does have summarization capabilities; it doesn’t make anybody think too much about the topology of the network, which again can get into trouble as the topology size increase. If any organization chooses OSPF at the starting because they are considering where their topology might be in five years, then they are aware enough to build an EIGRP topology that would also scale.

Configuration of Router 1C:\Users\user\Desktop\Untitled 23.png

router01>enable 

router01#configure terminal

router01(config)#interface fa0/0

router01(config-if)#ip address 172.16.0.1 255.255.0.0

router01(config-if)#no shutdownRouter01(config)#router eigrp 1

router01(config-router)#network 172.16.0.0

router01(config-router)#network 172.17.0.0

router01(config-router)#exit

router01(config)#exit

router01#

Configuration of router2

router02>enable 

router02#configure terminal

router02(config)#interface fa0/0

router02(config-if)#ip address 172.18.0.1 255.255.0.0

router02(config-if)#no shutdown

router02(config)#

router eigrp 1

router02(config-router)#network 172.17.0.0

router02(config-router)#network 172.18.0.0

router02(config-router)#network 172.19.0.0

router02(config-router)#exit

router02(config)#exit

router02#

 IGRP Protocol: - The full name of IGRP is interior gateway routing protocol and it also depend upon distance therefore it is also known as the distance-vector routing protocol, which means that every router in the network sends all or a some portion of its routing table as a routing message update at small interval of time to every neighbouring routers in the network. A router chooses the most appropriate path between a source of the data and a destination address. But at the same time each path can consists many links, then the system needs some way to compare those links in order to choose the best path. Rip has only one criteria to choose the best path that is hop count, but IGRP has five methods to determine the most suitable path and it depend upon the link speed of the source to destination, packet size, reliability and loading. Only network administrators can assign the weight age for each of these units. IGRP is a Cisco-proprietary distance vector protocol and it is designed to make it more scalable than RIP.

IGRP has the following distance vector characteristics:

• It sends routing updates in every 90 seconds.

• It sends out the full routing table every periodic update.

• It uses a form of distance as its metric (in this case, a composite of bandwidth and delay).

• It uses the Bellman-Ford distance vector algorithm to determine the more suitable path to a destination address.

IGRP uses bandwidth and delay in the Line, by default, to estimate its distance metric. Reliability, Load, and MTU, these are optional attributes that can be used to calculate the distance metric. IGRP must require an Autonomous System (AS) number in its configuration. Only routers in the same Autonomous system will send updates between each other. Following are the time constants in IGRP protocol:-

Broadcast time: - Here updates are broadcast by all gateways to the connected interfaces at that time. Updates are sends in every 90 seconds.

Invalid time: - If there are no update has been received for a given path in the network within specific time interval, then it is considered to have in dead lock condition or timed out. It should be several times the broadcast time, in order to allow for the possibility that packets containing an update could be dropped by the network. The default is 3 times the broadcast time.

Hold time: - When the router is unable to find the destination address or the metric has increased enough to cause a route poisoning, the destination goes into "hold down". At this state, no new path will be accepted for the same destination address for specific amount of time. The hold time indicates how long this state should last. It should be several times the broadcast time. The default value is 3 times the broadcast time plus 10 seconds. (As described in the Disable Hold downs section, it is possible to disable hold downs.)

Flush time: - If no update has been received for a given destination within this amount of time, the entry for it is removed from the routing table. Note the difference between invalid time and flush time: After the invalid time a path is timed out and removed. If there are no remaining paths to a destination, the destination is now unreachable. However, the database entry for the destination remains. It has to remain to enforce the holddown. After the flush time, the database entry is removed from the table. It should be somewhat longer than the invalid time plus the holddown time. The default is 7 times the broadcast time.

Configuration of IGRP in router 1

router01>enable 

router01#configure terminal

router01(config)#interface fa0/0

router01(config-if)#ip address 172.16.0.1 255.255.0.0

router01(config-if)#no shutdown

router01(config)# router igrp 1

router01(config-router)# network 172.16.0.0

router01(config-router)# network 172.17.0.0

router01(config-router)#exit

router01(config)#exit

router01#

Configuration of IGRP in router 2

router02>enable 

router02#configure terminal

router02(config)#interface fa0/0

router02(config-if)#ip address 172.18.0.1 255.255.0.0

router02(config-if)#no shutdown

router02(config)# router igrp 1

router02(config-router)# network 172.17.0.0

router02(config-router)# network 172.18.0.0

router02(config-router)# network 172.19.0.0

router02(config-router)#exit

router02(config)#exit

router02#

ISIS Protocol: - ISIS is intermediate system to intermediate system protocol and is designed to transfer the information more efficiently within the computer network. It did by selecting the best route for the data through packet switching network. IS-IS was made in 1992 in the recommendation of ISO/IEC. IS-IS was made for OSI routing and it is easily extendable. It is also called as"Integrated IS-IS"or "Dual IS-IS" and it is easy to be use for other protocols mainly IP version 6. Following is the IS-IS Operation: -

Send Hellos and build adjacencies

„ Create an LSP and flood it to eighbours

„ Receive all LSPs from eighbours

„ Run the SPF algorithm to calculate topology

„ Run PRC (Partial Route Calculation) to calculate IP routing info.

