Subnetmask 255.0.0.0 and secondary IP

[BeNe]

Hello Togehter,

i added some more IP´s to ispCP under Settings -> IP Manage.
After that ispCP created a new Alias for eth0 like

Code:

eth0:5    Link encap:Ethernet  HWaddr 00:19:db:d5:83:5e
          inet addr:91.143.8x.xx  Bcast:91.255.255.255  Mask:255.0.0.0
          UP BROADCAST RUNNING MULTICAST  MTU:1500  Metric:1
          Interrupt:23 Base address:0xd800

So far so good, but why does we set here the Subnetmask 255.0.0.0 ?

The Problem is that i get everyday a new IP from my ISP at Home.
Today i have this one -> 91.22.2xx.xx and i can´t no more connect to my Server. It works perfect in the office and i asked all my friends -> no Problem.

I can´t Ping, and the Traceroute can´t also find a route to the Server.

I have an IP starting with 91.x.x.x and my new secondary IP for the Server start with 91.x.x.x and the Subnetmask is 255.0.0.0 -> CLASS A

I mean that this is the Problem and cant find a route to the Server.
Means that every Telekom Customer with an IP like 91.x.x.x cant connect to my Server ?!

Strange things happens here

Greez BeNe