Resolving a mismatch against a hub port.

Answered Question
Aug 13th, 2007
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I have a VPN appliance external network interface connected to a 10/100Mbs hub.


I noticed performance issues and that the VPN appliance logs demonstrate transmission error in the interface connected to the hub.


By default, the interface is set to 'auto' detection.


I hardcoded the configuration in the network adapter interface in the VPN gateway to 100Mb/s, half-duplex, since hubs do not support full-duplex operation.


However, tranmission errors persist and performance is poor.


Question:

Is there any technical explanation on why even setting up this to 100Mbs, half-duplex did not match Ok with the hub?

Is the only solution for this replacing that hub with a switch?

Correct Answer by Tony.henry about 9 years 7 months ago

News2010a


The device your thinking of is a tap. Fluke have them, last time I looked.


Tony

Correct Answer by Edison Ortiz about 9 years 7 months ago

How about replacing that hub with a decent switch ? Not much we can suggest since you only have one side you can manage and you've done all possible combinations. The hub must go if you want better performance.

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balajitvk Mon, 08/13/2007 - 18:33
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Hi,


There are several possible reasons why the connection to the VPN appliance may be experiencing packet loss and performance issues. For interfaces, you want to verify that the interface speed and duplex settings are accurate for the both sides.


Pls. check whether your hub is supporting 100 or 10mbps per port. Whether you getting any specific error/warning msgs. for those ports on the VPN appliance side???


Rgs.

news2010a Mon, 08/13/2007 - 19:05
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Perhaps I was not clear in my explanation:


What I am saying is that I already set the network adapter configuration to 100Mb/s, half-duplex and that did not work. Errors persist. Setting as 'Auto', mismatch errors persist as well.


If I set it to 10Mb/s, half-duplex, I noticed that errors no longer are logged. However, at 10Mb/s, performance is poor and I believe that is now due to the low throughput.



Correct Answer
Edison Ortiz Mon, 08/13/2007 - 19:14
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How about replacing that hub with a decent switch ? Not much we can suggest since you only have one side you can manage and you've done all possible combinations. The hub must go if you want better performance.

news2010a Mon, 08/13/2007 - 20:58
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Guys, there is an *odd* situation in which some folks are arguing that the hub is adequate to let people monitor traffic reliably. Basically I have people arguing that if I put a 3750-48P there, ports configured as SPAN could drop packets on the mirrored port and that is not a reliable way to monitor traffic for important services there.


I heard in the past about a "in wire"(or something like that) device in which you could plug on the network which can address that scenario and let the monitoring folks connect their IDS/IPS there and let them examine the traffic without the need for a mirrored port.


Anyone ever used such solution and if so, please point me to more information on that.


Edison Ortiz Tue, 08/14/2007 - 05:45
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I haven't seen any reports of SPAN sessions dropping packets on the source port on any of the Cisco switches.


The device you selected as the hub replacement may be an overkill. If you aren't planning to run any intervlan routing on this segment, a 2960 would do a decent job for this task.

Pavel Bykov Tue, 08/14/2007 - 13:32
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The only case where SPAN session would drop packets would be when destination port becomes overloaded (e.g. mirroring fully loaded 100 mbps ports on one 100 mbps port).


Otherwise, SPAN works by sending a copy of everything to the destination port. There can be no drops. Only hardware problems can cause drops.

Correct Answer
Tony.henry Tue, 08/14/2007 - 15:15
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News2010a


The device your thinking of is a tap. Fluke have them, last time I looked.


Tony

news2010a Tue, 08/14/2007 - 18:01
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That's correct.

I talked with vendors today and found out that inline taps should address this situation. I will be ordering one for $1,200.

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