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ip sec tunnels

Unanswered Question
Jan 24th, 2008
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Hi all

I know ip sec is a encryption protocol used for vpn. but what tunneling method does it use ? ie you can have lt2p over ipsec, l2tp is the tunneling protocol. with a normal ipsec tunnel, what creates the tunnel ? or is there not a tunnel, just encrypted traffic ?

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senthil_kumarpv Thu, 01/24/2008 - 04:32
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When IPSec tunnel mode is used, IPSec encrypts the IP header and the payload, whereas transport mode only encrypts the IP payload. Tunnel mode provides the protection of an entire IP packet by treating it as an AH or ESP payload. With tunnel mode, an entire IP packet is encapsulated with an AH or ESP header and an additional IP header. The IP addresses of the outer IP header are the tunnel endpoints, and the IP addresses of the encapsulated IP header are the ultimate source and destination addresses.

IPSec tunnel mode is useful for protecting traffic between different networks, when traffic must pass through an intermediate, untrusted network. Tunnel mode is primarily used for interoperability with gateways, or end-systems that do not support L2TP/IPSec or PPTP connections. You can use tunnel mode in the following configurations:

• Gateway-to-gateway

• Server-to-gateway

• Server-to-server


Senthil Kumar P V


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