What could be the cause when the first half of the C-class IP work, the other half not work? [closed]

Question

For example, the IP xxx.xxx.xxx.1-127 works, but xxx.xxx.xxx.128-251 are not working. They are working before. Thanks.

Define "work". Are nodes not able to access information out of the subnet, or the converse; nodes outside of the subnet can't access those nodes? Or something else?
There's a website bind with each IP, I can see the website with IP xxx.xxx.xxx.1-127, but not with xxx.xxx.xxx.128-251. Those IPs are in the interface. Thanks.
Can you ping the other addresses? Agreed with KCotreau; the most straightforward cause for this would be an incorrect subnet mask. One way this could happen is if the bad mask is part of the route directing traffic towards you in your upstream device (firewall, router, etc.).
I can't ping them. I will get the network admin to fix it. They may changed something that I don't know. Thank you.
For goodness sake, there's no such thing as a Class-C network. There hasn't been for years. And years. And years: meta.serverfault.com/questions/514/… and serverfault.com/questions/12854/cidr-for-dummies

KCotreau · Accepted Answer · 2011-05-24 01:01:58Z

up vote 5 down vote accepted

The first thing that comes to mind is an incorrect subnet mask somewhere, but you really need to give more information. What exactly are you doing?

answered May 24 '11 at 1:01

KCotreau
2,4011623

closed as not a real question by Jim B, John Gardeniers, Ward, Scott Pack, Bart De Vos May 26 '11 at 12:24