RT-AC86U PPTP VPN User limit?

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8tpercent

New Around Here
Hi,

I've got a new router....RT-AC86U

Currently running stock firmware:

Current Version : 3.0.0.4.384_32799-gfe72567

I've setup 10 pptp usernames.

6 clients can connect at the same time with no issue... however when the 7th one connects they get a port closed error on windows.

Here's the router log when the 7th client connects....

Sep 15 11:41:50 pptp[8183]: pppd 2.4.7 started by admin, uid 0
Sep 15 11:41:50 pptp[8183]: Couldn't allocate PPP unit 10 as it is already in use
Sep 15 11:41:50 pptp[8183]: Couldn't allocate PPP unit 11 as it is already in use
Sep 15 11:41:50 pptp[8183]: Couldn't allocate PPP unit 12 as it is already in use
Sep 15 11:41:50 pptp[8183]: Couldn't allocate PPP unit 13 as it is already in use
Sep 15 11:41:50 pptp[8183]: Couldn't allocate PPP unit 14 as it is already in use
Sep 15 11:41:50 pptp[8183]: Couldn't allocate PPP unit 15 as it is already in use
Sep 15 11:41:50 pptp[8183]: ioctl (SIOCGIFINDEX): No such device (line 2286)
Sep 15 11:41:50 pptp[8183]: Connect: ppp16 <--> pptp (x.x.x.x)
Sep 15 11:41:50 pptp[8183]: ioctl(SIOCSIFMTU): No such device (line 1207)
Sep 15 11:41:50 pptp[8183]: Couldn't get PPP statistics: No such device
Sep 15 11:41:50 pptpd[8182]: CTRL: Ignored a SET LINK INFO packet with real ACCMs!
Sep 15 11:41:50 pptp[8183]: ioctl(SIOCSIFADDR): No such device (line 2433)
Sep 15 11:41:50 pptp[8183]: Couldn't get PPP statistics: No such device
Sep 15 11:41:50 pptp[8183]: ioctl (SIOCGIFFLAGS): No such device (line 2390)
Sep 15 11:41:50 pptp[8183]: ioctl(SIOCSIFADDR): No such device (line 2553)
Sep 15 11:41:50 pptp[8183]: MPPE 128-bit stateless compression enabled
Sep 15 11:41:50 pptp[8183]: Couldn't get PPP statistics: No such device
Sep 15 11:41:50 pptp[8183]: MPPE disabled
Sep 15 11:41:53 pptp[8183]: Connection terminated.
Sep 15 11:41:53 pptp[8183]: Modem hangup

Is there a limit on connections for PPTP ? Is this fixed in an updated firmware or even Merlin firmware?

If one of the 6 vpn users disconnects.... the 7th user can connect.... but if the 6th vpn user tries to reconnect... they can't.

Any help would be great an trouble shooting.

Thank You.
 

eibgrad

Very Senior Member
JMTC

I haven't used PPTP server (or client) since probably 2014, due to well-known and unresolvable security concerns w/ the protocol. So even though I use Merlin (and presumably the OEM/stock firmware is quite similar, perhaps identical), I have no way of knowing if indeed the PPTP server is limited to 6 concurrent users. On the face of it, the Advanced Settings option on the PPTP server configuration page would at least suggest the limit was 10 based on Client IP address (for Merlin it reports a max of 30 for my RT-AC68U).


Even if this was a bug, there's virtually no chance it could/would be corrected given you're using OEM/stock firmware (Merlin at least provides some hope, but even then …), and given PPTP is considered effectively deprecated by the community. Even many mobile devices have already eliminated PPTP as a client (e.g., iOS). In short, everything is working against you should you decide to stick w/ PPTP. You'd have to hope there's some miracle, magical fix that I'm unaware of.

OTOH, using OpenVPN server, something similar is NOT possible, since unlike PPTP where every client gets allocated and assigned its own PPP network interface (ppp0, ppp1, ppp2, etc.), every OpenVPN client shares the only and only network interface (e.g., tun21).

I know that's what longtime PPTP users don't want to hear. But as soon as you run into problems, and unless you just get lucky and run into something known to be easily fixable, you're in trouble, because the rest of the VPN world has long since moved to OpenVPN, WireGuard, etc. No one is going to waste their time debugging deprecated technology. In fact, I wouldn't be surprised if you reported it to ASUS that they told you to use OpenVPN!

I know that seems kind of harsh. But I purposely held back in the hopes someone might have seen this specific problem before and have a quick and easy answer. Since that hasn't happened so far, I decided to throw in my two cents, FWIW.
 

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