How to check open ports on a destination server FROM ESX

[VirtualKenneth]

Hi,

I'm wondering this for a long time now but I never had time to dig into it.

From Windows it's easy to check if a port on a destination server is open by just telnetting to it with the corresponding port number. How do I do this FROM an ESX host?

Is there something like telnet on there that i'm unaware of? (nmap isn't installed on ESX by default)

Thanks,

Kenneth

[ShanVMLand]

Telnet is not installed by default. Not Recommended. If you need you can mount installable CD and in RPMS folder, you can find the telnet RPM.

Shan

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[VirtualKenneth]

But isn't there some ESX (Redhat) default command that is installed defaulty for this purpose?

[ShanVMLand]

I am seeing the following commands possible to see "LISTEN". I have no luck with finding any equal commands like "telnet/nmap"

1. netstat -a | egrep 'Proto|LISTEN'

2. lsof -i -n | egrep 'COMMAND|LISTEN'

Shan

[bulletprooffool]

I spent a fair bit of time looking into this and there is no easy way to test whether ports are open between the ESXi Host and another machine (at least from a VM point of view)#

Are you trying to test connectivity to the management console, or a VM - as if it is a VM you can simply use the resident OS tools for that? Telnet etc?

[VirtualKenneth]

I'm seeing this from a ESX point of view, from a VM point of view it's

quite easy.

bulletprooffool said the following on 28-5-2009 13:54:

Kenneth van Ditmarsch,

A new message was posted in the thread "How to check open ports on a destination server FROM ESX":

http://communities.vmware.com/message/1264936#1264936

Author : bulletprooffool

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Message:

[dmartushev]

The easiest way I found to do this using the default tools available on an ESX Host is just to use the SSH client utility bundled in.

For instance, run the command:

ssh <server-name> -p <port #>

and if you get an error to the effect of: ssh: connect to host testserver.corp.lan port 27010: Connection refused then the firewall is likely denying access.

But, if the command doesn't error and just waits on the screen then a TCP connection has been establish thereby showing that some type of access has been given through the firewall. Sort of like using Telnet on a WinTel box.