funny ip problem

[Howard W Wortley]

We have in one city a co-located server with a class C set of addresses.
This works fine except that from one cable provider every fourth address
cannot be reached. From any other provider there is no problem. The cable
operator says he has no fault. Any ideas?

eg.	x.x.x.142	no good
	x.x.x.143	ok
	x.x.x.144	ok
	x.x.x.145	ok
	x.x.x.146	no good ... and so on

I don't think it is a DNS problem as using tracert the ip adress get
resolved to the host name ok ... but the connection cannot be reached. As
the DNS is on the same server as the unreachable ip connection I am
mystified. As I said it only happens to hosts connecting through this
particular cable company's cable which hands out DHCP addresses. As it is
every fourth address I imagine it is some kind of routing problem.

TIA Howard