一．Linux與Linux之間的互拔：
請看圖一：
我家里： 辦公室：

機器名：j128 機器名：vms68
OS: RedHat5.1 OS: RedHat5.1
IP: 192.168.88.128 <----電話網----> IP: 192.168.89.68 <--->
Internet
| [ttyS0] [ttyS1] [ttyS0]
|網線
|
機器名：j003
OS: Win98
IP: 192.168.88.3

第一步要配置Linux為ppp服務器，允許拔入，如姚飛所說：

使用mgetty
(以下假設modem裝在ttyS0)

cd /etc
vi inittab

add :

d1:2345:respawn:/sbin/mgetty ttyS0 # COM1口允許拔入
d2:2345:respawn:/sbin/mgetty ttyS1 # COM2口允許拔入

then: init q # 重讀配置文件/etc/inittab

注意, 如果想拔號出去, pppd 使用的設備也必須是/dev/ttyS0或/dev/ttyS1,
而不是/dev/modem, 要不然是撥不出去的.

我這樣做后，j128和vms68都可允許拔入，但還不是ppp server，還需要以下幾步：
在vms68里：
adduser ppp #新加一個用戶
passwd ppp #為ppp起個密碼
在/home/ppp下建一個腳本ppplogin，內容如下：
exec /usr/sbin/pppd 115200 modem asyncmap 0 proxyarp \
192.168.89.68:192.193.89.69
##### LOCALIP:REMOTEIP
vi /etc/passwd
將這行ppp:xxxx:505:505:ppp acount:/home/ppp:/bin/bash
改為ppp:xxxx:505:505:ppp acount:/home/ppp:/home/ppp/ppplogin

在j128里：
adduser ppp #新加一個用戶
passwd ppp #為ppp起個密碼
在/home/ppp下建一個腳本ppplogin，內容如下：
exec /usr/sbin/pppd 115200 modem asyncmap 0 proxyarp \
0.0.0.0:0.0.0.0.0 ###等vms68分配ip地址
vi /etc/passwd
將這行ppp:xxxx:505:505:ppp acount:/home/ppp:/bin/bash
改為ppp:xxxx:505:505:ppp acount:/home/ppp:/home/ppp/ppplogin

下一步要配j128拔到vms68，這很簡單，
跟拔到Internet是一樣的，文件ppp-onvms68如下：
# script to initiate a ppp connection. This is the first part of the
# pair of scripts. This is not a secure pair of scripts as the codes
# are visible with the ps command. However, it is simple.
#
# These are the parameters. Change as needed.
TELEPHONE=xxxx # The telephone number for the connection
ACCOUNT=ppp # The account name for logon (as in George Burns)
PASSWORD=xxxx # The password for this account (and Gracie Allen)
LOCAL_IP=0.0.0.0 # Local IP address if known. Dynamic = 0.0.0.0
REMOTE_IP=0.0.0.0 # Remote IP address if desired. Normally 0.0.0.0
NETMASK=255.255.255.0 # The proper netmask if needed
#
# Export them so that they will be available at ppp-on-dialer time.
export TELEPHONE ACCOUNT PASSWORD
#
# This is the location of the script which dials the phone and logs
# in. Please use the absolute file name as the $PATH variable is not
# used on the connect option. (To do so on a root account would be
# a security hole so dont ask.)
#
DIALER_script=/home/ppp/ppp-on-dialer
#
# Initiate the connection
#
# I put most of the common options on this command. Please, dont
# forget the lock option or some programs such as mgetty will not
# work. The asyncmap and escape will permit the PPP link to work with
# a telnet or rlogin connection. You are welcome to make any changes
# as desired. Dont use the defaultroute option if you currently
# have a default route to an ethernet gateway.
#
exec /usr/sbin/pppd /dev/ttyS0 115200 modem $LOCAL_IP:$REMOTE_IP \
defaultroute lock crtscts asyncmap 0 connect $DIALER_script \
debug

現在配vms68拔到j128，文件ppp-onj128如下:
# script to initiate a ppp connection. This is the first part of the
# pair of scripts. This is not a secure pair of scripts as the codes
# are visible with the ps command. However, it is simple.
#
# These are the parameters. Change as needed.
TELEPHONE=xxxx # The telephone number for the connection
ACCOUNT=ppp # The account name for logon (as in George Burns)
PASSWORD=xxxx # The password for this account (and Gracie Allen)
LOCAL_IP=192.168.89.68 # Local IP address if known. Dynamic = 0.0.0.0
REMOTE_IP=192.168.89.69 # Remote IP address if desired. Normally 0.0.0.0
NETMASK=255.255.255.0 # The proper netmask if needed
#
# Export them so that they will be available at ppp-on-dialer time.
export TELEPHONE ACCOUNT PASSWORD
#
# This is the location of the script which dials the phone and logs
# in. Please use the absolute file name as the $PATH variable is not
# used on the connect option. (To do so on a root account would be
# a security hole so dont ask.)
#
DIALER_script=/home/ppp/ppp-on-dialer
#
# Initiate the connection
#
# I put most of the common options on this command. Please, dont
# forget the lock option or some programs such as mgetty will not
# work. The asyncmap and escape will permit the PPP link to work with
# a telnet or rlogin connection. You are welcome to make any changes
# as desired. Dont use the defaultroute option if you currently
# have a default route to an ethernet gateway.
#
exec /usr/sbin/pppd /dev/ttyS1 115200 modem $LOCAL_IP:$REMOTE_IP \
lock crtscts asyncmap 0 connect $DIALER_script \
debug

