7.15. ( MTU ) - IP MASQ 似乎工作正常，但有些网站无法访问。这通常发生在 WWW 和一些 FTP 站点上。

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1. The setting of MTU can vary from Linux distribution to distribution.  

   For Redhat: You need to edit the various "ifconfig" statements in 
               the /sbin/ifup script

   For Slackware: You need to edit the various "ifconfig" statements in 
                  the /etc/rc.d/rc1.inet

2. Here is one good, any-distribution-will-work example, edit the 
   /etc/rc.d/rc.local file and put the following at the END of the file: 

        echo "Changing the MTU of ETH0"
        /sbin/ifconfig eth0 mtu 1492

     Replace "eth0" with the interface name that is the machine's upstream 
     connection which is connected to the Internet.

3. For advanced options like "TCP Receive Windows" and such, detailed examples
   on how to edit the respective networking scripts for your specific Linux
   distro, etc., please see Chapter 16 of 
   http://www.ecst.csuchico.edu/~dranch/LINUX/index-linux.html#trinityos 
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1. Making ANY changes to the Registry is inheritantly risky but
   with a backup copy, you should be safe.  Proceed at your 
   OWN RISK.

2. Goto Start-->Run-->RegEdit

3. Registry-->Export Registry File-->Save a copy of your registry
   to a reliable place

4. Navigate down to the key:

   [HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Services\Tcpip\Parameters\Inter
faces\<ID for Adapter>

   Each ID Adapter has default keys for DNS, TCP/IP address, Default Gateway, 
   subnet mask, etc. Find the key one that is for your network card.

5. Create the following Entry:

      type=DWORD
      name="MTU"				(Do NOT include the quotes)
      value=1492 (Decimal)      (Do NOT include the text "(Decimal)")

http://support.microsoft.com/support/kb/articles/Q120/6/42.asp?LN=EN-US&SD=gn&FR=0


 *** If you know how to also change the MSS, TCP Window Size, and the
 *** TTL parameters in NT 2000, please email dranch@trinnet.net as I 
 *** would love to add it to the HOWTO.

5. Reboot to let the changes take effect.
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------------------------------------------
1. Making ANY changes to the Registry is inheritantly risky but
   with a backup copy, you should be safe.  Proceed at your 
   OWN RISK.

2. Goto Start-->Run-->RegEdit

3. Registry-->Export Registry File-->Save a copy of your registry
   to a reliable place

4. Create the following keys in the Registry trees, choose two
   possible Registry trees.  Multiple entries are for various 
   network devices like DialUp Networking (ppp), Ethernet NICs, 
   PPTP VPNs, etc.

   http://support.microsoft.com/support/kb/articles/Q102/9/73.asp?LN=EN-US&SD=gn&FR=0


   [HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Services\Parameters\Tcpip]
                     and
   [HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Services\<Adapter-name>\Parameters\Tcpip]

      Replace "<Adapter-Name>" with the respective name of your uplink LAN NIC 
      interface

         type=DWORD
         name="MTU"              (Do NOT include the quotes)
         value=1492 (Decimal)    (Do NOT include the text "(Decimal>")

       (Do NOT include the quotes)


 *** If you know how to also change the MSS, TCP Window Size, and the
 *** TTL parameters in NT 4.x, please email dranch@trinnet.net as I 
 *** would love to add it to the HOWTO.

5. Reboot to make the changes take effect.
------------------------------------------

------------------------------------------
1. Making ANY changes to the Registry is inheritantly risky but
   with a backup copy, you should be safe.  Proceed at your OWN RISK.

2. Goto Start-->Run-->RegEdit

3. You should make a backup copy of your Registry before doing anything.  To
   do this, copy the "user.dat" and "system.dat" files from the \WINDOWS 
   directory and put them into a safe place.  It should be noted that the
   previously mentioned method of using "Regedit: Registry-->Export Registry 
   File-->Save a copy of your registry" would only perform Registry MERGES 
   and NOT do a replacement.

4. Search though each of the Registry trees that end in "n" (e.g. 0007) 
   and have a Registry entry called "IPAddress" which has the IP address
   of your NIC.  Under that key, add the following:

   From http://support.microsoft.com/support/kb/articles/q158/4/74.asp

     [Hkey_Local_Machine\System\CurrentControlset\Services\Class\NetTrans\000n]
         type=STRING
         name="MaxMTU"            (Do NOT include the quotes)
         value=1492 (Decimal)     (Do NOT include the text "(Decimal)")


5. You can also change the "TCP Receive Window" which sometimes
   increases network performance SUBSTANTIALLY.  If you notice your
   throughput has DECREASED, put these items BACK to their original 
   settings and reboot.

     [HKEY_LOCAL_MACHINE\System\CurrentControlSet\Services\VxD\MSTCP]

        type=STRING
        name="DefaultRcvWindow"    (Do NOT include the quotes)
        value=32768 (Decimal)      (Do NOT include the text "(Decimal>")

        type=STRING
        name="DefaultTTL"          (Do NOT include the quotes)
        value=128 (Decimal)        (Do NOT include the text "(Decimal>")


6. Reboot to let the changes take effect.
------------------------------------------

------------------------------------------
1. Making ANY changes to the Registry is inheritantly risky but
   with a backup copy, you should be safe.  Proceed at your OWN RISK.

2. Goto Start-->Run-->RegEdit

3. You should make a backup copy of your Registry before continuing.  To
   do this, copy the "user.dat" and "system.dat" files from the \WINDOWS 
   directory and put them into a safe place.  It should be noted that the
   previously mentioned method of using "Regedit: Registry-->Export Registry 
   File-->Save a copy of your registry" would only do Registry MERGES and NOT 
   do a replacement.

4. Search through each of the Registry trees that end in "n" (e.g. 0007) 
   and have a Registry entry called "IPAddress", which has the IP address
   of your NIC.  Under that key, add the following:

   From http://support.microsoft.com/support/kb/articles/q158/4/74.asp

     [Hkey_Local_Machine\System\CurrentControlset\Services\Class\NetTrans\000n]

         type=DWORD
         name="MaxMTU"           (Do NOT include the quotes)
         value=1492 (Decimal)    (Do NOT include the text "(Decimal)")

         type=DWORD
         name="MaxMSS"           (Do NOT include the quotes)
         value=1450 (Decimal)    (Do NOT include the text "(Decimal>")


5. You can also change the "TCP Receive Window" which sometimes
   increases network performance SUBSTANTIALLY.  If you notice your
   throughput has DECREASED, put these items BACK to their original 
   settings and reboot.

     [HKEY_LOCAL_MACHINE\System\CurrentControlSet\Services\VxD\MSTCP]
        type=DWORD
        name="DefaultRcvWindow"   (Do NOT include the quotes)
        value=32768 (Decimal)     (Do NOT include the text "(Decimal>")

        type=DWORD
        name="DefaultTTL"         (Do NOT include the quotes)
        value=128 (Decimal)       (Do NOT include the text "(Decimal>")


6. Reboot to let the changes take effect.
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