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MohamedCSE

two gre tunnels using same source

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is it possible to have two gre tunnels using same source but each tunnel has it's own destination??

Edited by MohamedCSE
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When it comes to cisco here is what cisco says:

 

You cannot have two tunnels using the same encapsulation mode with exactly the same source and destination address. The workaround is to create a loopback interface and source packets off of the loopback interface.

 

Here is the link on how to use loopback to achieve this: http://www.cisco.com/en/US/docs/ios/interface/command/reference/ir_t2.html#wp1012689

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But isn't this the case when 2 tunnels have both the source and the destination addresses the same? I thought that having only the source address in common is not an issue. Please correct me if I am wrong.

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But isn't this the case when 2 tunnels have both the source and the destination addresses the same? I thought that having only the source address in common is not an issue. Please correct me if I am wrong.

 

 

Yup that would work. Source and destination can not be the same for two tunnels.

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Hi Mohamed,

 

The answer to your question is straightforward, YES you can have hunderd tunnels with same source but different destinations. Its a very common practice, specially in HUB and SPOKE designs.

 

Now, a question arises, can we have 2 tunnels with exact same source and destination ? Then again the answer is YES. You can have multiple tunnels with exact same source and destination without using any loopback techinques.

 

Although having 2 tunnels with same source/destination makes sense in some very absurd cases but to keep the facts straight, just remember that its possible, although you might need some extra config to make both tunnels work in the way you want.

 

Let me know if anyone is interested in knowing how it works :-)

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Hello Pappyaar,

 

As i was reading one of your old posts the way that you can have 2 or more tunnels with same source & destination is by adding Tunnel Key <key_name> for all tunnels , correct?

 

Another question - Can we have both GRE & IPSEC tunnels with this scenario?

 

Thanks in advance. I have been reading your other posts as well and the way you explain the concept is great. Even novice like me was able to try tclsh. :)

 

Regards,

HS.

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Its also possible with Multipoint GRE (mGRE) to ease administration from the hub side of things particularly when you have remote access users. Here is a pretty good configuration document:

 

http://cciethebeginning.wordpress.com/2008/06/29/gre-generic-routing-encapsulation-point-to-point-multipoint-gre/

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Hi,

 

I would like to ask help for this setup.

 

The scenario is like this.

 

RtrA = 1xcircuit (f0/0) 163.81.217.138

RtrB=2xcircuit (f0/0 163.81.217.122), (f0/1 159.42.205.242)

 

This is using GRE with IPSEC.

From RtrB, currently there is a tunnel1 sourcing from 163.81.217.122 and the tunnel destination is 163.81.217.138 and this is working ok...

 

Then we need to have a backup from RtrB. When I create a tunnel2 sourcing from 159.42.205.242 and the tunnel destination is the same as tunnel1 which is 163.81.217.138, it's not coming up.

 

Is it possible for this design?

 

RtrB - dual connection to RtrA but RtrA only have 1 connection to RtrB.

 

Thank you

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So from the original question...

 

is it possible to have two gre tunnels using same source but each tunnel has it's own destination??

 

My question is

 

is it possible to have two gre tunnels using different source (RtrB =2xcircuit) but each tunnel has it's the same destination (RtrA = 1xcircuit) ??

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