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robclarke41

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cannot to connect to 2 switches on the network from particular IP

Hi All,

I have a very strange issue here - I cannot connect to 2 of the company LAN switches from 1 particluar IP address.

It doesn't matter which machine I use, all that I configure with this one address simply cannot connect to 2 certain LAN switches.

We have 5 identical 3COM superstack switches and have no security configured on any of them.

Has anyone experienced this before or have any idea what this could be?!
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woolmilkporc
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What's that address? What's the netmask?

wmp
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robclarke41

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Hi there,

The address is 194.129.15.211 mask = 255.255.255.0

All other addresses are able to connect to the switches i.e. 194.129.15.179 with mask 255.255.255.0 works fine

The switches are 194.129.15.246/247
Looks good.

Maybe it's a duplicate address? Please check everything connected to the two affected switches.

And the usual question: Any firewall or other device capable of blocking/filtering present?
have you tried power reset on the switches?
Well..

Its definitely not a duplicate address - tested and tested this.

I have checked and doubled checked that there is no filtering going on and can't find anything.  The 5 switches are connected to a firewall but the rules all make sense and there is certainly not one that references this particular IP address.

I'm totally stuck on this one!
I haven't tried resetting the switches - this is very hard to do as they are always in use.  Do you think it will work?
Did you check the logs (switches and firewall)?
I did, but the switch logs are very very basic and limited - nothing on the firewall.
When trying to connect check the ARP cache of the PC and also the ARP cache of the switch to see if they are resolving Layer 2 addresses or if there might be a static ARP entry or erroneous ARP entry in the switch for that particular IP.  Also try flushing the ARP cache on the switch.
Ok that sounds ike it might work - this is a heavily used LAN switch that many desktop users are connected to, is it safe to do this while they are working?
Is the firewall by any chance proxy arping on that address. Look in the switch arp table and check what MAC it thinks .211 is on.
Yeah completely safe.  When you flush the ARP cache it will just re-learn the addresses.  If the switch is your default gateway before your router or firewall (if it is routing as well) then there may be a few milliseconds before the default gateway address is resolved.  Shouldn't be noticeable at all though.
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jfrady

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