Re: MTU size

Thanks James,


On Thu, Nov 21, 2013 at 9:02 PM, James Cameron <[email protected]> wrote:

> On Thu, Nov 21, 2013 at 01:19:54PM +0000, Khapare Joshi wrote:
> > ppp: compressor dropped pkt
> > mppe_compress[31]: osize too small! (have: 1404 need: 1408)
>
> These two messages are from kernel level ppp driver, not pptpd, so I
> have not kept necessary knowledge.  I suggest you look for a kernel
> upgrade from your Linux distribution, try the latest stable Linux
> kernel (3.12), or check bug trackers for the kernel.
>

I updated the kernel :
kernel-2.6.32-358.2.1.el6.x86_64 to kernel-2.6.32-358.23.2.el6.x86_64


>
> On the face of the meaning of the two messages, during encryption or
> compression, the packet grew and would not fit, and was discarded.
> This may cause hangs of HTTP get.
>
I am guessing this is the issue, so upgrading the above kernel did not
help. but yes maybe 3.12 (when this comes in centos repo )

>
> > these is only few users who are having issue, I will monitor their
> > vpn connection and change the MTU size if needed. But where can I
> > make change the MTU in VPN server ? is it in /etc/ppp/ip-up file ?
>
> Yes.
>
> ifconfig ${1} mtu 1200
>

this is my ip-up contents

 !/bin/bash
# This file should not be modified -- make local changes to
# /etc/ppp/ip-up.local instead

PATH=/sbin:/usr/sbin:/bin:/usr/bin
export PATH

LOGDEVICE=$6
REALDEVICE=$1

[ -f /etc/sysconfig/network-scripts/ifcfg-${LOGDEVICE} ] &&
/etc/sysconfig/network-scripts/ifup-post --realdevice ${REALDEVICE}
ifcfg-${LOGDEVICE}

#/etc/ppp/ip-up.ipv6to4 ${LOGDEVICE}

#[ -x /etc/ppp/ip-up.local ] && /etc/ppp/ip-up.local "$@"

/sbin/ifconfig $1 mtu 1400
exit 0

PS: mtu 1400 ( i am testing )

>
> (you may need to use a different variable name, do some research into
> existing scripts)
>
> > And, I see constantly following in the ppp.log files, could you
> > please give me some hint or direction on resolving these issue ?
> >
> > Nov 17 15:59:58 myvpn pptpd[32735]: MGR: dropped small initial connection
> > Nov 19 17:58:50 myvpn pptpd[32735]: MGR: dropped slow initial connection
> > Nov 19 19:35:16 myvpn pptpd[32735]: MGR: dropped slow initial connection
> > Nov 20 10:57:20 myvpn pptpd[32735]: MGR: dropped small initial connection
> > Nov 20 20:45:19 myvpn pptpd[32735]: MGR: dropped small initial connection
>
> These are not an error, and will occur during either:
>
> 0.  port probing,
>
> 1.  automated robotic attacks on pptpd servers from the internet,
>
> 2.  users trying to start tunnel when their network link is saturated, or;
>
> 3.  saturation of the server's network link.
>
> > Nov 17 08:32:17 myvpn pppd[27865]: Protocol-Reject for unsupported
> protocol 0xb5
> > Nov 17 08:32:17 myvpn pppd[27865]: rcvd [LCP ProtRej id=0x73 d2 f5 79 0b
> 84 9c a4 ed 92 9c eb 76 88 e1 ce 0c 93 22 aa d3 03 ec 86 d0 91 3c d2 36 73
> ea 37 7b ...]
> > Nov 17 08:32:17 myvpn pppd[27865]: Protocol-Reject for unsupported
> protocol 0xd2f5
>
> Incompatibility in software versions, refusal of the peer to follow
> options negotiated, router firmware flaws, or corruption of packets.
>
> > Nov 21 11:05:37 myvpn pppd[15722]: Refusing MPPE stateful mode offered
> by peer
> > Nov 21 11:05:37 myvpn pppd[15722]: MPPE required but peer negotiation
> failed
>
> Misconfiguration of peer.
>
> These are symptoms, not problems.  I cannot tell if these symptoms
> relate to any problem.
>
> --
> James Cameron
> http://quozl.linux.org.au/
>

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