Vpn Command Line Interface Configuration Using Packet Information Technology Essay


This paper clearly examines and explains Virtual Private Network ( VPN ) , its operation, benefits and describes the process to put up a Site-to-site Virtual private web utilizing bid line interface. IPSec VPN is employed and the execution is carried out utilizing the package tracer.


Let us foremost depict a Private Network. Private web consists of computing machines owned by one organisation which portion information peculiarly with each other.

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Virtual Private Network provides an efficient, dependable, secured and user friendly method of communicating and informations going over VPN. Data transmitted over VPN is secured by utilizing encapsulation, encoding, hallmark, utilizing firewalls or by supplying security mechanism utilizing burrowing protocols. Virtual Private Network is used for picture conferencing, file sharing and distant entree.


Suppose, if the company has Local Area Networks in its caput office at London and other Local Area Networks in the subdivision office at Manchester, by implementing VPN, informations and resource sharing will be economic, dependable, and fast and provides security by utilizing

The undermentioned constellation is an illustration of a VPN.

Figure 1: Example of a VPN [ 3 ]

Why construct a Virtual Private Network?

Earlier, companies used leased phone lines to pass on between its subdivision offices. Leased lines ( dedicated lines ) offered security, privateness and connexion was available at any clip. However, leased phones were expensive and unreasonably high when companies ‘ subdivision offices were spread over across a state. As the popularity of Internet grew, companies started to deploy more computing machines for resource sharing. In order to keep the privateness and unity many companies started to make their ain Virtual Private Networks ( VPNs ) to complect the distant subdivision offices and cater the demands of distant employees. Over the old ages, demand for VPN began to turn as it provides a cost-efficient solution for big administrations to firmly reassign informations between its subdivision offices.

Using VPN we can make a secure, private web over a public web. It makes usage of practical connexions ( impermanent connexions ) to link a individual computing machine and a web, two computing machines or two webs [ 1 ] .

VPNs are chiefly used to accomplish the undermentioned ends [ 2 ] :

aˆ? Provide remote entree firmly to a corporate web

aˆ? Interconnect subdivision offices to an endeavor web ( intranet )

aˆ? Expand companies ‘ bing calculating substructure to include spouses, providers and clients ( extranet ) .

Benefits of utilizing VPN

In order to supply fast, dependable and secured method of conveying the information over two users or webs, VPNs are used. Security being the major concern, VPN provides an economic solution to firmly reassign informations and protects unity of companies ‘ resources and confidential informations.

Cost Salvaging

Network Scalability

Cost Economy: Exploitation VPNs, the cost of keeping waiters is reduced and companies can use third-party services and outsource their support. This minimizes the organisations ‘ outgo through resource sharing and facilitates services to many concern clients.

Network Scalability: Cost of constructing a private web bit by bit increases as the organisation expands. An organisation with several subdivision offices can be connected utilizing Internet based VPN, thereby avoiding scalability job. Internet based VPNs use public lines to link remote and distant locations across a broad geographical country. It offers secure, dependable connexion and quality of service. [ 4 ]

Types of VPN [ 7 ] .

Three basic types of VPN

Remote Access



Remote Access VPNs

They provide unafraid connexions chiefly for distant entree users and offer same degree of security as private webs. With the assistance of Remote Access VPNs, remote users will be able to entree informations at companies ‘ caput office from any subdivision offices. Remote entree VPNs are employed in big organisations. It offers secure, dependable and encrypted connexion across a public web. [ 3 ]

Fig 4 shows distant entree VPN

Fig 4 Remote entree VPN

Site-to-site VPNs

It uses greater encoding methods where an organisation can link many sites on a public medium.

Sitea?’toa?’site VPNs can be classified into Intranets or Extranets.

Intranet VPNs

Intranet VPNs are largely used to link structured webs which may distribute over a big geographical country. They may be used to link companies ‘ caput offices, distant offices and subdivision offices utilizing private lines. They are besides used to link within an organisation. They offer dependable connexion. It gives greater flexibleness to implement coveted security degrees in an organisation. Intranet VPNs provide same degree of security and connectivity as private webs. [ 7 ]

Figure 2 shows an intranet VPN topology

Figure 2

Extranet VPNs

Extranet VPNs are used to link companies ‘ Intranet over a shared substructure utilizing dedicated lines. They connect broad scope of users. They offer greater user rights to telecommuters and distant offices.

Figure 3 is an illustration of Extranet VPN

Figure 3

Analysis of current VPN engineerings

The different VPN engineerings are as follows





IPSec consist of a set of specific protocols and techniques which are required to put up unafraid Virtual Private Network connexions. Internet protocol ( IP ) packages may be altered during the transmittal which does non supply informations security. By implementing IPSec transmittal security may be achieved while conveying IP packages. IPSec uses hallmark, cheques for package dependability and encapsulates in order to guarantee informations security. IPSec may be used as a tunnelling protocol and finds application for site-to-site VPNs.

Internet cardinal exchange protocol ( IKE ) is used to set up an IPSec connexion. It is a protocol which is used to interchange IPSec parametric quantities and helps to develop security associations ( SA ) between two terminal devices. A security association ( SA ) is created when understanding of IPSec parametric quantities occur between the terminal devices. IKE uses two protocols




There are two types of IPSec connexions

Transport manner

Tunnel manner

Transport manner

In this manner, IPSec heading information is added to the IP heading which contains hallmark and encapsulation information. It uses hashing mechanism to code the warhead part of the IP package.

Tunnel manner

It provides more options as packages may be encrypted or encapsulated.