這里要注意LOCAL_IP和REMOTE_IP要給值，還有的是在pppd里沒有defaultroute。
因為vms68還要拔上Internet，所以不要defaultroute。

在j128上用ppp-onvms68拔上vms68，連通后telnet vms68，執行以下命令：
nohup sleep 30;ppp-onj128
然后在j128上斷線，等待vms68拔入。拔通后，在j128上要執行以下命令：
route add -net 192.168.89.0 gw 192.168.89.69 ppp0
route add default gw 192.168.89.69 ppp0
ipfwadm -F -a m -S 192.168.88.0/24 -D 0.0.0.0/0
現在可再telnet vms68，在vms68上拔號上網，這樣j003可通過j128，再通
過vms68上網，我也不用付任何費用。

二．Win98與Linux之間的互拔：
請看圖二：
我家里： 辦公室：

機器名：j128 機器名：vms68
OS: RedHat5.1 OS: RedHat5.1
IP: 192.168.88.128 IP: 192.168.89.68 <--->
Internet
| [ttyS1] [ttyS0]
|網線 |
| |
機器名：j003 |
OS: Win98 ---------------------------
IP: 192.168.88.3 電話網

這里vms68要象第一步所說的，要配成允許拔入的ppp server。
這里主要是win98的配置，首先象上Internet那樣，在拔號網絡里新建一個連接，
要注意兩點，一要設置連通后彈出終端窗口，二是最主要的，在“控制面板”里
選“調制解調器”，選用來連線的modem，選“屬性”按鈕，選“連接”，再選
“高級”按鈕，再在“附加設置”里輸入&C0S0=001。
為什么要這樣做？因為win98自帶的ppp client會自動退出當遠端ppp server掛線
時，因此要騙一騙win98，要modem不要報告斷線，并自動應答拔入。&C0就是要
modem不要檢測carrier，s0=001要modem在響一下后就應答。

現在配vms68拔到j003，文件ppp-onj003如下:
# script to initiate a ppp connection. This is the first part of the
# pair of scripts. This is not a secure pair of scripts as the codes
# are visible with the ps command. However, it is simple.
#
# These are the parameters. Change as needed.
TELEPHONE=xxxx # The telephone number for the connection
#ACCOUNT=ppp # The account name for logon (as in George Burns)
#PASSWORD=xxxx # The password for this account (and Gracie Allen)
LOCAL_IP=192.168.89.68 # Local IP address if known. Dynamic = 0.0.0.0
REMOTE_IP=192.168.89.69 # Remote IP address if desired. Normally 0.0.0.0
NETMASK=255.255.255.0 # The proper netmask if needed
#
# Export them so that they will be available at ppp-on-dialer time.
export TELEPHONE ###ACCOUNT PASSWORD
#
# This is the location of the script which dials the phone and logs
# in. Please use the absolute file name as the $PATH variable is not
# used on the connect option. (To do so on a root account would be
# a security hole so dont ask.)
#
DIALER_script=/home/ppp/ppp-on-dialer
#
# Initiate the connection
#
# I put most of the common options on this command. Please, dont
# forget the lock option or some programs such as mgetty will not
# work. The asyncmap and escape will permit the PPP link to work with
# a telnet or rlogin connection. You are welcome to make any changes
# as desired. Dont use the defaultroute option if you currently
# have a default route to an ethernet gateway.
#
exec /usr/sbin/pppd /dev/ttyS1 115200 modem $LOCAL_IP:$REMOTE_IP \
lock crtscts asyncmap 0 connect $DIALER_script \
debug

這里要注意LOCAL_IP和REMOTE_IP要給值，還有的是在pppd里沒有defaultroute。
因為vms68還要拔上Internet，所以不要defaultroute。還有這里沒有ACOUNT和
PASSWORD，因為WIN98的PPP CLIENT不要用戶名和密碼，因此在PPP-ON-DIALER里
要把送ACOUNT和PASSWORD的那兩行去掉。
J003通過拔號拔上VMS68后，要TELNET VMS68，在VMS68里執行以下腳本：
kill `cat /var/run/ppp0.pid` ###注意如果是用ppp1，就用ppp1.pid
nohup sleep 30;ppp-onj003
這里要特別注意的一點是一定要在linux里斷線，因為在WIN98里斷線，則WIN98
的PPP CLIENT就會退出，就不會應答呼叫。

現在WIN98和LINUX之間就可以實現回拔了，但要注意WIN98的路由問題。

在win98下要自配一下路由，在win98的目錄里有route程序，它的格式如下：
route print/add/delete/change (直接打route就有幫助看)

