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Connecting to a Ubiquiti Unifi VPN with a Linux machine
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| This guide assumes that you have already set up a Ubiquiti Unifi VPN following the guide: | |
| https://help.ubnt.com/hc/en-us/articles/115005445768-UniFi-L2TP-Remote-Access-VPN-with-USG-as-RADIUS-Server | |
| To configure a Linux machine to be able to connect remotely I followed these steps. This guide was written for Debian 8. | |
| - In Debian install the "xl2tpd" and "strongswan" packages. | |
| - Edit /etc/ipsec.conf to add the connection: | |
| conn YOURVPNCONNECTIONNAME | |
| authby=secret | |
| pfs=no | |
| auto=start | |
| keyexchange=ikev1 | |
| keyingtries=3 | |
| dpddelay=15 | |
| dpdtimeout=45 | |
| dpdaction=clear | |
| rekey=no | |
| ikelifetime=3600 | |
| keylife=3600 | |
| type=transport | |
| left=%defaultroute | |
| leftprotoport=17/1701 | |
| # Replace IP address with your VPN server's IP | |
| right=IPADDRESSOFVPNSERVER | |
| rightprotoport=17/%any | |
| ike=aes128-sha1-modp2048,aes256-sha1-modp4096,aes128-sha1-modp1536,aes256-sha1-modp2048,aes128-sha1-modp1024,aes256-sha1-modp1536,aes256-sha1-modp1024,3des-sha1-modp1024! | |
| esp=aes128-sha1-modp2048,aes256-sha1-modp4096,aes128-sha1-modp1536,aes256-sha1-modp2048,aes128-sha1-modp1024,aes256-sha1-modp1536,aes256-sha1-modp1024! | |
| - Edit /etc/ipsec.secrets to add the secret key for this connection: | |
| IPADDRESSOFVPNSERVER : PSK "SECRETPRESHAREDKEY" | |
| - Edit /etc/xl2tpd/xl2tpd.conf to add this connection: | |
| [lac YOURVPNCONNECTIONNAME] | |
| lns = IPADDRESSOFVPNSERVER | |
| ppp debug = yes | |
| pppoptfile = /etc/ppp/options.l2tpd.client-YOURVPNCONNECTIONNAME | |
| length bit = yes | |
| - Create the file /etc/ppp/options.l2tpd.client-YOURVPNCONNECTIONNAME: | |
| ipcp-accept-local | |
| ipcp-accept-remote | |
| noccp | |
| refuse-eap | |
| refuse-chap | |
| noauth | |
| idle 1800 | |
| mtu 1410 | |
| mru 1410 | |
| defaultroute | |
| # Uncomment if you want to use the DNS servers of the VPN host: | |
| #usepeerdns | |
| debug | |
| logfile /var/log/xl2tpd.log | |
| connect-delay 5000 | |
| proxyarp | |
| name VPNUSERNAME | |
| password "VPNPASSWORD" | |
| - Now to connect to the VPN create a script: | |
| #!/bin/bash | |
| echo "Connecting to VPN..." | |
| echo "c YOURVPNCONNECTIONNAME" > /var/run/xl2tpd/l2tp-control | |
| sleep 10 | |
| # To have all internet traffic routed through the VPN uncomment: | |
| #ip route add default dev ppp0 | |
| # To only have a remote subnet routed through the VPN uncomment | |
| # (this line assumes the remote subnet you want routed is 192.168.0.0/24 and the remote VPN end is 10.11.0.1: | |
| ip route add 192.168.0.0/24 via 10.11.0.1 dev ppp0 | |
| - And to disconnect to the VPN create a script: | |
| #!/bin/bash | |
| ip route del default dev ppp0 | |
| ip route del 192.168.0.0/24 dev ppp0 | |
| echo "d YOURVPNCONNECTIONNAME" > /var/run/xl2tpd/l2tp-control | |
| service xl2tpd restart | |
| - Note that for these scripts I am assuming that the remote subnet we are interested in is 192.168.0.0/24 | |
| and the remote VPN gateway address is 10.11.0.1. | |
| - You can also decide which line to uncomment based on if you want all traffic to be routed through the VPN | |
| or to just route connections to the 192.168.0.0/24 subnet. | |
| - If you want all traffic routed through the VPN you may want to uncomment the "usepeerdns" line in | |
| /etc/ppp/options.l2tpd.client-YOURVPNCONNECTIONNAME so that DNS traffic flows through the VPN rather | |
| than going to the local DNS server. |
I think I won't be able to go higher than this since 3600s is also what's configured on UDM side ( in /run/strongswan/ipsec.d/tunnels/lns-l2tp-server.ipsec.l2tp.config) but I can try :)
This is the sequence of events I see in my logs if that helps :
