ports and protocol for

[PamelaJThrasher]

I need to put in a firewall request to allow one of my servers (phcb1cne) to remsh to another server (phcb1cnb) and start a package (cmmodpkg -e pkg_name).

I do not believe the phcb1cnb will need to respond to the phcb1cne.

What port(s) do I need to open on which server(s) to make this work? Also what protocol is remsh? UPD? TCP? Both? Something else?

Thanks in advance.

[Ganesan R · Accepted solution]

Hi,

By default all the unsecure ports will be blocked at firewall. If you need only remsh port to be opened on firewall, ask them to open 514.

remsh uses the port number 514. You can also check in /etc/services file to find if the port is enabled on servers.

#grep 514 /etc/services

[PamelaJThrasher]

Here is what I see from grep 514 /etc/services

shell 514/tcp cmd # remote command, no passwd use

looks like I am all set.

Thank you!

[Ganesan R]

Hi Again,

Yes. From server side remsh port is open. And it should be opened at firewall as well if there is a firewall between the servers.

To confirm if the port is opened on all the places, use this command,

#telnet 514

Trying...
Connected to
Escape character is '^]'.
Connection closed by foreign host.

If you get the message like above you are through.

[PamelaJThrasher]

Will do. Thanks again.

[Tim Nelson]

I see you got your answer and only wished to add one comment..

In this day and age of cybercrime using unencrypted protocals should be detered.

using ssh (port 20) would help thwart the criminals.. the more fences put up the more likely they would move on to somewhere else.

[PamelaJThrasher]

Tim-
Thanks for the words of advice. I will encourage my customer to re-architect their failover solution to not rely on remsh.

[PamelaJThrasher]

.

[Steven Schweda]

> using ssh (port 20) [...]

Would tend to confuse people, because port
20 is normally used for FTP. Port 22 is more
common for SSH (although security fanatics
often suggest using some other port for it,
to evade common attacks on port 22).

http://www.iana.org/assignments/port-numbers

Note also that port 514 (shell) may be used
for rsh/remsh with a command, while port 513
(login) may be used for rsh/remsh for an
interactive session (without a command).
That is, for example,
remsh host
and
remsh host 'sleep 30'
don't use the same port.

"netstat -an" can be helpful when exploring
in this region.