象我的j003，在沒有拔號時，用route print得到如下信息：(行號是我加上的)
Active Routes:

Network Address Netmask Gateway Address Interface Metric
1 0.0.0.0 0.0.0.0 192.168.88.128 192.168.88.3 1
2 127.0.0.0 255.0.0.0 127.0.0.1 127.0.0.1 1
3 192.168.88.0 255.255.255.0 192.168.88.3 192.168.88.3 1
4 192.168.88.3 255.255.255.255 127.0.0.1 127.0.0.1 1
5 192.168.88.255 255.255.255.255 192.168.88.3 192.168.88.3 1
6 224.0.0.0 224.0.0.0 192.168.88.3 192.168.88.3 1
7 255.255.255.255 255.255.255.255 192.168.88.3 0.0.0.0 1

通過拔號網絡拔入vms68后，用route print得到如下信息：

Active Routes:

Network Address Netmask Gateway Address Interface Metric
1* 0.0.0.0 0.0.0.0 192.168.89.69 192.168.89.69 1
2* 0.0.0.0 0.0.0.0 192.168.88.128 192.168.88.3 2
3 127.0.0.0 255.0.0.0 127.0.0.1 127.0.0.1 1
4 192.168.88.0 255.255.255.0 192.168.88.3 192.168.88.3 2
5 192.168.88.3 255.255.255.255 127.0.0.1 127.0.0.1 1
6 192.168.88.255 255.255.255.255 192.168.88.3 192.168.88.3 1
7 192.168.89.0 255.255.255.0 192.168.89.69 192.168.89.69 1
8 192.168.89.69 255.255.255.255 127.0.0.1 127.0.0.1 1
9 224.0.0.0 224.0.0.0 192.168.88.3 192.168.88.3 1
10 224.0.0.0 224.0.0.0 192.168.89.69 192.168.89.69 1
11 255.255.255.255 255.255.255.255 192.168.89.69 192.168.89.69 1
注意我打＊號的地方，從WIN98拔號到LINUX，WIN98會自動配置路由，從LINUX拔號到WIN98?
?
WIN98就得手工配置路由，打＊號的就是要在LINUX拔號到WIN98時要手工加上的。

現在TELNET上VMS68執行回拔腳本，連通后用route print得到如下信息：

Active Routes:

Network Address Netmask Gateway Address Interface Metric
1 0.0.0.0 0.0.0.0 192.168.88.128 192.168.88.3 1
2 127.0.0.0 255.0.0.0 127.0.0.1 127.0.0.1 1
3 192.168.88.0 255.255.255.0 192.168.88.3 192.168.88.3 1
4 192.168.88.3 255.255.255.255 127.0.0.1 127.0.0.1 1
5 192.168.88.255 255.255.255.255 192.168.88.3 192.168.88.3 1
6 192.168.89.0 255.255.255.0 192.168.89.69 192.168.89.69 1
7 192.168.89.69 255.255.255.255 127.0.0.1 127.0.0.1 1
8 224.0.0.0 224.0.0.0 192.168.89.69 192.168.89.69 1
9 224.0.0.0 224.0.0.0 192.168.88.3 192.168.88.3 1
10 255.255.255.255 255.255.255.255 192.168.89.69 192.168.89.69 1
現在可看到跟上面的不同了，要在WIN98的DOS窗口下執行以下批處理：
route change 0.0.0.0 mask 0.0.0.0 192.168.88.128 metric 2
route add 0.0.0.0 mask 0.0.0.0 192.168.89.69

現在再用route print就會得到如下信息：
.
Active Routes:

Network Address Netmask Gateway Address Interface Metric
1 0.0.0.0 0.0.0.0 192.168.89.69 192.168.89.69 1
2 0.0.0.0 0.0.0.0 192.168.88.128 192.168.88.3 2
3 127.0.0.0 255.0.0.0 127.0.0.1 127.0.0.1 1
4 192.168.88.0 255.255.255.0 192.168.88.3 192.168.88.3 1
5 192.168.88.3 255.255.255.255 127.0.0.1 127.0.0.1 1
6 192.168.88.255 255.255.255.255 192.168.88.3 192.168.88.3 1
7 192.168.89.0 255.255.255.0 192.168.89.69 192.168.89.69 1
8 192.168.89.69 255.255.255.255 127.0.0.1 127.0.0.1 1
9 224.0.0.0 224.0.0.0 192.168.88.3 192.168.88.3 1
10 224.0.0.0 224.0.0.0 192.168.89.69 192.168.89.69 1
11 255.255.255.255 255.255.255.255 192.168.89.69 192.168.89.69 1

現在可TELNET上VMS68，在VMS68上拔號到INTERNET，現在J003可通過VMS68上網了。

一些不足的地方：
一．要手工的地方太多，不大方便，請朋友們再改良一下。
二．只能用兩個串口，我沒有玩過多用戶卡，請有經驗的朋友指點一下在LINUX下用那種多用戶卡最好，在那有賣，多少錢

關鍵字：拔號、服務器、IP