[Firewall] Using IPSec (w/o Racoon)
jeff.welling at gmail.com
Wed Jul 16 12:56:06 MDT 2008
I had trouble getting IPSec to work through NATs, I kept getting an
error along the lines of 'packet too small, retramsitting'. When there
was no NAT involved it worked like a charm though. I was not able to
pin down the cause of that error message.
Philip Prindeville wrote:
> I'm hoping to get automagic creation of IPSec tunnels into the next
> release of Astlinux, but this is a showstopper on that capability.
> Let me know if you have some time to stare at this issue some. I can
> run tests.
> Arno van Amersfoort wrote:
>> What kind of IPsec implementation are you using? Freeswan, Racoon or
>> something else. The FAQ is a little outdated, and this explanation only
>> works with Freeswan (which is obsolete AFAIK).
>> Philip Prindeville wrote:
>>> I read the FAQ. Saw:
>>> *Q:* Does your firewall work with IPSEC (Freeswan)?
>>> *A:* YES! :-) Here's how you should do it, it's actually quite easy with
>>> my script.
>>> You need to configure the following variables:
>>> - OPEN_IP="50 51" # 50 = ESP protocol, 51 = AH protocol
>>> - OPEN_UDP="500 4500" # 500 = IKE port. 4500 (=optional) = NAT traversal
>>> - TRUSTED_IF="ipsec+" # This allows the actual freeswan traffic to your
>>> gateway/network. You should probably also add "ppp+" but note that this
>>> only works if you don"t use ppp+ for your external interface (EXT_IF)!
>>> - RP_FILTER=0 # If we don't do this the private external addresses won't
>>> be routed into our net
>>> I'm trying to get a statically configured tunnel using setkey (hence not
>>> using Racoon for dynamic key exchange via DH).
>>> I don't have any interfaces called "ipsec*", and in one case I'm doing
>>> Metropolitan ethernet (or PONS, so no PPPoE) and in the other case, my
>>> ppp0 is my EXT_IF.
>>> So, what to do?
>>> How do I get things working in this corner case?
>>> I ran:
>>> tcpdump -s 1500 -n -l -i ppp0 \( udp port 500 or udp port 4500 or esp or
>>> ah \)
>>> but didn't see squat... neither inbound nor outbound.
>>> Has anyone had success with IPSec that could share some pointers?
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