Network Slowness

I'm not sure what exactly is going on, but let me explain a few things
about the network. We have some Linux machines on campus that are
accessed via a V-Lan. When doing NFS over the v-lan, the directories
mount, but when doing an "ls" on the directory, things lock up. I can
do an ls on a particular file just fine. A work around was the limit
the read and write buffers to 1024. I'm not sure what the reason for
this is.

Another problem we are having is that with logining in via RSH, the
server connects instantly, but till a login prompt is gotten it takes
a long time (maybe 30 seconds or so). Telnet or SSH goes instantly. I
checked the resolv.conf file on both the client and server and those
nameservers work.

There is a firewall running IPTables between the 2 networks. Over the
V-lan they are 2 different IP ranges.

If anyone has any insight as to what is going on, this would be
appreciated.

Thank you,

Lawrence