一、Linux?上的?PPP
Linux?中已經(jīng)包括了點對點協(xié)議PPP，其主體是?pppd?，如果你已經(jīng)使用過?Windows95?或?NT?的撥號網(wǎng)絡(luò)，
那么你已經(jīng)具備了?PPP?的基本經(jīng)驗了。在?Windows95?的?PPP?在同?ISP?連接后，視?ISP?情況不同，會自
動為?Windows?客戶機提供?IP?地址和?DNS?服務(wù)器地址，而?Linux?的?PPP?不會自動接收?DNS?地址，這是?
Linux?與?Windows?的一點區(qū)別，所以，Linux?上的?PPP?在協(xié)議連接成功后，要多一步?DNS?的配置。?
二、Kernel?的準備
你的?Linux?系統(tǒng)必須在?kernel?中配置支持?PPP?功能。如果你的?kernel?目前不支持?PPP，你需要重新生
成一個支持?PPP?的?kernel。重新編譯?kernel?的方法可看相關(guān)?Howto。?
三、用輔助腳本配置?PPP?撥號網(wǎng)絡(luò)
我一開始想運行?pppd?來連接撥號網(wǎng)絡(luò)，但很快發(fā)現(xiàn)這是太麻煩了，因為選項太多。后來我發(fā)現(xiàn)，其實在?
Linux?上已經(jīng)提供了幾個?PPP?撥號程序模版，只要對這些模板略作修改，就可輕松聯(lián)上?PPP?了。根據(jù)我
的經(jīng)驗，如果順利的話，10分鐘就能完成配置。?
（1）撥號程序所在的目錄?
對于?RedHat?5.0，這幾個撥號程序（Script）在?/usr/doc/ppp-2.2.0f/scripts?下，如果要使用這些腳本，
需要把它們拷貝到正確的目錄中，具體如下：?
ppp-on：?PPP?連接腳本?拷貝到?/usr/sbin?
ppp-off：?PPP?斷開腳本?拷貝到?/usr/sbin?
ppp-on-dialer：?PPP?登錄會話腳本?拷貝到?/etc/ppp?
ppp-redialer：?可輪循多個電話號碼的登陸腳本?拷貝到?/usr/sbin?（本文不用）?
對于?Slackware?的用戶，這些腳本已經(jīng)安裝到正確的目錄了，無需做什么。
假定你在你的系統(tǒng)上找不到上述文件，可直接在本文后面的附錄中cut。?
（2）創(chuàng)建自己的撥號程序?
假定現(xiàn)在我們要用?PPP?連接?163?網(wǎng)，我們就可以利用上述腳本來作很簡單的配置。雖然我們可以直接在這
些模板上做修改，我還是建議為自己拷貝一份模板，在新的拷貝上作修改比較好。所以，我們先做如下拷貝：?
cd?/usr/sbin
cp?ppp-on?ppp.163
chmod?+x?ppp.163
cd?/etc/ppp
cp?ppp-on-dialer?dialer.163
chmod?+x?dialer.163
此外，要保證?ppp-off?也是可執(zhí)行的?
（3）定制自己的撥號程序?
首先編輯你的?ppp.163，其中多數(shù)內(nèi)容都不必改動，只要修改以下幾處：?
TELEPHONE=163
ACCOUNT=
PASSWORD=
DIALER_SCRIPT=/etc/ppp/dialer.163
另外，在最后的?exec?啟動?pppd?一行里，注意提供你的?Modem?所在的串口設(shè)備文件（通常是
?COM1?/dev/cua0?或?/dev/ttyS0，COM2?/dev/cua1?或?/dev/ttyS1），并設(shè)置串口的通信速度（缺省是?38400，
?對于現(xiàn)在的高速?Modem，這個速度太低了，可設(shè)置成?57600以上）。完成后的?ppp.163?內(nèi)容是：?
#!/bin/sh
#
#?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=163?#?撥號號碼
ACCOUNT=YourUserName?#?用戶名?