„ Newly received LSPs trigger SPF and/or PRC calculations

Strong Points of IS-IS over OSPF

Scalability

‹ Backbone is not an area, but the contiguous collection of

ABRs

„ Fast-Convergence

‹ IS-IS uses less packet types to propagate routing information

„ Easy-Troubleshooting

‹ All the prefixes are in single LSA packet. This helps tracing all routing information announced by a particular router

„ Less Resource Usage

‹ IS-IS databases contain one LSP per router in the routing domain

IS-IS Protocol Limitations

Metrics are 6 bits wide (0 to 63) : Default interface metric is 10 unless manually specified

„ All areas are stub areas : Might result in sub-optimal routing between areas

„ No filtering allowed : All ISs must have the same view of an area.

Use of summary-addresses for IP

Configuration of ISIS Protocol

Router A

router isis

net 49.0001.0000.0000.000a.00

interface ethernet 0

ip router isis

interface serial 0

ip router isis

Router B

router isis

net 49.0001.0000.0000.000b.00

interface ethernet 0

ip router isis

interface ethernet 1

ip router isis

interface serial 0

ip router isis

Configuration for Router C

router isis

net 49.0001.0000.0000.000c.00

interface ethernet 1

ip router isis

interface ethernet 2

ip router isis

IS-IS vs. OSPF

Common Points:

Both are internal gateway protocols (IGP) and used in the same autonomous system (AS);

Both are routing protocols based on the link status database, adopting SPF algorithm to calculate the route;

Both features fast convergence and no loop, applicable to large-scale networks;

Both adopt Hello protocol to form and maintain the neighbor relationship

Both use areas to form the two-layer hierarchical topology, both with the concept of Area

Both can aggregate the route between areas and support VLSM and CIDR, suitable for large-scale networks

Both elect DR on the broadcast network, and generate LSA (LSP) to describe the whole network segment

Both have the ability to verify the protocol packet

Differences:

The origin and design purpose of the protocol standard are different;

The enveloping modes of the protocol packet and the supported network protocols are different;

The relationship between the routers and areas and the organization modes of the link status database are different;

Definitions of the backbone areas are different;

The complexity of Hello protocol and requirement for the neighbor relationship establishment are different;

Aging modes of LSP (LSA) in the database are different;

DR election modes on the broadcast network are different;

Support capabilities to different models of the network types are different;

Distinguishing abilities to the metric of the link layer and the supported maximum metric are different.

BGP: - It is known as Border Gateway Routing Protocol. It is used to connect the different autonomous system. It performs the inter domain routing in Transmission Control Protocol/Internet Protocol (TCP/IP) networks. It is exterior gateway routing protocol and used to perform the routing between different autonomous system numbers. The hosts in BGP used Transmission Control Protocol to send the data between two router and they send the update of their routing table information only when any changr has been detected in the router. For this only changed part of the routing table is sent.

External & Internal BGP

BGP can have external or internal sessions

External BGP (E-BGP) session is used to exchange routing info between two speaker nodes in two different ASs

Internal BGP (I-BGP) session is used to exchange routing info between two routers inside an AS

Here are the steps to configure BGP on Cisco ROUTER

router# conf t

router(config)# router bgp 65501

router(config-bgp)# neighbor 10.10.10.2 

router(config-bgp-nbr)# remote-as 2000

router(config-bgp-nbr)# password <MD5 password>

router(config-bgp-nbr)# ebgp-multihop 2

routeR(config-bgp-nbr)# update-source loopback0

router(config-bgp-nbr)# address-family ipv4 unicast 

router(config-bgp-nbr-af)# route-policy xxxxx in 

router(config-bgp-nbr-af)# exit

router(config)#router static

router(config-static)#address-family ipv4 unicast

router(config-static-afi)#10.10.10.2/32 TenGigE0/1

router(config-static-afi)#commit

router(config)#

Basic configuration of in router 1&2

Router1#configuration terminal

Router1(config)#interface loopback 0

Router1(config-if)# ip address 42.42.42.1v255.255.255.0

Router1(config-if)# endhttp://evilrouters.net/wp-content/uploads/2008/11/mlppp.png

Router1

Here the configuration for router2

Router2#configuration terminal

Router2(config)#interface loopback 0

Router2(config-if)# ip address 69.69.69.1v255.255.255.0

Router2(config-if)# end

Router2

Here is the BGP configuration for Router 1

Router1# configuration terminal

Router1(config)# router bgp 42

Router1(config-router)# network 42.42.42.0 mask 255.255.255.0

Router1(config-router)# neighbour 192.168.42.2 remote-as 69

Router1(config-router)#end

Router1#

Here is the BGP configuration for Router 2

Router2# configuration terminal

Router2(config)# router bgp 69

Router2(config-router)# network 69.69.69.0 mask 255.255.255.0

Router2(config-router)# neighbour 192.168.42.1 remote-as 42

Router2(config-router)#end

Router2#