Hi All, I have purchased a Synology disk station DS411j and I have set up a PPTPD server onto it.
I am connecting with a Win7 PPTP client successfully onto the PPTPD server, once authenticated and connected, I can ping from the Win7 to the ppp0 interface inside the tunnel, but only for a brief while. After waiting for 20 seconds or so I would retry the ping and can't ping the ppp0 interface anymore.

My Synology disk station has 1 ethernet interface eth0 with ip address 192.168.1.253/24 gw 192.168.1.254 (belkin router) which is providing the internet for the synology box.

Client connection was over the internet to the synology box, port 1723 and GRE passthrough are apparently working since I can connect and login to the PPTPD server.

CLIENT WIN7 PPTP IF PTP ppp0 (syno box)eth0
192.168.1.51 <--------------> 192.168.1.50 192.168.1.253/24, gw 192.168.1.254

I got proxy arp set up in my pptpd config file

uname -a gives me the following information:
Linux DiskStation 2.6.32.12 #2228 Thu May 10 02:19:28 CST 2012 armv5tel GNU/Linux synology_88f6281_411j

these is my pptpd.conf:
-----------------------
ppp /usr/sbin/pppd
option options.pptpd
#logwtmp
localip 192.168.1.50
remoteip 192.168.1.51-60


this is my options.pptpd:
-------------------------
require-mppe
require-mschap-v2
refuse-mschap
refuse-chap
refuse-pap
name pptpd
ms-dns 192.168.1.254
ms-wins 192.168.1.253
mtu 1300
mru 1300
nomppe-lower-mtu
proxyarp
#debug
lock
nopcomp
noaccomp
nobsdcomp
novj
novjccomp
nologfd
plugin /var/packages/VPNCenter/target/lib/pppd/2.4.5/radius.so
plugin /var/packages/VPNCenter/target/lib/pppd/2.4.5/radattr.so

Can anybody please help me with this issue? I have been pulling my hair out on this one for several days now, and can't seem to find any solution ...