It is used for distant entree. [ 6 ]


The bed two burrowing protocol was developed jointly by Cisco and Microsoft. It is chiefly used for distant entree. [ 3 ] It can besides be used for non-IP webs. Encapsulation is done on an full Ethernet frame into UDP packages. Packages incorporating local web references may be transmitted through the public medium. In order to guarantee security and privateness, an IPSec heading information is added to the L2TP heading. [ 6 ]


Point-to-Point Tunnelling Protocol ( PPTP ) was created by Microsoft. It is one of the most widely used VPN methods. As PPTP does non supply informations encoding, Microsoft Point-to-Point Encryption ( MPPE ) protocol is used. PPTP combined with MPPE protocol provides security and one of the fastest VPN methods. [ 3 ]

Issues caused by VPN [ 12 ]

There are four common types of jobs which may go on with VPN connexions. These are:

The VPN connexion being refused.

Accepting untrusty connexion.

The inability to make locations that lie beyond the VPN waiter.

Failure of tunnel creative activity.

Future of VPN

VPN is going more popular with more companies deploying VPN for distant entree. This will be an economic agencies and provides distant entree for employees in an organisation.

Execution of Site-to-site VPN [ 9 ]

The execution of Site-to-Site IPSec VPN utilizing bid line interface is carried out in the Packet Tracer 5.2 plan.

The topology for the Site-to-Site web is shown in Fig [ 4 ] below [ 9 ]

Fig [ 4 ]

The above topology consists of three routers R1, R2 and R3. The aim is to put up a site-to-site VPN entree between Site 1 and Site 2. The web dwelling of PC-A, Switch0 and Router 1 forms the Site1 and likewise web dwelling of Router 3, Switch1 and PC-C forms the Site 2. The IPSec VPN tunnel is created between the Router 1 and Router 3. Router 2 merely bypasses the interesting traffic and does hold any function of supplying VPN. IPSec is responsible for supplying protection when conveying private information over public webs such as Internet. It protects and authenticates IP packages supplying informations security.

There are five stairss in developing an IPSec VPN [ 13 ]

Measure 1: Identifying interesting traffic utilizing access-list and originating VPN connexion

Interesting traffic refers to the traffic which is encrypted. For site1, all traffic that flows between Router 1 and Router 3 ( Fig 4 ) is encrypted. Interesting traffic is being created between the beginning web and finish web with references and severally. Similarly, we need to make interesting traffic for site2 where the beginning web reference and finish web reference will be and severally. Any other traffic which flows across the web will non be encrypted.

In the above execution, entree list has been configured with the value 110 to categorise the traffic from web on router 1 to the web on router 3 as interesting.

In order to originate the VPN connexion, traffic demands to be generated between the routers R1 and R3.

Measure 2: Establishing IKE Phase 1

IKE Phase 1 is mandatory where security association is created. ISAKMP key is being used. Two manner security associations are established between the equals in this stage. Data traveling over the devices uses the same key. In this stage, equal hallmark occurs [ 11 ] .

Measure 3: Establishing IKE Phase 2

The existent IPSec tunnel is established in this stage. IKE phase 1 generates unafraid communicating nexus between Router1 and Router3 ( Fig 4 ) and IPSec tunnels are created for coding informations. IPSec connexion between two terminal devices requires two security associations [ 11 ] .

The undermentioned maps are performed in IKE Phase 2:

Pull offing IPSec security parametric quantities

Establishing IPSec Security Association

Periodic regeneration of IPSec security associations to guarantee informations security

Extra Diffie-Hellman ( DH ) exchange

Measure 4: Secure transmittal of informations

After the completion of IKE stage 2, interesting ( encrypted ) traffic flows through IPSec tunnel and is delivered to the end point.

If a “ Ping ” bid is issued on the Router1 ‘s Loopback interface, it is sent to the Router3 ‘s loopback interface. Router1 is responsible for get downing the IKE stage 1. After the successful completion of IKE stage 1, it initiates phase 2. After completion of IKE stage 2, interesting ( encrypted ) traffic is transmitted over the IPSec tunnel.

Measure 5: Verifying the IPSec VPN tunnel and tunnel expiration

The show crypto isakmp SA bid is issued to see the current active IKE SAs. “ Active ” position indicates that ISAKMP Security Association is in active province.

The Source IP reference indicates the starting point which started the IKE dialogue. The QM_IDLE manner indicates Quick Mode exchange and the IPSec Security Association remains authenticated.

The show crypto ipsec SA bid is used to demo the current security association ( SA ) scenes. It displays reference of local host and distant hosts. It shows current equal which is set.

If we issue demo crypto ipsec SA bid before pinging the PC-C from PC-A, we find that Numberss of packages encapsulated, encrypted, decrypted and de-capsulated are all zero. This is because no traffic is generated between the Router1 and Router3. In order to verify the IPSec tunnel, we need to ping the PC-C from PC-A or frailty versa. After a successful Ping and reprinting the above bid, we find that Numberss of packages encapsulated, encrypted, decrypted and de-capsulated are all more than zero which indicates that IPSec tunnel is active and is coding the information.

After the SA Lifetime timer expires, the tunnel is shut down. It is besides possible to manually cancel an IPSec tunnel.

The show crypto ipsec security-association life-time bid is used to see the Security Association ( SA ) Lifetime.

Summary and Conclusion

Virtual private webs provide effectual security and dependability for conveying confidential informations over the Internet. It is a cost effectual method for linking the organisations ‘ subdivision offices and helps to supply distant entree for employees within an organisation. It is suited for big organisations and helps in sharing and using the resources of an organisation efficaciously. Virtual private webs provide secure, dependable and fast entree across the Local country webs and Wide Area Networks ; and offer a good alternate solution to companies ‘ expensive leased lines.