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Bizare Dell/Mac Behaviour

I am running a Guest Internet Network on 2950/3550 swithces and BBSM 5.2 will all latest patches.

2 guests using Dell computers (one XP and one w2k)and 1 Mac user are able to receive their IP address (DHCP) and also release and renew. They can ping any device in the management IP range (10.1.0.1 [GW] - 10.1.0.36) except the default gateway. They can ping any device in the client IP range (10.1.10.xx -10.1.15.254). They cannot pull up a connect screen.

I inserted a hub between the guest PC and the switch port, and and also connected my laptop (IBM Thinkpad running XP). My laptop can ping anything and go to the web. I ran Ethereal to capture data and tried to ping www.cnn.com on the guest's laptop. The guest machine did not use DNS, but instead tried to resolve using NBNS. Mine used DNS. I compared every setting page on the guest PC to the same page on my laptop and they are identical.

I cannot for the life of me figure this one out. I have almost 500 active rooms and only 3 guests have problems (different switches -2950- in different zones uplinking to different ports on the core -3550- switch). Why can't they even ping the gateway (AtNat port) but can ping everything else (internal) while I can? Again all settings on the PC's are automatic, nothing static.

Thanks.

8 REPLIES
VIP Purple

Re: Bizare Dell/Mac Behaviour

Hello Rob,

I remember having a similar problem a while ago, I got a big headache from searching and in the end I reboot the switch and miraculously all clients could connect. It seemed to have something to do with the ARP table that didn´t clear well.

Regards,

Georg

Anonymous
N/A

Re: Bizare Dell/Mac Behaviour

Thanks for the adivce, but I tried that (both a soft reload and a power off and back on with no luck). Guess I should have mentioned that....

Bronze

Re: Bizare Dell/Mac Behaviour

Rob,

It's possible that the BBSM has the DHCP-assigned IP address associated with another mac address. Do the following:

1. Determine the MAC address of the machine having the problem (by actually checking the machine or the DHCP lease).

2. From a command prompt on the BBSM, type the following:

atnatcmd local

where is = to the address assigned to the workstation by DHCP.

The MAC address the BBSM thinks is associated with that IP address will appear in parenthesis. If the MAC addresses don't match, deactivate the IP address in the BBSM and clear the mapping with the command 'atnatcmd clearmap .

~Zach

Anonymous
N/A

Re: Bizare Dell/Mac Behaviour

OK. I went to try that this morning and one of the guests has left, but the other one is now able to connect even though I have not yet done anything.

I don't know what he did. Is it possible it could have been IP spoofing by another guest?

Bronze

Re: Bizare Dell/Mac Behaviour

It could have been spoofing. It could have also been the result of a feature introduced in SP2, whereby the BBSM blocks traffic from IP addresses that are associated with a different mac address in its database.

Questions:

1. Are you using switch port state or inactivity timeout to disconnect your BBSM users?

2. Are there any downstream devices (hubs, switches, etc.) connected between the switches configured in the BBSM and the clients?

Anonymous
N/A

Re: Bizare Dell/Mac Behaviour

In the guest rooms, I'm using switch port state as there are no non-manageable switches between the guest room and the server. The only devices are an uplink to no more than one 2950 (dependant on which floor -- these guest rooms in particular uplinked to a 2950) and then an uplink to a 3550 as a core switch and then out to the AtNat port. In the meeting rooms, they all uplink to only 2 ports on a 2950 so there are multiple l2 only devices and I believe that this zone uses packet inactivity. I would have to go into the system today to check to be sure, but I'm not at work today (it's my Sunday), so I will re-verify tomorrow.

Thanks.

Anonymous
N/A

Re: Bizare Dell/Mac Behaviour

Further to your points above, I am using switch port state in the affected areas for disconnection.

With regards to point 2, the guest to who I originally referred, was able to connect on a different LAN segment where there IS a dumb switch between him and the Cisco switch port. However, directly connected to the switch was a no-go.

Thanks.

Anonymous
N/A

Re: Bizare Dell/Mac Behaviour

I believe I found the solution. One segment of the LAN (meeting rooms) uses access codes to connect. If the guest fails to disconnect using the IPORT toolbar disconnect button (just shuts down and walks away), their session doesn't deactivate properly. Their IP address is held alive. Another guest later on (after original DHCP lease expires) can get the same IP address from the w2k server.

Consequently, the server senses this as an IP conflict. To resolve the issue, manually deactivate the client session which has the same IP address (but different MAC address) and ask the guest to reboot, or give the other guest a fictiional static IP address and let BBSM draw from it's foreign pool

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