"problem" with portmap

["Dietrich Beck" <Dietrich.Beck@fys.kuleuven.ac.be>]

Hi,

we have small PC cluster running Debian 2.1. Since a few days to of those bother me with the following message:
"my_host portmap[6050]: connect from 134.58.X.Y to callit(ypserv): request from unauthorized host". In principle that is o.k., because 134.58.X.Y should have no access to our cluster. It is just, that this message appears once per minute and only at two out of seven boxes.

I checked with "tcpdump" and it seems, that 134.58.X.Y sends a request to the address 134.58.255.255, which is then picked up by my_host (my_host has a different IP number, of course). Does anybody has an idea why only 2 out of 7 boxes have that behaviour? Since it is the same software it must be some setting, maybe in /etc. But where? How I can prevent the "portmap" from picking up the request? It simply annoys me.

Greetings,

        Dietrich

P.S. 134.58.X.X is a machine of a neighboring institute. It is not a hacker attack.