[Swan] LibreSwan VPN Established | No Data Passing Through

Nick Howitt nick at howitts.co.uk
Fri Nov 18 18:58:00 EET 2022

On 18/11/2022 16:07, Paul Wouters wrote:
> On Fri, 18 Nov 2022, Kumar P S Udai wrote:
>> One is at the HO establishing connection to three other branch 
>> offices, while all three are
>> getting connected, at one branch office the public IP is not 
>> configured on the machine directly,
>> but on an external vendor's router.  Initially I had trouble 
>> establishing connection to this unit,
>> but after a lot of reading and config change, the connection is 
>> getting established now, but I
>> cannot ping or reach each other.  Attaching the config details FYI 
>> please.  Would appreciate any
>> help from the community.
>> 000 #45: "PLSUBNET" esp.716c376b at esp.fdc71b0a at 
>> tun.0 at
>> tun.0 at Traffic: ESPin=1KB ESPout=0B! ESPmax=0B
> Note traffic coming in, but no traffic going out.
>> 000 #6276: "PLUTOSUBNET" esp.fdc71b0a at esp.716c376b at 
>> tun.0 at tun.0 at
>> Traffic: ESPin=0B ESPout=1KB! ESPmax=0B
>> 000
> traffic going out, but no traffic coming in.
> I suspect that on machine PLUTO, there is a NAT rule that ends up NATing
> the traffic before it gets to be IPsec'ed
> On PLUTO try:
> iptables -I FORWARD -t nat -s  -d -j RETURN
Don't you want the POSTROUTING rule from 
https://libreswan.org/wiki/FAQ#NAT_.2B_IPsec_is_not_working? I don't 
believe there is a FORWARD chain in the nat table.

If you want a FORWARD rule as well, you can use the generic:
iptables -I FORWARD -m policy --dir in --pol ipsec -j ACCEPT

Then you don't have to bother about subnets.


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