Tunnel modes !

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Sep 15th, 2008
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Hi all, Can someone kindly explain me the main difference between tunnel mode gre and ipnip. in our environmnet, when we try to form tunnel interfaces, usually they work fine with gre but sometimes we need to use ipnip without any obvious reason, so i need to understand why this is happening, if some1 could refer me a doc or article, explaining the usage of both of them in different scenarios will be very helpful.


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Edison Ortiz Mon, 09/15/2008 - 17:29
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GRE allows you to transport non-IP protocols via the tunnel (IPX, AppleTalk) while IPnIP allwows you to transport IP Only protocols, as the name implies.

GRE adds a header which increases the size of the packet hence causing fragmentation.

It also uses a different protocol (Protocol 47) vs (Protocol 41) used by IPnIP. If you are having problems establishing the tunnel, it may be due to Protocol 47 being blocked while Protocol 41 is allowed.

What problems have you encountered?




ropethic Mon, 09/15/2008 - 17:41
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RFC2003 and RFC2004 - Tunnel encapsulation


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