PASSWORD=YourPassword?#?口令，注意限制其他人讀取本文件！
LOCAL_IP=0.0.0.0?#?本地IP地址，0.0.0.0?表示動態(tài)分配
REMOTE_IP=0.0.0.0?#?原端IP地址，一般是?0.0.0.0
NETMASK=255.255.255.0?#?子網(wǎng)掩碼
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?$PATH?variable?is?not
#?used?on?the?connect?option.?(To?do?so?on?a?'root'?account?would?be
#?a?security?hole?so?don't?ask.)
#
DIALER_SCRIPT=/etc/ppp/dialer.163?#?撥號登錄腳本文件名
#
#?Initiate?the?connection
#?
#?I?put?most?of?the?common?options?on?this?command.?Please,?don't
#?forget?the?'lock'?option?or?some?programs?such?as?mgetty?will?not
#?work.?The?asyncmap?and?escape?will?permit?the?PPP?link?to?work?with
#?a?telnet?or?rlogin?connection.?You?are?welcome?to?make?any?changes
#?as?desired.?Don't?use?the?'defaultroute'?option?if?you?currently
#?have?a?default?route?to?an?ethernet?gateway.
#
exec?/usr/sbin/pppd?debug?lock?modem?crtscts?/dev/ttycua0?57600?\
asyncmap?20A0000?escape?FF?kdebug?0?$LOCAL_IP:$REMOTE_IP?\
noipdefault?netmask?$NETMASK?defaultroute?connect?$DIALER_SCRIPT
然后，檢查一下你的登錄會話程序?/etc/ppp/dialer.163，在我所在的?163?ISP，這個從模板拷貝過來的
會話程序可直接使用，如果有以下情況，你需要對這個會話程序略作改動：?
（1）如果撥號提示輸入用戶名的提示符不是?login:?
（2）如果登錄成功后還要用戶再交互打入命令?，才啟動?ppp?協(xié)議
本文后面的附錄三是一個根據(jù)上述要求略加修改后的登錄腳本。?
建議：假如你有多個?ISP?可連接，就創(chuàng)建多個撥號?PPP?連接腳本和相應(yīng)的?PPP?登錄腳本。?
四、啟動?PPP?和斷開?PPP
啟動你的?PPP?連接唯一要做的就是開啟?Modem，運行剛才寫好的?ppp.163。你的?ppp.163?腳本將自動撥
號、送出登錄信息、完成協(xié)議認證，等你看到你的?Modem?上的數(shù)據(jù)傳輸指示燈不再閃動并保持連接狀態(tài)，
PPP?連接就完成了，你可以打命令：?
netstat?-r?
查看當前的路由表，如果?PPP?協(xié)議連接成功的話，路由表里就會有連接你的?ISP?的缺省路由。你的?PPP
?已經(jīng)配置成功了。?
如果沒有成功，注意看一下?/etc/ppp?下的?PPP?出錯記錄文件。?
要斷開?PPP?連接，運行?ppp-off。?
五、DNS?的配置
PPP?連接成功后，如果要使用?WWW?瀏覽器、Ftp、Telnet?等服務(wù)，必須正確配置?DNS?域名解析。所以，
一旦?PPP?連接完畢，應(yīng)該在?/etc/resolv.conf?中加入一行：?
nameserver??
注意?nameserver?后面的是你的?ISP?的?DNS?服務(wù)器的?IP?地址，并且這一行說明必須放在其他的?
nameserver?說明之前，否則，你的?Linux?系統(tǒng)不會訪問你的?ISP?的?DNS?服務(wù)器。然后，你就能使用各
項?Internet?服務(wù)了。?
六、自動配置?DNS?解析
本節(jié)內(nèi)容并不是配置?PPP?必需的，但能對?PPP?的使用提供一些方便。?
由于你的?Linux?并不總是連在?Internet?上，所以在不連接?PPP?時，需要的?resolv.conf?是不同的。
所以，我們希望有一種辦法能根據(jù)不同的情況，在?Linux?系統(tǒng)上自動設(shè)置合適的?resolv.conf?。?
