Re: [SLUG] switch sought

From: Chris Mathey (slug@mathey.org)
Date: Mon Sep 01 2008 - 08:30:10 EDT


Eben King wrote:
> On Sun, 31 Aug 2008, Chris Mathey wrote:
>
>> Eben King wrote:
>>> (Short) Can anyone recommend an 8-position switch? I probably
>>> should spring for 100 MHz signaling rate this time.
>>>
>>> (Long) Not counting Verizon's in-home router, I have two 4s; the
>>> first is 10 MHz (no NAT; is it therefore a hub?), and the second is
>>> the same as Verizon's and I intend to move it when DD-WRT is
>>> released for it. (Yes, that's right folks, from things on the last
>>> one, there's three _things_ before the packet leaves the house.)
>>> Anyhow, of the seven ports I have available under my desk, I've used
>>> six. So I'd like to replace switch/hub #1. Suggestions?
>
>> Hubs are deprecated. You probably won't find them anymore (ebay of
>> course). The reason being is that they are merely simple repeaters. A
>> frame seen on one port is repeated to every port on the device. They
>> also can only utilize half duplex operation
>
> I'm not looking for one; I'm just thinking what I have _is_ one.
See if it's capable of 100 full duplex operation. A Hub cannot do 100
full duplex
>
>> A switch learns all the MAC address that are connected to it. If a
>> frame enters a switch with a destination MAC address located on that
>> switch, it will be sent to that port. All other ports on the device
>> won't see that frame.
>
> How does one do sniffing in such a situation? Will VM such as VMware
> still work?
Say you do a tcpdump. It only will pick up unicast and packets destined
to any MAC address bound to that NIC and of course broadcasts/multicasts.
More expensive managed switches will often have a port mirroring
function. i.e. mirror all ports to port x.
Most switches i've seen can handle 8192 MAC address. VMware is no problem.
>
>> Personally I like Netgear prosafe products. Their consumer grade
>> stuff has been very reliable and well built IMO.
>> Also... spend a couple more bucks and go gigabit.
>> http://www.newegg.com/Product/Product.aspx?Item=N82E16833122140 (8
>> port gigabit netgear $49)
>
> Given the quality of the run through the attic, I don't think I'd get
> a gigabit connection. Also, the pipe out to the net is much slower,
> estimated to be below 10 Mbps given the fastest download I've seen
> (~900 KB/s).
>

One more thing. Don't hard code a network card 100 full duplex on
unmanaged switches. auto negotiation requires /both/ the switchport and
network card set to auto to operate reliably.
Newer hardware handles this better but when one side is set for 100 full
it will often result in a duplex mismatch.

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