Enhanced Analysis on Route Summarization and Route … · Enhanced Analysis on Route Summarization...

Enhanced Analysis on Route Summarization and Route

Redistribution with OSPF vs. EIGRP Protocols Using

GNS-3 Simulation.

Haresh N. Patel, Prof.Rashmi Pandey Department of Electronics

& Communication Engineering Vedica Institute of Technology, Bhopal

ABSTRACT

Routing protocol is taking an important role within

the Different internet era. A routing protocol

determines however the Routers communicate with

one another to forward the packets by taking the best

path to travel from a source node to a destination

node. During this paper we've explored two eminent

protocols specifically, Enhanced Interior Gateway

Routing Protocol (EIGRP) and Open Shortest Path

First (OSPF) protocols based on route redistribution

and route summarization using different techniques

to reduce routes, filter LSA Types and also reduce

size of LSA database, traffic of networks. In any

case, having a multiple protocol atmosphere makes

redistribution a necessity. Variations in routing

protocol characteristics, like metrics, administrative

distance, classful and classless capabilities will result

route redistribution. Though should be to those

variations for distribution to succeed. Then traffic of

the network is increase. This analysis will simulate

Networks using Route summarization, Stub area,

Totally Stub area , NSSA area, NSSA stub area

,NSSA totally Stub Area, Additionally greatly

reduces processor workloads, memory and

information measure demand. Index Terms

OSPF, EIGRP, Route Summarization, Route

Redistribution, Stub Area, Totally Stub area, NSSA

area, NSSA- Stub Area, NSSA-Totally Stub Area.

1. A BRIEF LOOK ON ROUTE

SUMMARIZATION:

In Internet networking terminology, Supernet is a

block of contiguous subnet works addressed as one

single subnet within the larger network. Supernets

perpetually have a subnet mask that's smaller than

the masks of the component networks.[1] The size of

routing tables has been rapidly increasing during the

expansion of the Internet. Route summarization

is the process of aggregating routes to multiple

smaller networks that saving storage space in the

routing table and simplifying routing decisions.

Routes advertisements to neighboring gateways are

reduced. Route summarization within large and

complex networks can isolate topology changes from

other routers. This can improving the stability of the

network by limiting the propagation of routing traffic

after a network link fails. Example such as if a router

only advertises a summary route to the next router

then it does not advertise any changes to specific

subnets in the summarized range. This can reduce

any unnecessary routing updates following a

topology change. Hence that increases the speed of

convergence and allows for a more stable

environment.[2][3]

In it is most basic form; route summarization

is the taking of multiple route entries and

representing them by a smaller number of entries.

This allows you to reduce the memory requirements

on a router, thereby improving performance. But in

order to use route summarization proper effectively,

you must implement an effective hierarchical

addressing scheme that which can have a found

impact on the performance and scalability of your

network. One of the biggest benefits of route

summarization is the shrinking of the routing table,

which results in the reduced amount of memory

used. This also results in a router spending less time

looking for a route in its routing table and also

results in having a smaller link-state database and

making the process of the SPF algorithm better.

Summarization also reduces the number of routing

updates sent because of link or network flaps. That

Haresh N Patel et al, Int.J.Computer Technology & Applications,Vol 5 (5),1682-1689

IJCTA | Sept-Oct 2014 Available [email protected]

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by summarizing networks, you in effect isolate all

the flapping but it does have the disadvantage of

other routers still sending data to the router that is

advertising the summarized network.

Troubleshooting will be easier with summarization

configured since you are better able to isolate the

part of your network where issues may arise. One

drawback to be aware of with summarization is the

lost of routing information. Which can result in sub-

optimal routing if a network within the summarized

route were to go down. Assigning subnets according

to simple octet or bit boundaries allows you to make

addressing and summarization easier to accomplish.

Placing subnets in blocks that are a power of 2 also

helps optimize summarization.

2. OSPF ROUTE SUMMARIZATION

Area border routers (ABRs) send summary link

advertisements to describe the routes to other areas.

