Security Basics mailing list archives
RE: Linux PPTP VPN server - can't map Windows shares/printers
From: Peter Mueller <pmueller () sidestep com>
Date: Mon, 24 Nov 2003 12:46:19 -0800
Hello,
My MTU setting in /etc/ppp/options.pptpd is currently set to 1450. I wouldn't imagine that this is too low, but as this is my first VPN server, I'm open to suggestions. However, I believe this to be a problem with routing the appropriate data through the server.
Theoretically MTU is supposed to resize automagically through the use of certain ICMP packets. I found this didn't occur for me with the latest poptop-CVS, so.. <snip /etc/ppp/options.pptpd> # MTU/MRU setting: # TCP header = 20 byte # IP header = 20 byte # GRE header = 24 byte # PPP header = 8 byte # MPPE header = 2 byte # GRE over Eth: 1500 - 24 = 1476 MTU (-20 -20 = 1436 MSS) # GRE over PPP over Eth: 1500 - 8 - 24 = 1468 MTU (-20 -20 = 1428 MSS) -> used with PPPoE adsl # GRE over PPP over Eth with MPPE: 1500 - 8 - 24 - 2 = 1466 MTU (-20 -20 = 1426 MSS) -> used with PPPoE adsl </snip> I found it was necessary to change the MTU in /etc/ppp/ip-up in my particular setup. This was because I was trying to connect to an IPSec-connected remoted network. Note that this doesn't change the MRU, but I found that it wasn't necessary in my setup. <snip /etc/ppp/ip-up> #!/bin/bash # This file should not be modified -- make local changes to # /etc/ppp/ip-up.local instead LOGDEVICE=$6 REALDEVICE=$1 export PATH=/sbin:/usr/sbin:/bin:/usr/bin [ -x /etc/ppp/ip-up.local ] && /etc/ppp/ip-up.local $* # Used for clustering heartbeat monitoring stuff. [ -x /etc/ppp/ip-up.heart ] && /etc/ppp/ip-up.heart $* /etc/sysconfig/network-scripts/ifup-post ifcfg-${LOGDEVICE} /sbin/ifconfig $1 mtu 1442 # <-- add this line exit 0 </snip> Hope it helps. Peter M. --------------------------------------------------------------------------- ----------------------------------------------------------------------------
Current thread:
- Linux PPTP VPN server - can't map Windows shares/printers NetNITCO Systems Administration (Nov 21)
- Re: Linux PPTP VPN server - can't map Windows shares/printers Kevin Saenz (Nov 23)
- Re: Linux PPTP VPN server - can't map Windows shares/printers NetNITCO Systems Administration (Nov 24)
- <Possible follow-ups>
- Re: Linux PPTP VPN server - can't map Windows shares/printers Mitchell Rowton (Nov 21)
- Re: Linux PPTP VPN server - can't map Windows shares/printers NetNITCO Systems Administration (Nov 24)
- RE: Linux PPTP VPN server - can't map Windows shares/printers Peter Mueller (Nov 25)
- Re: Linux PPTP VPN server - can't map Windows shares/printers Kevin Saenz (Nov 23)