Regarding tunnels

[ncnaveen_arasu]

Hi coluld any one please share the knowledge on what are tunnels and why do we use. How many diffrent types of tunnels exist and when do we use those specific tunnels.

Thanks in advance,

Naveen

[Joseph W. Doherty]

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Posting

Generally, they support a virtual link between the tunnel end points.

Why they are used is for some reason the underlying physical path can't be used for some purpose.

A couple of examples: you want to link two of your business sites internal networks together across the Internet.  You might create a tunnel link between two of your routers across the Internet.  Your internal network "sees" a link between those routers logically like a direct link between those two routers.  They "do not see" the Internet.

You have a private WAN link between two of your sites, but the information is extremely sensitive.  You define an encrypted tunnel across the link and transmit your data through it.  Again, your network just "sees" a link between the two sites, but if anyone can tap you physical link, the contents are secured by encryption.

Unsure of how many types exist but most you're likely to encounter are probably some variant of GRE or IPSec encapsulated tunnels.

[Muhammad Thanveer]

Dear Naveen,

Please find the info as below:

what are tunnels:

Tunneling is the process of placing an entire packet within another packet(encapsulation) before it's transported over the Internet

why do we use:

The purpose of the tunneling protocol is to add a layer of security that protects each packet on its journey over the Internet

How many diffrent types of tunnels exist and when do we use those specific tunnels.

for more info you please go through the link below:

http://www.cisco.com/en/US/docs/ios/12_4/interface/configuration/guide/inb_tun.html#wp1045623

Tunnels are used by many different technologies to solve different network challenges, and the resulting variety of tunnel types makes it difficult to determine which tunneling technique to use. The different carrier protocols can be grouped according to the OSI layer model.

Table 1

shows the different carrier protocols grouped by OSI layer. Below the table, each carrier protocol is defined, and if the tunnel configuration is not covered within this module, a link to the appropriate module is included.

Table 1 Carrier Protocol by OSI Layer

Layer	Carrier Protocol
2	•PPPoA—Point-to-Point Protocol (PPP) over ATM •PPPoE—PPP over Ethernet •UDLR—Unidirectional link routing
3	•BSTUN—Block Serial Tunneling •CLNS—Connectionless Network Service (CLNS) •GRE—Generic routing encapsulation •IP-in-IP—Internet Protocol encapsulated within IP •IPSec—IP Security •IPv6—IP version 6 •L2F—Layer 2 Forwarding •L2TP—Layer 2 Tunneling Protocol •MPLS—Multiprotocol Label Switching •PPTP—Point-to-Point Tunneling Protocol •STUN—Serial Tunneling
4	•DLSw+—Data-link switching plus •RBSCP—Rate-Based Satellite Control Protocol •SSL—Secure Socket Layer

Please rate the helpful posts.

Regards
Thanveer
"Everybody is genius. But if you judge a fish by its ability to climb a tree, it will live its whole life believing that it is a stupid."

[shillings]

Sometimes it's useful to encapsulate one tunnel in another. For example, IPsec tunnels don't support multicasts. This will pevent a routing protocol working, such as OSPF. However, GRE does support multicasts so traffic can first be encapsulated within a GRE tunnel before IPsec encapsulation.

[Muhammad Thanveer]

Key point Shillings, Thanks good info given.

Regards
Thanveer
"Everybody is genius. But if you judge a fish by its ability to climb a tree, it will live its whole life believing that it is a stupid."