灌ubuntu server中mirror設定 - Linux

[問題簡敘]
在實體機上裝ubuntu server
之前都是在vmware裡裝ubuntu server
沒有在實體機裝ubuntu server 系統的經驗
第一次裝在mirror的選擇上就卡關

[安裝步驟跟訊息]

[configure the network]的部份

namde server addresses:
這裡我輸入我們實驗室的ip:140.128.101.141.143


輸入hostname

[choose a mirror of the ubuntu archive](這裡出問題↓↓↓)
第一步-------------------------------------------------------------
the goal is to find a mirror of the ubuntu archive that is close to you on
the network --
be aware that nearby conutries,or evenyour own ,
may not be the best choice,
ubuntu archive mirror conutry:
我選taiwan
第二步---------------------------------------------------------------
please select an uubntu archive mirror.
you should use a mirror in your country or region
if you do not know which mirror has the bes internet connection to you.
usually,<your contry code>.archive .ubuntu .com is a good choice.
ubuntu archive mirror:

只能選tw.archive.ubuntu.com
第三步---------------------------------------------------------------
if you need to use a HTTP proxy to access the outside world ,
enter the proxy information here.otherwise, leave this blank.
the proxy information should be given in the standard form of
"http://[[user][:pass@]host[:port]/".
HTTP proxy information (blank for none):
我不知道要輸入什麼??
就按下continue
就出現錯誤訊息



[錯誤訊息]------------------------------------------------------------
an error has been detected while trying to use the specified ubuntu archive
mirror.
possible reasons for the error are:
incorrect mirror specified;mirror is not available
(possibly due to an unreliable network connection);
mirror is broken
(for example because an invalid release file was found)
additional details may be available in /var/log/syslog or on virtual
console4.
please check the specified mirror or try a different one

不知該如何處理??


--