Networking → Hub for network sniffing - disadvantes

I was thinking of placing a hub (Netgear DS104) between my radio and my router so as to sniff the traffic to/from my lan. This seemed like a good idea until I realized that it may slow down my connection if I leave it in. Of course I could plug/unplug or switch it, but I was hoping to just leave it in and only switch a computer in and out of it. In other words, I'd like to make this both free and easy.

Will I be slowing down traffic by doing this? The wireless normally works at 1-2.5mbps and only very rarely peaks up to 3mbps, so the 10/100 connection issue shouldn't be a problem. However, I'm not clear on the duplex issues. The Wireshark and other sites seem unclear on this, and it sounds like perhaps the only good way to sniff all traffic is with a tap and two network cards, which I was hoping to avoid.

tldr: Will leaving a hub permanently connected between a wireless radio and router impair the connection?

The limitation of hubs is that all communication is half-duplex and only one device is able to transmit at a time.

Wireless is inherently half-duplex and if you are only using the hub to sniff traffic nothing else will be consuming bandwidth.

/tom

Thanks tom. I assumed that wireless had to be half duplex but didn't know if the radio used two channels, or how it was set up. Although it is physically mine, it is part of the configuration with the ISP's tower and thus out of my control.

It sounds like in my case this is a perfect solution - especially considering that I already have that old hub which I never thought would find a use.

You can always prove it to yourself run a speed test with and without the hub.

/tom

If you still wanted to monitor the line at full speed / duplex and without risk of collisions, you could pick up a switch that supports port mirroring. A relatively cheap example would be the 5 port Netgear GS105e

Thanks GM85. I didn't realize that a port mirroring switch was available at such an affordable price. I definitely remember that when it comes time for some upgrades.

Well, I finally got a suitable power supply wired up and mounted the hub on the wall.

The first thing I did was do some speed tests as you suggested. I can't see any difference with the unit in or out. Average is about 2.11mbps down and 2.58mbps up. That's about what I usually get on speed tests. I guess that shows that I can leave it connected.

I haven't tried any Wireshark yet, but am looking forward to playing with this new setup.

Thanks for the helpful comments.

2nd the comments about hub being halfduplex and getting a switch that does port SPAN'ing.

There's something called a network tap that I've heard of that supposedly is truly non-linerate limiting, but if you're
only talking 3Mbps peak traffic I wouldn't bother with this option.

Regards

The network tap looks easy to construct if one has some radio-electronics skills, but I really wanted to make this as quick and easy as possible for the time being. I think you're right though, that's the best way to go.

As for half duplex; if both the hub and the source signal are half duplex, then what is lost? I note that I'm not seeing a difference in speed with the hub in or out.

For your speeds and needs the HUB is perfect fit. ...the horse is dead