我在 centos 6 64 位服务器上安装了 pptp 服务器
PPTP 服务器 IP：55.66.77.10
PPTP 本地 IP：10.0.0.1
客户端1 IP：10.0.0.60 Centos5 64位
客户端2 IP：10.0.0.61 Centos5 64位
PPTP 服务器可以 ping客户端1和客户端1可以 pingPPTP 服务器
PPTP 服务器可以 ping客户端2和客户端2可以 pingPPTP 服务器
问题是客户端 1 无法 ping 通客户端 2，我在 PPTP 服务器错误日志中也收到此错误Cannot determine ethernet address for proxy ARP
从客户端 2 ping 客户端 1
PING 10.0.0.60 (10.0.0.60) 56(84) bytes of data.
--- 10.0.0.60 ping statistics ---
6 packets transmitted, 0 received, 100% packet loss, time 5000ms
PPTP 服务器上的 route -n
Destination Gateway Genmask Flags Metric Ref Use Iface
10.0.0.60 0.0.0.0 255.255.255.255 UH 0 0 0 ppp0
10.0.0.61 0.0.0.0 255.255.255.255 UH 0 0 0 ppp1
55.66.77.10 0.0.0.0 255.255.255.248 U 0 0 0 eth0
10.0.0.0 0.0.0.0 255.0.0.0 U 0 0 0 eth0
0.0.0.0 55.66.77.19 0.0.0.0 UG 0 0 0 eth0
客户端 1 上的 route -n
Destination Gateway Genmask Flags Metric Ref Use Iface
10.0.0.1 0.0.0.0 255.255.255.255 UH 0 0 0 ppp0
55.66.77.10 70.14.13.19 255.255.255.255 UGH 0 0 0 eth0
10.0.0.0 0.0.0.0 255.0.0.0 U 0 0 0 eth1
0.0.0.0 70.14.13.19 0.0.0.0 UG 0 0 0 eth0
客户端 2 上的 route -n
Destination Gateway Genmask Flags Metric Ref Use Iface
10.0.0.1 0.0.0.0 255.255.255.255 UH 0 0 0 ppp0
55.66.77.10 84.56.120.60 255.255.255.255 UGH 0 0 0 eth1
10.0.0.0 0.0.0.0 255.0.0.0 U 0 0 0 eth0
0.0.0.0 84.56.120.60 0.0.0.0 UG 0 0 0 eth1
在 PPTP 服务器上 cat /etc/ppp/options.pptpd
###############################################################################
# $Id: options.pptpd,v 1.11 2005/12/29 01:21:09 quozl Exp $
#
# Sample Poptop PPP options file /etc/ppp/options.pptpd
# Options used by PPP when a connection arrives from a client.
# This file is pointed to by /etc/pptpd.conf option keyword.
# Changes are effective on the next connection. See "man pppd".
#
# You are expected to change this file to suit your system. As
# packaged, it requires PPP 2.4.2 and the kernel MPPE module.
###############################################################################
# Authentication
# Name of the local system for authentication purposes
# (must match the second field in /etc/ppp/chap-secrets entries)
name pptpd
# Strip the domain prefix from the username before authentication.
# (applies if you use pppd with chapms-strip-domain patch)
#chapms-strip-domain
# Encryption
# (There have been multiple versions of PPP with encryption support,
# choose with of the following sections you will use.)
# BSD licensed ppp-2.4.2 upstream with MPPE only, kernel module ppp_mppe.o
# {{{
refuse-pap
refuse-chap
refuse-mschap
# Require the peer to authenticate itself using MS-CHAPv2 [Microsoft
# Challenge Handshake Authentication Protocol, Version 2] authentication.
require-mschap-v2
# Require MPPE 128-bit encryption
# (note that MPPE requires the use of MSCHAP-V2 during authentication)
require-mppe-128
# }}}
# OpenSSL licensed ppp-2.4.1 fork with MPPE only, kernel module mppe.o
# {{{
#-chap
#-chapms
# Require the peer to authenticate itself using MS-CHAPv2 [Microsoft
# Challenge Handshake Authentication Protocol, Version 2] authentication.
#+chapms-v2
# Require MPPE encryption
# (note that MPPE requires the use of MSCHAP-V2 during authentication)
#mppe-40 # enable either 40-bit or 128-bit, not both
#mppe-128
#mppe-stateless
# }}}
# Network and Routing
# If pppd is acting as a server for Microsoft Windows clients, this
# option allows pppd to supply one or two DNS (Domain Name Server)
# addresses to the clients. The first instance of this option
# specifies the primary DNS address; the second instance (if given)
# specifies the secondary DNS address.
#ms-dns 10.0.0.1
#ms-dns 10.0.0.2
# If pppd is acting as a server for Microsoft Windows or "Samba"
# clients, this option allows pppd to supply one or two WINS (Windows
# Internet Name Services) server addresses to the clients. The first
# instance of this option specifies the primary WINS address; the
# second instance (if given) specifies the secondary WINS address.
#ms-wins 10.0.0.3
#ms-wins 10.0.0.4
