Our DBA's have installed Sybase on to redhat 5.8 and would like to connect to it using ISQL/w.
I have disabled the firewall since it is only an internal server but they still cannot connect.
I also cannot telnet to this port from a PC.

I get the foolowing shown:
/]# nmap -sS -O 127.0.0.1

Starting Nmap 4.11 ( http://www.insecure.org/nmap/ ) at 2013-01-29 16:00 GMT
Interesting ports on localhost.localdomain (127.0.0.1):
Not shown: 1672 closed ports
PORT STATE SERVICE
22/tcp open ssh
23/tcp open telnet
25/tcp open smtp
111/tcp open rpcbind
631/tcp open ipp
971/tcp open unknown
5800/tcp open vnc-http
5801/tcp open vnc-http-1


Is there anything else I can do?

Check http://infocenter.sybase.com/help/to...018594631.html for an extensive list of ports Sybase seems to use.

an nmap in "default" mode (nmap -sS -O 127.0.0.1) may not be sufficient.

Which port is referenced when you said "I also cannot telnet to this port from a PC."

telnet localhost <port> from the sybase host should work.

I'd try
or on the sybase host and look for the sybase port (this assumes the service/daemon is started...) then
with an additional
The goal here is to find a range of IPs and nmap those. Or just use "the port" you mentioned and skip the whole nmap'ing a range, but use nmap -sS -O 127.0.0.1 -p <port_you_mentioned>

If the sybase port is running and they still cannot connect, they should try
or to verify "They" can 'see' the server from client PCs.

Are they behind a corporate firewall, or other another device that may be "in the way"? (Not a firewall as you mentioned)

Please let us know...

127.0.0.1 is (as it says) the localhost aka loopback addr.
You need to look at the network addr (eg as used by eth0).