Oct 26 12:33:02 servername pppd[312446]: sent [LCP EchoReq id=0x78 magic=0xf47f4c94]
Oct 26 12:33:02 servername charon: 16[IKE] sending DPD request
Oct 26 12:33:02 servername charon: 16[ENC] generating INFORMATIONAL_V1 request 3876004764 [ HASH N(DPD) ]
Oct 26 12:33:02 servername charon: 16[NET] sending packet: from {serverIP}[500] to {udmIP}[500] (92 bytes)
Oct 26 12:33:10 servername charon: 05[NET] received packet: from {udmIP}[500] to {serverIP}[500] (540 bytes)
Oct 26 12:33:10 servername charon: 05[ENC] parsed ID_PROT request 0 [ SA V V V V V ]
Oct 26 12:33:10 servername charon: 05[IKE] received XAuth vendor ID
Oct 26 12:33:10 servername charon: 05[IKE] received DPD vendor ID
Oct 26 12:33:10 servername charon: 05[IKE] received FRAGMENTATION vendor ID
Oct 26 12:33:10 servername charon: 05[IKE] received NAT-T (RFC 3947) vendor ID
Oct 26 12:33:10 servername charon: 05[IKE] received draft-ietf-ipsec-nat-t-ike-02\n vendor ID
Oct 26 12:33:10 servername charon: 05[IKE] {udmIP} is initiating a Main Mode IKE_SA
Oct 26 12:33:10 servername charon: 05[CFG] selected proposal: IKE:AES_CBC_128/HMAC_SHA1_96/PRF_HMAC_SHA1/MODP_2048
Oct 26 12:33:10 servername charon: 05[ENC] generating ID_PROT response 0 [ SA V V V V ]
Oct 26 12:33:10 servername charon: 05[NET] sending packet: from {serverIP}[500] to {udmIP}[500] (160 bytes)
Oct 26 12:33:10 servername charon: 12[NET] received packet: from {udmIP}[500] to {serverIP}[500] (372 bytes)
Oct 26 12:33:10 servername charon: 12[ENC] parsed ID_PROT request 0 [ KE No NAT-D NAT-D ]
Oct 26 12:33:10 servername charon: 12[ENC] generating ID_PROT response 0 [ KE No NAT-D NAT-D ]
Oct 26 12:33:10 servername charon: 12[NET] sending packet: from {serverIP}[500] to {udmIP}[500] (372 bytes)
Oct 26 12:33:10 servername charon: 09[NET] received packet: from {udmIP}[500] to {serverIP}[500] (76 bytes)
Oct 26 12:33:10 servername charon: 09[ENC] parsed ID_PROT request 0 [ ID HASH ]
Oct 26 12:33:10 servername charon: 09[CFG] looking for pre-shared key peer configs matching {serverIP}...{udmIP}[{udmIP}]
Oct 26 12:33:10 servername charon: 09[CFG] selected peer config "UDM"
Oct 26 12:33:10 servername charon: 09[IKE] detected reauth of existing IKE_SA, adopting 1 children and 0 virtual IPs
Oct 26 12:33:10 servername charon: 09[IKE] schedule delete of duplicate IKE_SA for peer '{udmIP}' due to uniqueness policy and suspected reauthentication
Oct 26 12:33:10 servername charon: 09[IKE] IKE_SA UDM[24] established between {serverIP}[{serverIP}]...{udmIP}[{udmIP}]
Oct 26 12:33:10 servername charon: 09[ENC] generating ID_PROT response 0 [ ID HASH ]
Oct 26 12:33:10 servername charon: 09[NET] sending packet: from {serverIP}[500] to {udmIP}[500] (76 bytes)
Oct 26 12:33:10 servername charon: 11[NET] received packet: from {udmIP}[500] to {serverIP}[500] (572 bytes)
Oct 26 12:33:10 servername charon: 11[ENC] parsed QUICK_MODE request 3923868918 [ HASH SA No KE ID ID ]
Oct 26 12:33:10 servername charon: 11[CFG] selected proposal: ESP:AES_CBC_128/HMAC_SHA1_96/MODP_2048/NO_EXT_SEQ
Oct 26 12:33:10 servername charon: 11[IKE] received 3600s lifetime, configured 0s
Oct 26 12:33:10 servername charon: 11[ENC] generating QUICK_MODE response 3923868918 [ HASH SA No KE ID ID ]
Oct 26 12:33:10 servername charon: 11[NET] sending packet: from {serverIP}[500] to {udmIP}[500] (444 bytes)
Oct 26 12:33:10 servername charon: 08[NET] received packet: from {udmIP}[500] to {serverIP}[500] (60 bytes)
Oct 26 12:33:10 servername charon: 08[ENC] parsed QUICK_MODE request 3923868918 [ HASH ]
Oct 26 12:33:10 servername charon: 08[IKE] CHILD_SA UDM{3} established with SPIs c0c1d95b_i cf703f9a_o and TS {serverIP}/32[udp/l2f] === {udmIP}/32[udp]
Oct 26 12:33:11 servername xl2tpd[845]: check_control: Received out of order control packet on tunnel 41163 (got 62, expected 61)
Oct 26 12:33:11 servername xl2tpd[845]: handle_packet: bad control packet!
