Intermittent vpn problems

[robert]

Hi all,

When connecting to a Microsoft VPN server using GRE and pppd,
sometimes I cannot get any responses to these sends:

sent [LCP ConfReq id=0x1 <mru 1000> <asyncmap 0x0> <magic 0x4d35fa6>
<pcomp> <accomp>]

Using nmap to the ip and port works:

/root> nmap -p1723 x.
99.45.107

Starting Nmap 5.00 ( http://nmap.org ) at 2009-12-28 13:01 BRT
Interesting ports on vpn.x.com (x.99.45.107):
PORT STATE SERVICE
1723/tcp open pptp

I have some tcpdump info, but besides telling me that its failing, I
don't see where the problem is. Here's a tcpdump log on a successful
connect:

http://braziloutsource.com/random/my_good.tcpdump.txt

And here's tcpdump log on a failed connect:

http://braziloutsource.com/random/my_bad.tcpdump.txt

I tried hping2 (hping3 gave me a compile error) but it just hangs here
with no progress, I left it running here for over 12 hours:

/root> hping2 -I br0 -0 -H 47 -d 10 --traceroute x.99.45.107
HPING x.99.45.107 (br0 x.99.45.107): raw IP mode set, 20 headers +
10 data bytes
hop=1 TTL 0 during transit from ip=192.168.15.1 name=UNKNOWN

Where my br0 interface is:

/root> ifconfig
br0 Link encap:Ethernet HWaddr 00:19:D1:88:48:57
inet addr:192.168.15.33 Bcast:192.168.15.255 Mask:
255.255.255.0
inet6 addr: fe80::219:d1ff:fe88:4857/64 Scope:Link
UP BROADCAST RUNNING MULTICAST MTU:1500 Metric:1
RX packets:1045242 errors:0 dropped:0 overruns:0 frame:0
TX packets:1039820 errors:0 dropped:0 overruns:0 carrier:0
collisions:0 txqueuelen:0
RX bytes:1038685206 (990.5 Mb) TX bytes:370758098 (353.5
Mb)

As I said, this problem is intermittent. Once I can connect, I usually
can stay connected for days. However, when I can't connect, I often
have to wait several hours and then it just works. Our sys admin guy
says "it works for me using Windows" :-( .

Any ideas?
- R

[Chris Cox]

robert wrote:
...

> As I said, this problem is intermittent. Once I can connect, I usually
> can stay connected for days. However, when I can't connect, I often
> have to wait several hours and then it just works. Our sys admin guy
> says "it works for me using Windows" :-( .

Well... your sys admin is either saying that he's stupid... or that
company policy prohibits the use of Linux. If not the latter, I'd
escalate the issue so that your sys admin starts learning new things.

If lcp stuff is getting in the way, you can try disabling (commenting
out) all the lcp options in your pppd.conf and see if that makes things work
better.