[strongSwan] Running on AWS behind Elastic IP

Bruce Ferrell bferrell at baywinds.org
Wed Nov 16 06:34:22 CET 2016

Try setting it up as if the AWS instance is a netting host

On 11/15/2016 09:27 PM, Mathew Marulla wrote:
> First some background…
> Our current installation is using ipsec-tools/racoon running on a CentOS server at Rackspace to establish two VPN tunnels to hardware routers at remote installations.  146.x.x.x
> is a Cisco 2500 and 2.x.x.x is a Comtrend VG-8050.  Both remote locations have several servers in subnets that talk over the VPN (10.2.2.x in one location and 10.2.3.x in the
> other), but they only need to talk to the local server that is running the VPN, so no local subnet, just one server (184.x.x.x).  We’ve been running this successfully for several
> years.
> We are now moving the local installation to AWS and updating lots of infrastructure.  The local server is now running Ubunutu 14.04 and StrongSwan 5.5.1.  It is behind an elastic
> IP (52.x.x.x).  The remote installations and hardware have not changed, other than adding the new VPNs to the 52.x.x.x server.  We still don’t need to have a local subnet, but
> you will see one in the config below - i’ve tried almost everything.
> Although I have read just about every tutorial and similar posting I can find about running StrongSwan on an EC2 instance, I still can not seem to get it to work.
> Here’s the config files (private info and public IPs edited out):
> strongswan.conf
>> charon {
>> load_modular = yes
>> plugins {
>> include strongswan.d/charon/*.conf
>> }
>> }
>> include strongswan.d/*.conf
> ipsec.conf
>> config setup
>>   strictcrlpolicy=no
>>   charondebug=all
>> conn %default
>>   ikelifetime=1h
>>   lifetime=1h
>>   authby=psk
>>   auto=start
>> conn xxxxx
>>   left=
>>   leftid=52.x.x.x
>>   leftsubnet=
>>   leftauth=psk
>>   right=2.x.x.x
>>   rightsubnet=
>>   rightauth=psk
>>   ike=aes128-sha1-modp1024!
>>   esp=aes128-sha1-modp1024!
>>   aggressive=no
> When I try to run ipsec, I get this:
>> Starting strongSwan 5.5.1 IPsec [starter]...
>> 00[DMN] Starting IKE charon daemon (strongSwan 5.5.1, Linux 3.13.0-74-generic, x86_64)
>> 00[CFG] loading ca certificates from '/etc/ipsec.d/cacerts'
>> 00[CFG] loading aa certificates from '/etc/ipsec.d/aacerts'
>> 00[CFG] loading ocsp signer certificates from '/etc/ipsec.d/ocspcerts'
>> 00[CFG] loading attribute certificates from '/etc/ipsec.d/acerts'
>> 00[CFG] loading crls from '/etc/ipsec.d/crls'
>> 00[CFG] loading secrets from '/etc/ipsec.secrets'
>> 00[CFG]   loaded IKE secret for 2.x.x.x
>> 00[LIB] loaded plugins: charon aes des rc2 sha2 sha1 md5 random nonce x509 revocation constraints pubkey pkcs1 pkcs7 pkcs8 pkcs12 pgp dnskey sshkey pem fips-prf gmp xcbc cmac
>> hmac attr kernel-netlink resolve socket-default stroke vici updown xauth-generic
>> 00[JOB] spawning 16 worker threads
>> charon (4321) started after 20 ms
>> 08[CFG] received stroke: add connection ‘xxxxx’
>> 08[CFG] added configuration ‘xxxxx’
>> 11[CFG] received stroke: initiate ‘xxxxx’
>> 11[IKE] initiating IKE_SA xxxxx[1] to 2.x.x.x
>> 11[ENC] generating IKE_SA_INIT request 0 [ SA KE No N(NATD_S_IP) N(NATD_D_IP) N(FRAG_SUP) N(HASH_ALG) N(REDIR_SUP) ]
>> 11[NET] sending packet: from[500] to 2.x.x.x[500] (336 bytes)
>> 15[IKE] retransmit 1 of request with message ID 0
>> 15[NET] sending packet: from[500] to 2.x.x.x[500] (336 bytes)
>> 15[IKE] retransmit 2 of request with message ID 0
>> etc…
> I believe it is not connecting because the remote router is seeing a non-routable IP, that is, the private IP of the local server (  I was under the impression that
> the lefdid parameter would be sent so the remote router would see the elastic IP.  That does not seem to be happening.
> Of course, if I put the elastic IP in the left parameter, I get nothing but socket errors since the EC2 instance doesn’t know about it.  I even put the elastic IP in at localhost
> in it’s /etc/hosts file, but no difference.
> Other info:
> Ports 500 and 4500 are open to the remote routers in the EC2 security group.
> net.ipv4.ip_forward is set on.
> IPTables is not running.
> Source/Dest check for this instance is set off in AWS.
> Any ideas? ‘Cause I’m almost out!
> - Matt
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