在?/etc/ppp?下，有兩個根據(jù)?PPP?連接狀態(tài)自動運行的腳本，ip-up?和?ip-down，分別在?PPP?建立連接
和斷開連接時運行，如果用戶希望在?PPP?連接或斷開時執(zhí)行某些命令，可以在?/etc/ppp?目錄下建立腳
本文件?ip-up.local?和?ip-up.local，在這兩個文件中放入要執(zhí)行的命令。當?PPP?建立連接后，ip-up?
會調(diào)用?ip-up.local，執(zhí)行用戶命令；當?PPP?斷開連接后，ip-down?會調(diào)用?ip-down.local?，執(zhí)行用戶
命令。?
所以我們可以利用這個機制實現(xiàn)?DNS?解析的自動配置，方法如下：?
（1）在?/etc?下編輯分別適用于?PPP?連接狀態(tài)和正常本地狀態(tài)的?DNS?解析配置文件，我們假定這兩個
文件是?resolv.ppp?和?resolv.normal。?
（2）在?/etc/ppp?下建立?ip-up.local，設(shè)置其執(zhí)行權(quán)限，并在文件中加入：?
cp?/etc/resolv.ppp?/etc/resolv.conf?
（3）在?/etc/ppp?下建立?ip-down.local，設(shè)置其執(zhí)行權(quán)限，并在文件中加入：?
cp?/etc/resolv.normal?/etc/resolv.conf?
這樣設(shè)置后，每當?PPP?連接成功后，/etc/resolv.conf?的內(nèi)容就是?resolv.ppp，而?PPP?斷開后，
/etc/resolv.conf?被恢復(fù)成?resolv.normal?的內(nèi)容。?
附錄一：PPP?連接腳本模板?ppp-on
#!/bin/sh
#
#?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=555-1212?#?The?telephone?number?for?the?connection
ACCOUNT=george?#?The?account?name?for?logon
PASSWORD=gracie?#?The?password?for?this?account
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?don't?ask.)
#
DIALER_SCRIPT=/etc/ppp/ppp-on-dialer
#
#?Initiate?the?connection
#?
#?I?put?most?of?the?common?options?on?this?command.?Please,?don't
#?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.?Don't?use?the?'defaultroute'?option?if?you?currently
#?have?a?default?route?to?an?ethernet?gateway.
#
exec?/usr/sbin/pppd?debug?lock?modem?crtscts?/dev/ttyS0?38400?\
asyncmap?20A0000?escape?FF?kdebug?0?$LOCAL_IP:$REMOTE_IP?\
noipdefault?netmask?$NETMASK?defaultroute?connect?$DIALER_SCRIPT
附錄二：PPP?登錄腳本模板?ppp-on-dialer
#!/bin/sh
#
#?This?is?part?2?of?the?ppp-on?script.?It?will?perform?the?connection
#?protocol?for?the?desired?connection.
#
exec?chat?-v?\
TIMEOUT?3?\
ABORT?'\nBUSY\r'?\
ABORT?'\nNO?ANSWER\r'?\
ABORT?'\nRINGING\r\n\r\nRINGING\r'?\
''?\rAT?\
'OK-+++\c-OK'?ATH0?\
TIMEOUT?30?\
OK?ATDT$TELEPHONE?\
CONNECT?''?\
ogin:--ogin:?$ACCOUNT?\
assword:?$PASSWORD
附錄三：一個稍作修改的?PPP?登錄腳本
#!/bin/sh
#
#?This?is?part?2?of?the?ppp-on?script.?It?will?perform?the?connection
#?protocol?for?the?desired?connection.
#
exec?chat?-v?\
TIMEOUT?3?\
ABORT?'\nBUSY\r'?\
ABORT?'\nNO?ANSWER\r'?\
ABORT?'\nRINGING\r\n\r\nRINGING\r'?\
''?\rAT?\
'OK-+++\c-OK'?ATH0?\
TIMEOUT?30?\
OK?ATDT$TELEPHONE?\
CONNECT?''?\
sername:--sername:?$ACCOUNT?\
assword:?$PASSWORD?\
nnex:?ppp
說明：（1）用戶登錄提示符從由?login:?改為?username:?