# Add an entry to this system's ARP [Address Resolution Protocol]
# table with the IP address of the peer and the Ethernet address of this
# system. This will have the effect of making the peer appear to other
# systems to be on the local ethernet.
# (you do not need this if your PPTP server is responsible for routing
# packets to the clients -- James Cameron)
proxyarp
# Normally pptpd passes the IP address to pppd, but if pptpd has been
# given the delegate option in pptpd.conf or the --delegate command line
# option, then pppd will use chap-secrets or radius to allocate the
# client IP address. The default local IP address used at the server
# end is often the same as the address of the server. To override this,
# specify the local IP address here.
# (you must not use this unless you have used the delegate option)
#10.8.0.100
# Logging
# Enable connection debugging facilities.
# (see your syslog configuration for where pppd sends to)
debug
# Print out all the option values which have been set.
# (often requested by mailing list to verify options)
#dump
# Miscellaneous
# Create a UUCP-style lock file for the pseudo-tty to ensure exclusive
# access.
lock
# Disable BSD-Compress compression
nobsdcomp
# Disable Van Jacobson compression
# (needed on some networks with Windows 9x/ME/XP clients, see posting to
# poptop-server on 14th April 2005 by Pawel Pokrywka and followups,
# http://marc.theaimsgroup.com/?t=111343175400006&r=1&w=2 )
novj
novjccomp
# turn off logging to stderr, since this may be redirected to pptpd,
# which may trigger a loopback
nologfd
# put plugins here
# (putting them higher up may cause them to sent messages to the pty)
在 Client1 和 Client2 上执行 cat /etc/ppp/options.pptp
###############################################################################
# $Id: options.pptp,v 1.3 2006/03/26 23:11:05 quozl Exp $
#
# Sample PPTP PPP options file /etc/ppp/options.pptp
# Options used by PPP when a connection is made by a PPTP client.
# This file can be referred to by an /etc/ppp/peers file for the tunnel.
# Changes are effective on the next connection. See "man pppd".
#
# You are expected to change this file to suit your system. As
# packaged, it requires PPP 2.4.2 or later from http://ppp.samba.org/
# and the kernel MPPE module available from the CVS repository also on
# http://ppp.samba.org/, which is packaged for DKMS as kernel_ppp_mppe.
###############################################################################
# Lock the port
lock
# Authentication
# We don't need the tunnel server to authenticate itself
noauth
# We won't do PAP, EAP, CHAP, or MSCHAP, but we will accept MSCHAP-V2
# (you may need to remove these refusals if the server is not using MPPE)
refuse-pap
refuse-eap
refuse-chap
refuse-mschap
# Compression
# Turn off compression protocols we know won't be used
nobsdcomp
nodeflate
# Encryption
# (There have been multiple versions of PPP with encryption support,
# choose which of the following sections you will use. Note that MPPE
# requires the use of MSCHAP-V2 during authentication)
#
# Note that using PPTP with MPPE and MSCHAP-V2 should be considered
# insecure:
# http://marc.info/?l=pptpclient-devel&m=134372640219039&w=2
# https://github.com/moxie0/chapcrack/blob/master/README.md
# http://technet.microsoft.com/en-us/security/advisory/2743314
# http://ppp.samba.org/ the PPP project version of PPP by Paul Mackarras
# ppp-2.4.2 or later with MPPE only, kernel module ppp_mppe.o
# If the kernel is booted in FIPS mode (fips=1), the ppp_mppe.ko module
# is not allowed and PPTP-MPPE is not available.
# {{{
# Require MPPE 128-bit encryption
#require-mppe-128
# }}}
# http://mppe-mppc.alphacron.de/ fork from PPP project by Jan Dubiec
# ppp-2.4.2 or later with MPPE and MPPC, kernel module ppp_mppe_mppc.o
# {{{
# Require MPPE 128-bit encryption
#mppe required,stateless
# }}}
IPtables在客户端和服务器上已停止，但net.ipv4.ip_forward = 1在 PPTP 服务器上也已启用。
我怎么解决这个问题 。？
答案1
您的 pptp 客户端上的网络掩码错误...这些是点对点链接，因此请在 pptp 选项中设置网络掩码 255.255.255.255。执行此操作后，客户端将使用指向 pptp 服务器的默认网络掩码。
现在出现这种情况的原因是客户端认为可以通过 ARP 相互访问（因为它们都在 10.0.0.0/255.0.0.0 网络上）；但是 pptp 没有可用的 mac 地址。