LAN [local-only] port-to-port testing

[The_Librarian]

Hi All

What app is there that I can use for testing LAN connectivity on different ports between two (or more) computers sitting on different LAN segments?

The network basically is like this (simplified)

[PC]-----network cable to main switch-----[main switch]--------network cable------[PC/Server]

Basically I want to run the application on the PC, then test connectivity through all ports to the target PC/server.

What happens is that we have the odd issue of some ports being blocked (for example the NTP protocol does NOT work on the one LAN segment but only on the other segment) and WSUS is giving issues galore yet Symantec Endpoint works fine.

My suspicion is that the port(s) in question are blocked on the main switch, but to verify that I need a software application that can do a test through a series of ports from one PC to the other.

TIA

Ook

 

[thehuman]

Axence.net nettools . Free registration

 

[HavocXphere]

I'd run a port scanner twice - once via the switch and once with a laptop connected directly to the target Pc via x-over

Obviously assumes you can take the server offline for a bit which is a big if

 

[gregmcc]

What switches do you have in place? I would very much doubt there would be specific ACL's on the switch to block ports (But then again I've seen worse)

To just check port connectivity use tcping. Like ping but for TCP ports

 

[The_Librarian]

I'd run a port scanner twice - once via the switch and once with a laptop connected directly to the target Pc via x-over

Obviously assumes you can take the server offline for a bit which is a big if

That's what I plan to do.

Offline server won't be an issue, we need to get to the bottom if this issue, we're losing out on penalties. So a downtime of 1 hour is preferable above losing money.

 

[The_Librarian]

What switches do you have in place? I would very much doubt there would be specific ACL's on the switch to block ports (But then again I've seen worse)

To just check port connectivity use tcping. Like ping but for TCP ports

HP ProCurve PoE 2530 jobbies.

I also doubt of any ACL's but then again I've had my share of a lot of network funnies during my career.

Ta for the TCPing tip

 

[letslogic.com]

Could be an ARP issue. If you can span a port on the the switch you can use wireshark.

 

[The_Librarian]

Axence.net nettools . Free registration

Thanks

 

[bekdik]

What happens if you test with all firewalls disabled?

 

[The_Librarian]

What happens if you test with all firewalls disabled?

Default ickdoze firewall rules allow for retrieval of ntp, wsus etc without blocking these

Besides we did disable firewalls to test, issue remains. So it narrows things down somewhat.