It is depending on the number of destinations and an

area can get flooded with a large number of link-state

records. This can utilize routing device resources to

minimize the number of advertisements that are

flooded into an area. You can configure the ABR to

combine or summarize a range of IP addresses and

send reachbility information about these addresses in

a single link-state advertisement (LSA). You can

summarize one or more ranges of addresses where all

routes that match the specified area range are filtered

at the area boundary and the summary is advertised

in their place.[1][2]

For an OSPF area, you can summarize and filter

inter-area prefixes. All routes that match the

specified area range are filtered at the area boundary

and the summary is advertised in their place. For an

OSPF not-so-stubby area (NSSA), you can only filter

NSSA external (Type 7) LSAs before they are

translated into AS external (Type 5) LSAs and enter

the backbone area after all external routes learned

within the area that do not fall into the range of one

of the prefixes are advertised individually to other

areas.

3. EIGRP AUTOMATIC & MANUAL

SUMMARIZATION

By default EIGRP has auto summarization enabled.

This means that it will summarize to class full

addresses at network boundaries. Leaving auto

summarization enabled can cause a lot of troubles

occur in the network. EIGRP has the ability to create

summary routes at random boundaries by using

manual route summarization. Manual route

summarization can be applied anywhere in EIGRP

domain, on every router and on every interface.

Summary route will live in routing table as long as at

least one more specific route will exist.

If you want to use auto route summarization

you have to do nothing because it is enabled by

default, otherwise use no auto-summary EIGRP

command to disable it. To do manual route

summarization go to on interface and use { ip

summary-address eigrp as-number address mask

[administrative-distance] } command.[3][4]

4. OSPF AND EIGRP ROUTE

REDISTRIBUTION

Mutual route redistribution is the process where two

dynamic routing protocols exchange their routes with

each other. Example such as when you route

redistribute EIGRP into OSPF then all routes in the

EIGRP Autonomous system will be in the OSPF

database that show up as OSPF routes in the OSPF

domain. Same with EIGRP when you redistribute

OSPF into EIGRP then all the routes from OSPF will

be carried over to EIGRP and advertised throughout

the autonomous system.

Mutual route redistribution is a common when

companies acquire other companies that use different

routing protocols. In such case Company XYZ Inc.

acquires Company ABC Inc. however XYZ Inc. uses

OSPF and ABC Inc. uses EIGRP. After the

acquisition, the Chief Technology Officer mandates

that there be full network communication between

the newly merged companies. In this case you need

to perform mutual redistribution to ensure XYZ Inc.

has routes to ABC‟s network and vice-versa.

5. PROPOSED METHODOLOGY

5.1 Route Summarization 5.1.1 Using Route Summarization to reduce the

size of routing table:

Route summarization offers many vital advantages

over flat routing. Route summarization can reduce

the latency in a complex network, when many

routers are involved in the networks. It will also

reduced number of routing entries, the overhead for

routing protocols is reduced. Network stability will

be improved by reducing or eliminating unnecessary



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routing updates after part of the network undergoes a

change in topology. Route summarization also

reduces processor workloads, memory necessities

and bandwidth demand.

A Different AS with a large number of networks,

OSPF router should keep the LSA of every other

router in its LSDB. Every router in a large OSPF AS

has a large LSDB. The SPF calculation of a LSDB

can require a substantial amount of processing. Also,

the resulting routing table will be large, containing a

route to each network in the AS. In an effort to

reduce the size of the LSDB and the process

overhead for the SPF tree and routing table

calculation, OSPF permits the AS to be divided up

into groups of networks called areas.

5.1.2 Using Stub Area to filter LSA Type 5 and to

reduce size of routing table:

Does not accept information about external to the

AS. If routers need to route to networks outsides an

AS, They will use a defaults route (0.0.0.0).This kind

of area reduces the size of link state database, and

result of that it will reduces the memory requirement

of the routers inside that area. External networks

LSA type 5s are not allowed to be flooded into a stub

area, to get to external route networks, routers will

use the default route.

5.1.3 Using Totally Stubby Area to filter LSA

Type 3, 4, 5 and reduce size of routing table:

Does not accept external AS route, or summary

routes from other areas internal to the AS. A defaults

route is injected for reachbility to other networks

outside that area. Cisco Proprietary solution. It can

only be used if all the routers are CISCO.

Flooded LSAs are: LSA type1, and LSA type2.

5.1.4 Using Not So Stubby Area (NSSA Area) to

allows LSA Type 1, 2, 3, and 7:

Many service providers have OSPF areas that they

have only one exit point, but the areas consist an

ASBR

Solution: Not-So-Stubby Areas (NSSAs) .The

ASBR originates a Type 7 LSA. The ABR converts

from Type 7 to Type 5. It‟s Hybrid Stub area that can

accept external route with using LSA type 7s. LSA

Type 7s can be originated and advertised throughout

a NSSA.