Oct 26 12:33:17 servername charon: 13[IKE] sending DPD request
Oct 26 12:33:17 servername charon: 13[ENC] generating INFORMATIONAL_V1 request 1354316911 [ HASH N(DPD) ]
Oct 26 12:33:17 servername charon: 13[NET] sending packet: from {serverIP}[500] to {udmIP}[500] (92 bytes)
Oct 26 12:33:20 servername charon: 10[IKE] deleting IKE_SA UDM[23] between {serverIP}[{serverIP}]...{udmIP}[{udmIP}]
Oct 26 12:33:20 servername charon: 10[IKE] sending DELETE for IKE_SA UDM[23]
Oct 26 12:33:20 servername charon: 10[ENC] generating INFORMATIONAL_V1 request 705273687 [ HASH D ]
Oct 26 12:33:20 servername charon: 10[NET] sending packet: from {serverIP}[500] to {udmIP}[500] (92 bytes)
Oct 26 12:33:26 servername charon: 16[NET] received packet: from {udmIP}[500] to {serverIP}[500] (92 bytes)
Oct 26 12:33:26 servername charon: 16[ENC] parsed INFORMATIONAL_V1 request 3966655131 [ HASH N(DPD) ]
Oct 26 12:33:26 servername charon: 16[ENC] generating INFORMATIONAL_V1 request 2641383276 [ HASH N(DPD_ACK) ]
Oct 26 12:33:26 servername charon: 16[NET] sending packet: from {serverIP}[500] to {udmIP}[500] (92 bytes)
Oct 26 12:33:27 servername xl2tpd[845]: Maximum retries exceeded for tunnel 62873. Closing.
Oct 26 12:33:27 servername xl2tpd[845]: Terminating pppd: sending TERM signal to pid 312446
Sorry, I don't really know what's going on. I haven't tried doing this kind of VPN in a few months so I'm not sure if Ubiquiti has changed something or not. Is there anyone else following this gist who has seen this, or has a VPN that continues to work fine for more than 1 hour?
I have had a working system for a little while now. I am running Mint 20
Ulyana - I upgraded from v18 a while back because I struggled to get the
VPN working even though I was trying things people said worked, such as
using different network management packages and fiddling with ipsec.conf.
The good thing is even when Microsoft releases updates that break it on
Windows clients (I think that was early this year), I was unaffected.
After the upgrade I have not had to do anything - just create the
connection via the GUI and it works perfectly. Have left it on for a whole
day when I forgot to disconnect before going to work - come home and still
connected.
Not really helpful, since it is the standard unhelpful answer - upgrade:-)
Peter Bisset
…On Thu, 27 Oct 2022 at 01:45, Nick Hall ***@***.***> wrote:
***@***.**** commented on this gist.
------------------------------
Sorry, I don't really know what's going on. I haven't tried doing this
kind of VPN in a few months so I'm not sure if Ubiquiti has changed
something or not. Is there anyone else following this gist who has seen
this, or has a VPN that continues to work fine for more than 1 hour?
—
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will this work on the Unifi UDM as well?
will this work on the Unifi UDM as well?
I would think so but I haven't tried that.
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Hmm, that's strange, I haven't seen that. Have you tried increasing ikelifetime and keylife in /etc/ipsec.conf to see if that stops the drop? In my example they are set to 3600 seconds which corresponds to 1 hour so you could increase them and see if it goes longer without dropping. But it's not actually supposed to drop when that lifetime expires.