[root@itcast01 local]# yum install lrzsz
Loaded plugins: fastestmirror, refresh-packagekit, security
Setting up Install Process
Loading mirror speeds from cached hostfile
YumRepo Error: All mirror URLs are not using ftp, http[s] or file.
Eg. Invalid release/repo/arch combination/
removing mirrorlist with no valid mirrors: /var/cache/yum/i386/6/base/mirrorlist.txt
Error: Cannot find a valid baseurl for repo: base
[root@itcast01 local]# ping baidu.com
PING baidu.com (39.156.69.79) 56(84) bytes of data.
64 bytes from 39.156.69.79: icmp_seq=1 ttl=128 time=29.2 ms
64 bytes from 39.156.69.79: icmp_seq=2 ttl=128 time=28.1 ms
^C
--- baidu.com ping statistics ---
2 packets transmitted, 2 received, 0% packet loss, time 1774ms
rtt min/avg/max/mdev = 28.135/28.692/29.249/0.557 ms
题主的网络连接看起来是正常的，试试换下yum的源。或者ping下yum源的网址，看通不通。
可以参考下下面两个文章：
https://www.tecmint.com/fix-cannot-find-a-valid-baseurl-for-repo/
https://blog.csdn.net/qq_41684957/article/details/83345154
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