LSA Type 7s then will be translated in to LSA Type

5s by the ABR and flood in to the area 0. NSSA can

only receive the LSA Types 1, 2, 3 and 7. Prior to

NSSA, if an area had external route, that area could

not be set to STUB of any Kind.

5.1.5 Using NSSA Stub Area to advertise a default

route manually:

By default, stub ABRs are advertise a default route.

By default, NSSA ABRs don't. To force NSSA to advertise a default route.

5.1.6 Using NSSA Totally Stub Area to reduce

size of routing table to filter LSA Type 7:

After you define the NSSA totally stub area, Area

has these characteristics in addition to the NSSA

characteristics: No type 3 or 4 summary LSAs are

allowed in Area. This means no inter-area routes are

allowed in Area. A default route is injected into the

NSSA totally stub area as a type 3 summary LSA.

5.2 Route redistribution: The use of a routing protocol to advertise routes that

they are learned by another routing protocol such as

static routes or directly connected routes is called

redistribution. Whereas running one routing protocol

throughout your entire IP internetwork is desirable,

multi-protocol routing is common for variety of

reasons, such as company mergers, multiple

departments managed by multiple network

administrators and multi-vendor environments.

One-Point redistribution defines one redistribution

point between two routing protocols. By this we

mean routes redistributed on only one router. The

distribution can be: [A] One-way [B] Two-way. One-

way route redistribution requires the use of a default

route or static routes. Here Experimental Analysis in

first lab identify one way route redistribution. Two-

way route redistribution when performed on two or

more separate routers both running routing protocols.

Here Experimental Analysis in second lab identify

two way route redistribution.

6. SIMULATION

GNS3 is a Graphical Network Simulator that allows

emulation of complex networks. You familiar about

with Virtual Box or Virtual PC, VMWare that are

used to emulate various operating systems in a

virtual environment. This software is used to emulate

Cisco ASA and Cisco IPS, PIX firewalls, Juniper

routers as well as hosts Like Linux, Windows, Mac

OS X, FreeBSD etc.

Simulation is performed using GNS3 software. In

this paper, there are 4 typologies to be simulated

based on route redistribution, route Summarization,

OSPF Stub and NSSA Area. Each topology consists

of four routers and each router is connected to

several computers through network switch. Each

network topology simulated using IPv4 addressing

mode with OSPF and EIGRP Protocols.

In the first topology, each router is connected to

other router through network switches and devices.

This topology is also called multi-access network.

To perform Static Vs Defaults Vs OSPF and

Injecting Default Route with Route Redistribution

using OSPF Routing Protocol.

In Figure 1: R1 is Acting as the ISP and R2 is the

Edge router for company that is running OSPF

internally R2, R3, R4 .R1 will have static route

towards all the company networks. R2 will have



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default route pointing toward R1.R2 should inject the

default route in to R3 and R4.

In Figure 2: Performing Mutual redistribution

between EIGRP and OSPF. Run EIGRP between R1

and R2.Run OSPF between R2, R3 and R4.Also

Both Protocols have different Autonomous System.

In figure 3: configure OSPF in Multi-area

configuration based on the network diagram.

Advertise all the loopbacks on all the routers. Verify

the different types of routes in a Multi-area

configuration. Perform Route summarization such

that all the loopbacks from Area 10 and Area 100 are

summarized.

After Route Summarization, Configuration of

Stub area and totally stub area build on this

topology. Here loopback advertise using

redistribution and to filter LSA type 3, 4, 5.

Figure 1: Injecting Default Route using OSPF

Protocol.

Figure 2: Route redistribution between OSPF vs.

EIGRP with Different Autonomous System.

Figure 3: Multi-Area Connection Using Route

Summarization.



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Figure 4: Configuring Not-So-Stubby Area

In figure 4: configure OSPF in Multi- area

configuration based on the network diagram.

Configure Area 10 as a NSSA Area to prevent

External routes from the backbone getting

injected into it. Make sure that everybody

outside of Area 10 has reachbility to external

routes injected by the ASBR in Area 10.

