Tunneling technology

[contactyk]

Hi all,

I am a newbie to VPNs .so plz bear with me.I want to know when we r using GRE over IPSEC? If i am not wrong GRE are not secure as compared to IPSEC. If we want secured tunnels we can use IPSEC but in GRE over IPSEC wht is use of GRE tunnels? As per my knowledge(very litttle) IPSec tunnels r in bet peers while GRE tunnels formed bet logical tunnel interfaces.If in IPSEc peer-to-peer secured tunnels r getting fomred then whts use of GRE in that?

[mhussein]

As you mentioned, GRE supports encryption but it is not a secure tunneling/encapsulation protocol.

At the same time there are limitations to IPSec: it can not carry non IP protocols such as IPX and AppleTalk. IPSec tunnels also can not normally forward routing protocol traffic such as OSPF and EIGRP. That is why -I think- most IPSec configurations are referred to as LAN-to-LAN (using static routes for each SA).

In a nutshell, use GRE with IPSec if you are routing IPX/AppleTalk or if you have two routers that need to exchange routing PDU's through the tunnel.

Configuration Example:

http://www.cisco.com/en/US/tech/tk583/tk372/technologies_configuration_example09186a0080093f85.shtml

Regards,

Mustafa