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After update to Fedora 25 one of my PPTP connections strangely works. Remote net is not available.

It is connected, successfully get remote net IP address. While connected nothing is available in remote net, but internet works fine. After a few minutes connection breaks by itself.

I've noticed strange thing, while pptp connection is on there are too much TX packets transferred:

ppp0: flags=4305<UP,POINTOPOINT,RUNNING,NOARP,MULTICAST>  mtu 1400
        inet 192.168.1.96  netmask 255.255.255.255  destination ___.__.___.___
        ppp  txqueuelen 3  (Point-to-Point Protocol)
        RX packets 10  bytes 172 (172.0 B)
        RX errors 0  dropped 0  overruns 0  frame 0
        TX packets 9864041  bytes 5842982146 (5.4 GiB)
        TX errors 0  dropped 0 overruns 0  carrier 0  collisions 0

In a 10-15 seconds it shows up to 5.4 GiB of packets. It grows very fast.

The same if firewalld is disabled.

I'm using Network-Manager to connect to pptp.

[root@c0rp ~]# lsb_release -a
LSB Version:    :core-4.1-amd64:core-4.1-noarch:cxx-4.1-amd64:cxx-4.1-noarch:desktop-4.1-amd64:desktop-4.1-noarch:languages-4.1-amd64:languages-4.1-noarch:printing-4.1-amd64:printing-4.1-noarch
Distributor ID: Fedora
Description:    Fedora release 25 (Twenty Five)
Release:    25
Codename:   TwentyFive
[root@c0rp ~]# uname -a
Linux c0rp 4.10.8-200.fc25.x86_64 #1 SMP Fri Mar 31 13:20:22 UTC 2017 x86_64 x86_64 x86_64 GNU/Linux

Can someone help me to investigate the problem, please


Update after solution was provided

I found that newly created route points to itself, using route command. Check exactly after pptp connected:

xxx.xxx.xxx.xxx 0.0.0.0         255.255.255.255 UH    50     0        0 ppp0

What I did is:

  1. Remove delete assigned address from network device
  2. Add back the assigned address along with a replacement peer address

Everything exactly as it was pointed in the link.

enter image description here

Finally I add this two steps into dispatcher.d script:

#!/bin/bash  

INTERFACE=$1
ACTION=$2
SSID="Your vpn connection name in Network Manager"

if [[ $CONNECTION_ID == "$SSID" ]]; then
        if [[ $ACTION = "vpn-up" ]]; then
                IP4_ADDRESS=$(ifconfig "$1" | grep -Eo 'inet (addr:)?([0-9]*\.){3}[0-9]*' | grep -Eo '([0-9]*\.){3}[0-9]*' | grep -v '127.0.0.1')
                ip addr del "$IP4_ADDRESS" dev $INTERFACE
                ip addr add "$IP4_ADDRESS" peer 192.168.1.9/24 dev $INTERFACE
        fi
fi

I put this script into /etc/NetworkManager/dispatcher.d

1
+50

Check this: http://pptpclient.sourceforge.net/howto-diagnosis.phtml#ip_loop.

NM (or pppd) is creating an additional, wrong, default route (even if nodefaultroute is being passed as parameter). route del won't delete it.

I got around it by telling NM the connection would be shared with other users.

It is most likely a bug, but this solved the problem for a while.

  • Thanks for the link, using it I found reliable solution. – c0rp May 7 '17 at 19:38

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