Dlink-DIR890L VPN Passthrough issue

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DD-WRT Novice

Joined: 24 Jun 2012
Posts: 10

PostPosted: Tue Feb 13, 2018 22:44    Post subject: Dlink-DIR890L VPN Passthrough issue Reply with quote

I noticed that the VPN Passthrough does not work on any of my wirelessly/wire connected devices(Windows PC, MBP laptop, iPhone and iPad), unless i press on any button that say's "Apply Setting", where ever it's located on the router's advanced web based setting page. Once i press on that button, no matter which of the router's setting page i'm on and without changing any of the settings, the VPN passthrough works flawlessly until the router is rebooted and the whole pressing on "Apply Settings" button is followed.

Not sure what is not brought up during the router's startup and only the "Apply Setting" procedure brings it up.

Would be grateful towards any technical support to resolve this issue, that i believe not only me, but many other users will be suffering from.

Thank you in advance.

Joined: 18 Sep 2010
Posts: 6991

PostPosted: Wed Feb 14, 2018 3:37    Post subject: Reply with quote
I don't know what the problem is, but here's an idea.


IOW, try to see what changes once you hit Apply Settings by capturing the state of nvram before and after that event, and comparing the differences. It might provide a clue.
DD-WRT Novice

Joined: 24 Jun 2012
Posts: 10

PostPosted: Wed Feb 14, 2018 20:32    Post subject: Diff between nvram Before and after Reply with quote
Hi Eibgrad,

Thank you for your feedback and your great support. I followed the steps you referred me to and found the only changes was to line number 446 .

Which reads BEFORE as follows :


and AFTER as follows :


Your comments will be highly appreciated.
Thank you once again for your great help.
DD-WRT Novice

Joined: 24 Jun 2012
Posts: 10

PostPosted: Thu Feb 15, 2018 8:03    Post subject: Even more Before and After nvram differences Reply with quote

"line 601" filter_p2p_grp1=0
"line 614" filter_rule1=$STAT:0$NAME:$DENY:0$$
"line 626" filter_tod1=0:0 23:59 0-6
"line 636" filter_tod_buf1=7
"line 677" forward_cur=255

"line 601" "Deleted"
"line 614" filter_rule1=
"line 626" filter_tod1=
"line 636" filter_tod_buf1=
"line 677" forward_cur=253

Joined: 18 Sep 2010
Posts: 6991

PostPosted: Thu Feb 15, 2018 16:16    Post subject: Reply with quote
Can't honestly say the results in this case are useful. And it's not always easy to tell what any given variable is used for. It appears the majority of those are related to AR (Access Restrictions). Perhaps that's the specific button you Applied Settings to?

FWIW, I've been having a similar problem when configuring the OpenVPN client. Darn thing will not start, even though enabled, on boot up unless I hit Apply Settings. Then it works perfectly. But unlike you, it has to be that specific button.

If I had more time to investigate it, I would. But I'm up against a Friday deadline on a project, and so for now I'm just putting up w/ it. But perhaps the bigger takeaway is that I have seen this behavior, and can't always explain it.

Let's step back a second, because it's a little unusual for someone to have a problem and specifically blame VPN passthrough. Esp. when the only observation they've made/reported is based on Apply Settings, and not even necessarily on the PPTP passthrough page.

The only things I know for sure are a) your PPTP client doesn't work, and b) Apply Settings used anywhere fixes it. But it's only an assumption (unless you've investigated this more deeply and made a positive determination) it's specifically PPTP passthrough to blame. Maybe, maybe not.

How specifically are you using PPTP relative to the router? Are you using the PPTP client on the router itself, or have PPTP configured on a client behind the router? And btw, PPTP passthrough is only relevant to the PPTP client, not a PPTP server.

Assuming it is PPTP passthrough, you could try dumping the firewall, before and after Apply Settings. Perhaps the GRE (47) protocol (which is what the PPTP passthrough option directly affects) is missing on reboot, but then gets added once you hit Apply Settings because that's resetting the firewall. Or perhaps it's always there, but gets repositioned from a non-working location to a working location.

iptables -vnL

But if it's always there, and more importantly, always being triggered (pkts or bytes column > 0), that would seem to indicate it is NOT a PPTP passthrough problem.

Lastly, like always w/ these things, it might be worth doing a factory reset. Sometimes that will just clear things up. These routers can get into a bad state more easily than other devices. Esp. when you make major configuration changes w/o first resetting (e.g., standard router to client bridge). Or it could just be a bad build. Been seeing a lot more of these lately than usual.
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