（2）用戶登錄后，訪問服務(wù)器出現(xiàn)提示符?annex:?，需要手工輸入?ppp?命令?
附錄四：可輪詢撥號的?PPP?連接腳本模板?ppp-redialer
#!/bin/sh
###################################################################
#
#?These?parameters?control?the?attack?dialing?sequence.
#
#?Maximum?number?of?attempts?to?reach?the?telephone?number(s)
MAX_ATTEMPTS=10
#?Delay?between?each?of?the?attempts.?This?is?a?parameter?to?sleep
#?so?use?"15s"?for?15?seconds,?"1m"?for?1?minute,?etc.
SLEEP_DELAY=15s
###################################################################
#
#?This?is?a?list?of?telephone?numbers.?Add?new?numbers?if?you?wish
#?and?see?the?function?'callall'?below?for?the?dial?process.
PHONE1=555-1212
PHONE2=411
###################################################################
#
#?If?you?use?the?ppp-on?script,?then?these?are?passed?to?this?routine
#?automatically.?There?is?no?need?to?define?them?here.?If?not,?then
#?you?will?need?to?set?the?values.
#
ACCOUNT=my_account_name
PASSWORD=my_password
###################################################################
#
#?Function?to?initialize?the?modem?and?ensure?that?it?is?in?command
#?state.?This?may?not?be?needed,?but?it?doesn't?hurt.
#
function?initialize
{
chat?-v?TIMEOUT?3?''?AT?'OK-+++\c-OK'
return
}
###################################################################
#
#?Script?to?dial?a?telephone
#
function?callnumber
{
chat?-v?\
ABORT?'\nBUSY\r'?\
ABORT?'\nNO?ANSWER\r'?\
ABORT?'\nRINGING\r\n\r\nRINGING\r'?\
''?ATDT$1?\
CONNECT?''?\
ogin:--ogin:?$ACCOUNT?\
assword:?$PASSWORD
#
#?If?the?connection?was?successful?then?end?the?whole?script?with?a
#?success.
#
if?[?"$?"?=?"0"?];?then
exit?0
fi
return
}
###################################################################
#
#?Script?to?dial?any?telephone?number
#
function?callall
{
#?echo?"dialing?attempt?number:?$1"?>/dev/console
callnumber?$PHONE1
#?callnumber?$PHONE2
}
###################################################################
#
#?Initialize?the?modem?to?ensure?that?it?is?in?the?command?state
#
initialize
if?[?!?"$?"?=?"0"?];?then
exit?1
fi
#
#?Dial?telephone?numbers?until?one?answers
#
attempt=0
while?:?;?do
attempt=`expr?$attempt?+?1`
callall?$attempt
if?[?"$attempt"?=?"$MAX_ATTEMPTS"?];?then
exit?1
fi?
sleep?"$SLEEP_DELAY"
done
附錄五：PPP?斷開腳本?ppp-off
#!/bin/sh
######################################################################
#
#?Determine?the?device?to?be?terminated.
#
if?[?"$1"?=?""?];?then
DEVICE=ppp0
else
DEVICE=$1
fi
######################################################################
#
#?If?the?ppp0?pid?file?is?present?then?the?program?is?running.?Stop?it.
if?[?-r?/var/run/$DEVICE.pid?];?then
kill?-INT?`cat?/var/run/$DEVICE.pid`
#
#?If?the?kill?did?not?work?then?there?is?no?process?running?for?this
#?pid.?It?may?also?mean?that?the?lock?file?will?be?left.?You?may?wish
#?to?delete?the?lock?file?at?the?same?time.
if?[?!?"$?"?=?"0"?];?then
rm?-f?/var/run/$DEVICE.pid
echo?"ERROR:?Removed?stale?pid?file"
exit?1
fi
#
#?Success.?Let?pppd?clean?up?its?own?junk.
echo?"PPP?link?to?$DEVICE?terminated."
exit?0
fi
#
#?The?ppp?process?is?not?running?for?ppp0
echo?"ERROR:?PPP?link?is?not?active?on?$DEVICE"
exit?1
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