Hi, all,
I asked before why my linksys workgroup 5-port switch worked like
a hub
under heavy traffic (10mb/s) into one socket of the switch. The conclusion
is that the switch has some problem.
In fact, for the first 5 minutes, it
works like a switch and then it works like a hub. The switching table is
messed up by the intense traffic, we believe. Other cheaper switches
(netgear fast esthernet switch FS108 ) have the same problem. We use a
CentreCom FS708, and then the problem is solved. Of course other expensive
and professional switches should be ok too, we think.
Just some information.
Xinwen Fu
---------- Forwarded message ----------
Date: Thu, 8 May 2003 22:49:01 -0500 (CDT)
From: Xinwen Fu <[email protected]>
To: Linux Kernel Mailing List <[email protected]>
Subject: linksys workgroup switch works like a hub
It is really weird!
Host_10.1--->10.254_router_1.254--->Linksys 5-port workgroup switch-->Host1.1
| |
| |
v v
Host_1.10 Host_1.5
Host_10.1 sends 1000 packets/s (pps) to Host_1.10. Host_1.10 receives the
packets. But Host_1.5 receives the packets too, while Host_1.1 does not
(by tcpdump -i any).
What is the possible reason?
Thanks!
Xinwen Fu
Xinwen Fu wrote:
> The switching table is
> messed up by the intense traffic, we believe. Other cheaper switches
> (netgear fast esthernet switch FS108 ) have the same problem.
What do you mean by "intense traffic?" Many switches will get
confused if you fill their tables with a large number of different
addresses. Is someone maybe spoofing MAC addresses on your net?
Or is the switch plugged into a larger switched network where it will
see many different MAC addresses on the uplink port?
Also, almost every switch will flood all ports with traffic for
machines that have disappeared recently (disconnected or changed
their MAC addresses.) High-end switches have settings to control
this problem but it's impossible to avoid some leakage.
Never count on an ethernet switch to provide privacy for traffic
on a single VLAN.
Chuck,
>
> > The switching table is
> > messed up by the intense traffic, we believe. Other cheaper switches
> > (netgear fast esthernet switch FS108 ) have the same problem.
>
> What do you mean by "intense traffic?" Many switches will get
> confused if you fill their tables with a large number of different
> addresses. Is someone maybe spoofing MAC addresses on your net?
> Or is the switch plugged into a larger switched network where it will
> see many different MAC addresses on the uplink port?
By Intense traffic I mean that the traffic on one path through the
switch is a little more than 10mb/s.
My testing enviroment is an isolated lab environment. I only use
4 ports and the uplink port is not used. Each of the 4 ports is
connected to one ethernet card. That is why I concluded that the
10mb/s traffic is intense since for the first 5 minutes the switch is a
switch and then becomes a hub.
As I said, I used a little expensive swicth (also auto-sensing
dumb one) and solved the problem. That is why I concluded a very cheap
swicth (<$100) may be not good in some scenarios. Of course for household
use,
it is definitely a good choice.
Xinwen Fu
P.S. I only intend to provide some information and all my testing is for
a rigid academic objective.
Followup to: <[email protected]>
By author: Xinwen Fu <[email protected]>
In newsgroup: linux.dev.kernel
>
> Hi, all,
> I asked before why my linksys workgroup 5-port switch worked like
> a hub
> under heavy traffic (10mb/s) into one socket of the switch. The conclusion
> is that the switch has some problem.
>
> In fact, for the first 5 minutes, it
> works like a switch and then it works like a hub. The switching table is
> messed up by the intense traffic, we believe. Other cheaper switches
> (netgear fast esthernet switch FS108 ) have the same problem. We use a
> CentreCom FS708, and then the problem is solved. Of course other expensive
> and professional switches should be ok too, we think.
>
Do you have lots of machines on your network? All switches has a
limit on the number of MACs they can remember.
-hpa
--
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