Using Loopback interfaces for a site-to-site IPSEC VPN

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Using Loopback interfaces for a site-to-site IPSEC VPN

L1 Bithead

Does anybody have experience configuring site-to-site IPSEC VPNs using loopback interfaces instead of phsical ones?  If you are going to respond with a sassy comment (e.g. Why are you doing that?  or That's dumb!) then please don't respond.  I have a specific need.  I have the VPN setup.  I can send traffic to the remote end, but it appears that the firewall drops the returning ESP packets upon return.  I don't see that in the logs, but rather when performing a network capture within the firewall.  The firewall records the returning ESP packets in the receive and drop logs.  I've been busting my head trying to figure this one out along with others in my circle, but we just can seem to crack this baby.


I will be happy to share my config, or perform a web-ex with you  in order to get to the bottom of this.


Your assistance in appreciated...





L4 Transporter



 you need to ensure that your loopback is in same zone than the external interface.


 Anyway, this is not a supported design and I know TAC may refuse to support it. I have seen issues as well.

L5 Sessionator


I don't see why you shouldn't use loopback interface for IPSEC?



Usual when the packets aren't forwarded and there is nothing in logs it's a routing issue. So I'd suggest to check routing. Maybe the rule is written to forward packets to an interface instead of IP address? 

Also if you're behind NAT check if there's a NAT rule for 'any' service as ESP can't be NAT-ed specifically.



@santonic because my experiences over 5 years on the product instructs that there are issues and also because I am 90% sure TAC will say it is not supported as they did for 2 of my customers.

Cyber Elite
Cyber Elite

Hi Merrick


could you provide some more information regarding your config? There are several different ways to configure ipsec on a loopback interface, having some insight into how you set it up may help: is there NAT, which zones are being used, how did you configure the ike gateway objects ...


In general it would be recommended to set the loopback in the external zone and assign it a public IP, this will make for the least complexity as NAT and different zones could require complex policies depending on your overal design plus some options may not be available






Tom Piens
PANgurus - (co)managed services and consultancy
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