In Configure Area 10 a NSSA-Stub to

maintain reachbility to the external routes from

the Backbone. In Configure Area 10 as a NSSA-

Totally area to block the Inter-area routes as

well from getting injected into area 10.

7. ANALYSIS

After Analysis of Topology 1(figure-1).we can

see injecting default route (Routing table 7.3)

With route redistribution. Advertising route

from Source Router R1 to Destination Router

R2.

Analysis of Topology 2 (figure -2) identify

Route redistribution between OSPF and EIGRP

with different AS. We can see in the routing

table 7.4 injected External routes of R3 and R4

Using route redistribution.

Analysis of Topology 3(Figure-3) identifies

Route Summarization with OSPF multi area

connection. After summarization we can see

Reduce size of routing table. (Routing table 7.5)

Routing table 7.6 indentify configuration of

Stub area and to filter LSA Type 5.more reduce

size of routing table. Routing table 7.7 identify

configuration of Totally Stub area and to filter

LSA type 3, 4, and 5. Furthermore reduce size

of routing table. We can see route on routing

table.

Analysis of Topology 4(Figure-4) identifies

Configuration of NSSA Area. (Routing table

7.8) NSSA Area does not provide default route

so we can manually configure default route

using NSSA Stub area. After filter LSA type 7

using NSSA Totally Stub area.

Routing Table 7.1- of Router R1 (Figure -1)

Routing Table 7.2- of Router R4 (Figure -1)



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Routing table 7.3 – of Router R2 (Figure -1)

Routing table 7.4 – of Router R4 (Figure -2)

Routing table 7.5 – of Router R4 (Figure -3) – After route Summarization



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Routing table 7.6 – of Router R4 (Figure -3) – After Configured STUB Area.

Routing table 7.7 – of Router R4 (Figure -3) – After Configured Totally STUB Area.

Routing table 7.8 – of Router R2 (Figure -4) – After Configured NSSA Area.



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8. CONCLUSION

In this paper, performance analysis based on

route summarization and route redistribution

using OSPF and EIGRP protocols. Which may

be achieved that shown within simulation result

and routing table analysis. Finally, Reduces the

amount of information stored in routing tables,

also reduce CPU and Memory utilization of

networks. To makes the routing process more

efficient. To reduce the network convergence

time

Reduced Frequency of SPF calculation:

detailed routing information is kept within each

area so it‟s not necessary to flood all Link-state

changes to all other areas, thus not all routers

need to run the SPF calculations.

Smaller Routing Table: Because detailed

routing information is kept within an area, the

routers within an area will have smaller routing

table.

Reduced Link-state Updates: LSU is can

contain a variety of LSA types, instead of

sending an LSU about each network within an

area, you can advertise a single or fewer

summarized routes between areas to reduce

overhead associated with LSU.

9. ACKNOWLEDGEMENTS

I would like to sincere thanks to their family

members and their Guide, Principal and

Director, HOD of Electronics and

Communication department of Vedica Institute

of Technology (VIT), Bhopal for encouraging us

for this research work.

10. REFERENCES

[1] "CCNP ROUTE 642-902 Official

Certification Guide, by Wendell Odom" 2014

[2] CCNA Routing and Switching Study Guide:

Exam 100-101, 200-101, 200-120 (15 Oct 2013).

[3] TODD LAMMLE (AUTHOR), CCNA ROUTING

AND SWITCHING STUDY GUID, 2013

[4] Alex A. Stewart and Marta F. Antoszkiewicz,

“Route Analysis and Management System”,

2009.

[5] Franck Le,” Understanding Routing

Redistribution”, International conference,

Beijing, China, 2008.

[6] W.T.Zaumen and J.J. Garcia-Luna-Aceves,

Dynamics of Link-State and Loop-Free Distance-

Vector Routing Algorithms," Journal of

Internetworking, Wiley, Vol. pp. 161-188, 3rd

December 1992

[7] J.J. Garcia-Luna-Aceves,„Method and Apparatus

for Distributed Loop-Free Routing in Computer

Networks,„U.S. Patent application, SRI

International, Menlo Park, California, 1993

[8] Bob Albrightson , J.J. Garcia-Luna-

Aceves,Joanne Boyle.,3rd March,„EIGRP routing

protocol based on distance vectors„, Journal of

internetworking ,Wiley,Vol pp 200- 205, 2001.



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