在酒店(杭州宾江速8)里gentoo安装ppp,总是emerge失败。但是ping 站点成功得一踏糊涂。考虑到host系统中打开网页时开时不开。因此,怀疑tcp mss问题。  
  
   gentoo中修改mtu, ifconfig eth0 mtu 1024.竟然问题解决。
  
   就想协助酒店改一下路由器配置,http路由器,发现是 TP-LINK Router R860.

   唉,这破东西竟然不是缺省密码,暴力破解太费时间。算了。

   写在这里,大家借鉴。

   另外,windows 修改Mtu要改一个注册表项:
   HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Services\Tcpip\Parameters\Interfaces。
   其中新建一个注册表项 MTU,赋其值为合适即可。
==============
  刚好要安装另一台gentoo虚拟机,补充一些信息:
  无法emerge:
  emerge ppp
Calculating dependencies... done!
>>> Verifying ebuild Manifests...

>>> Emerging (1 of 1) net-dialup/ppp-2.4.4-r21 to /
>>> Downloading 'http://distfiles.gentoo.org/distfiles/ppp-2.4.4.tar.gz'
--12:00:02--  [url]http://distfiles.gentoo.org/distfiles/ppp-2.4.4.tar.gz[/url]
           => `/usr/portage/distfiles/ppp-2.4.4.tar.gz'
Resolving distfiles.gentoo.org... 64.50.238.52, 64.50.236.52, 216.165.129.135, ...
Connecting to distfiles.gentoo.org|64.50.238.52|:80... connected.
HTTP request sent, awaiting response... Read error (Connection timed out) in headers.
Retrying.

--12:01:04--  [url]http://distfiles.gentoo.org/distfiles/ppp-2.4.4.tar.gz[/url]
  (try: 2) => `/usr/portage/distfiles/ppp-2.4.4.tar.gz'
Connecting to distfiles.gentoo.org|64.50.238.52|:80... connected.
HTTP request sent, awaiting response... Read error (Connection timed out) in headers.
Retrying.

--12:02:06--  [url]http://distfiles.gentoo.org/distfiles/ppp-2.4.4.tar.gz[/url]
  (try: 3) => `/usr/portage/distfiles/ppp-2.4.4.tar.gz'
Connecting to distfiles.gentoo.org|64.50.238.52|:80... connected.
HTTP request sent, awaiting response...
=================
小包ping大包不通:
rt2 ~ # ping  distfiles.gentoo.org
PING distfiles.gentoo.org (140.211.166.134) 56(84) bytes of data.
64 bytes from ftp-osl.osuosl.org (140.211.166.134): icmp_seq=1 ttl=47 time=580 ms
64 bytes from ftp-osl.osuosl.org (140.211.166.134): icmp_seq=2 ttl=47 time=576 ms
64 bytes from ftp-osl.osuosl.org (140.211.166.134): icmp_seq=3 ttl=47 time=582 ms
^C
--- distfiles.gentoo.org ping statistics ---
3 packets transmitted, 3 received, 0% packet loss, time 4532ms
rtt min/avg/max/mdev = 576.722/579.626/582.019/2.192 ms
rt2 ~ # ping  distfiles.gentoo.org -s 1400
PING distfiles.gentoo.org (156.56.247.195) 1400(1428) bytes of data.
From 10.0.2.1 icmp_seq=1 Frag needed and DF set (mtu = 1400)
---------------
配置mtu
rt2 ~ # ifconfig eth0 mtu 1024
---------------
再次emerge, 这下小河流水哗啦啦了:
rt2 ~ # emerge ppp
Calculating dependencies... done!
>>> Verifying ebuild Manifests...

>>> Emerging (1 of 1) net-dialup/ppp-2.4.4-r21 to /
>>> Downloading 'http://distfiles.gentoo.org/distfiles/ppp-2.4.4.tar.gz'
--12:06:06--  [url]http://distfiles.gentoo.org/distfiles/ppp-2.4.4.tar.gz[/url]
           => `/usr/portage/distfiles/ppp-2.4.4.tar.gz'
Resolving distfiles.gentoo.org... 64.50.238.52, 64.50.236.52, 216.165.129.135, ...
Connecting to distfiles.gentoo.org|64.50.238.52|:80... connected.
HTTP request sent, awaiting response... 200 OK
Length: 688,763 (673K) [application/x-gzip]

100%[===========================================================>] 688,763       56.65K/s    ETA 00:00

12:06:27 (32.04 KB/s) - `/usr/portage/distfiles/ppp-2.4.4.tar.gz' saved [688763/688763]