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一、操作环境：
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机器系统与配置：三台机器的关健部件
第一台：台式机，双网卡，8139和8029，操作系统RedHat 8.0
第二台：Toshiba notebook，PC卡。RTL-8139/8139C/8139C+，操作系统RedHat 8.0
- m" U* ~) [( W4 B6 E. [第三台：台式机,8029网卡，操作系统windowme
Hub[集线器]：Tp-Link 10M，8口
ADSL，乙太口，非路由。
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二、网卡设置如下：
! Z# E3 e8 g$ ~" e) Q' ?在第一台机器的双网卡的接法：把ADSL接在eth0上，把eth1接在HUB上。
# i4 D& a+ F9 Y$ p1 B第一块网卡的ip设置：
ip地址:192.168.0.1
掩码:255.255.255.0
8 u/ M! Z% @! r/ L1 `2 R第二块网卡的设置
ip地址:192.168.0.2
! c, `* D% m; s8 K' L+ D+ X掩码：255.255.255.0
5 F* ]3 a" F3 y6 T! Y2 p0 Z在这两块网卡中，不要设置网关。
0 q0 _9 H+ K, G++++++++++++++++++++++++++++++++++++++++
. n) b4 c. M. U% \第二台：Toshiba notebook的网卡设置
IP：192.168.0.6
( w5 b' \3 J/ _9 m掩码：255.255.255.0
网关：192.168.0.1
DNS:设置电信给的，或者下面的也行
202.96.134.133
6 J: i# W/ s) M% f( P+ H  C- ^) P/ v202.96.168.68
8 c% j0 a5 A" g' \6 @. x: q/ _. ^, Z7 g++++++++++++++++++++++++++++++++++++++++
4 u! ~' [% k: F" G4 F& P/ V) u第三台机器的网卡设置
+ x$ h6 [# J: n' O6 H7 e. |P：192.168.0.8
# K' F( K4 E, _& ~% I' f掩码：255.255.255.0
网关：192.168.0.1
) @: Y/ a; m3 Q! a. yDNS:设置电信给的，或者下面的也行
9 C3 ]) ~7 p# p$ E1 ~4 G: O202.96.134.133
' Z7 O* F* f! k7 a* [, J' |202.96.168.68
三、设置ppp拔号，
1]删除原来的ppp的ADSL链接。
如果redhat-config-network原来已经用 redhat-config-network设置的ppp的ADSL连接拔号，用下面的命令调用删除。
#redhat-config-network

  U3 |2 [( u: c) G5 r# ?( ^6 F2]在终端上以root权限运行
#adsl-setup
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[root@LinuxSir02 root]# adsl-setup

; p  q' p$ s' {7 l- ?  h8 g. o0 {Welcome to the ADSL client setup. First, I will run some checks on
your system to make sure the PPPoE client is installed properly...

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LOGIN NAME
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Enter your Login Name (default root): ADSL提供商给的用户名，写在这里
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INTERFACE

Enter the Ethernet interface connected to the ADSL modem
For Solaris, this is likely to be something like /dev/hme0.
For Linux, it will be ethX, where 'X' is a number.
7 s, h0 t+ M5 a( r8 g) v3 i% Y(default eth0): eth0这是ADSL通过第一台机器的第一张网卡eth0提供上网
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Do you want the link to come up on demand, or stay up continuously?
If you want it to come up on demand, enter the idle time in seconds
after which the link should be dropped. If you want the link to
stay up permanently, enter 'no' (two letters, lower-case.)
NOTE: Demand-activated links do not interact well with dynamic IP
addresses. You may have some problems with demand-activated links.
% H9 ~" v: X* q, x/ ?/ F/ HEnter the demand value (default no):在这里按一下回车就行了。
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DNS
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: g/ W( g, y7 lPlease enter the IP address of your ISP's primary DNS server.
/ O7 Q: A; F  {! b, E/ g3 s& J& eIf your ISP claims that 'the server will provide dynamic DNS addresses',
3 j6 y& c6 Y* @enter 'server' (all lower-case) here.
If you just press enter, I will assume you know what you are
: V1 f- a* }4 N* |: Kdoing and not modify your DNS setup.
Enter the DNS information here: 202.96.134.133这是DSN，最好用你本地电信给的
Please enter the IP address of your ISP's secondary DNS server.
If you just press enter, I will assume there is only one DNS server.
( u! }$ c0 S$ pEnter the secondary DNS server address here: 202.96.168.68这是第二个DNS，也是电信给的。

PASSWORD
5 U9 d  f% a( I& Q& x. q( i  s" U
; ?/ E' W: w, uPlease enter your Password:在这里把ADSL提供商给的密码写上
Please re-enter your Password:

) O9 R) R6 d2 IUSERCTRL

Please enter 'yes' (two letters, lower-case.) if you want to allow
normal user to start or stop DSL connection (default yes): yes

8 Q/ h0 y- ?4 u& YFIREWALLING

Please choose the firewall rules to use. Note that these rules are
very basic. You are strongly encouraged to use a more sophisticated
' s* b, ]- T" G7 ], L+ ]firewall setup; however, these will provide basic security. If you
+ E$ ?: g/ J- K* ]6 r" uare running any servers on your machine, you must choose 'NONE' and
set up firewalling yourself. Otherwise, the firewall rules will deny
access to all standard servers like Web, e-mail, ftp, etc. If you
are using SSH, the rules will block outgoing SSH connections which
1 v. x# ?$ v. x, O* Oallocate a privileged source port.

The firewall choices are:
0 - NONE: This script will not set any firewall rules. You are responsible
for ensuring the security of your machine. You are STRONGLY
6 ?+ Y9 w; }" c9 B% C/ Trecommended to use some kind of firewall rules.
1 - STANDALONE: Appropriate for a basic stand-alone web-surfing workstation
2 - MASQUERADE: Appropriate for a machine acting as an Internet gateway
+ S  X+ @2 J$ U8 cfor a LAN
8 i: }* v# W3 ?) n1 oChoose a type of firewall (0-2): 2
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; i* ^8 X1 `* x2 L+ D' l  V) j; YStart this connection at boot time

Do you want to start this connection at boot time?
8 J1 [; n, B. @* L+ |# t# u1 _Please enter no or yes (default no):yes

& `  q4 S6 j* R** Summary of what you entered **

5 M/ G9 v; B3 p* ^- x! P% c% jEthernet Interface: eth0
; b% z2 H9 ?( ?/ [User name: ADSL用户名
8 P. K' V) g& NActivate-on-demand: No
Primary DNS: 202.96.134.133
* ]: F# W* m' `( z% Q  `Secondary DNS: 202.96.168.68
' v6 A4 e) p- a3 nFirewalling: MASQUERADE
User Control: yes
Accept these settings and adjust configuration files (y/n)?y
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三、在/etc/rc.d/rc.local中加入如下：

echo 1 > /proc/sys/net/ipv4/ip_forward
iptables -t nat -A POSTROUTING -s 192.168.0.0/24 -o ppp0 -j MASQUERADE

四、重新启动机器。就OK了。这有多简单