Switches, Hubs, and Modems
cancel
Showing results for 
Search instead for 
Did you mean: 

Monitor Port sniffing

Wayne Fussell
Occasional Advisor

Monitor Port sniffing

Greetings All,

I'm trying to see all the traffic going across a specific port. I've set the monitor port ON & selected a port to monitor. Plugged a laptop into the monitor port and I can see broadcast/multicast traffic from everywhere but can only see unicast traffic coming from the device on the monitored port not traffic going to that port ie only one side of the conversation. The switches in question are 4108GL's & 2524's with only the default VLAN.

Trying the same thing on a Dell switch shows both sides of a conversation.

I'm wondering if I've turned something on or off on the HP switches that is stopping me seeing all the traffic traversing that port.

Thanks in advance
In THIS house we obey the laws of thermodynamics - H. Simpson
3 REPLIES
Arimo Laine_2
Valued Contributor

Re: Monitor Port sniffing

Hi

"if I've turned something on or off on the HP switches"

You haven't. The switches indeed only show ingress traffic when you monitor. If you need to capture traffic on both directions, you need to plug a hub to the port which you want to monitor and connect the sniffer there.

Arimo
Wayne Fussell
Occasional Advisor

Re: Monitor Port sniffing

Thanks Arimo,

I'd previously done some looking around google on this issue and you've confirmed what I'd found.

What confused me was the port monitor on a Dell switch can see the conversation going both ways.

wayne
In THIS house we obey the laws of thermodynamics - H. Simpson
Ardon
Trusted Contributor

Re: Monitor Port sniffing

Hi,

Just one small note. The 2524 DOES monitor Ingress and Egress both at the same time. It's the 41XX having the limitatation of Ingress only.

Thanks, Ardon
ProCurve Networking Engineer