Tagged and Untagged VLAN

Question

We are having a Dell power connect 2748 switch. We have been facing an unusual problem. This switch is uplinked to a Cisco L3 switch which inturn caters to the WAN Connectivity. We have multiple VLANs on the Dell and have created a trunk between the dell and the cisco switch and have tagged all the VLANs over the trunk port. We also tagged the access port for specific VLANs. What we observed that for an XP system connected to a Tagged access port, the system was able to receive an IP via DHCP whereas on the same port if we connected a Win7 PC it failed to get an IP. To get around this we figured out to leave the access port as untagged for the specific VLAN, post which Windows 7 PC accuired IPs. But later on we found huge lags in accessing any app over the XP systems which were connected to a Tagged access port. Again we switched the access port to an untagged VLAN and everything was working smoothly. Could anybody explain the logic of impact of an untagged / tagged frame on the overall network performance. Thanks,

ssr9583 · Answer

Hi Daniel,

Thanks for the response. I understand what you have said, but still fail to understand the reason for slowness in the traffic for a tagged port. I believe considering they are VLAN unaware devices nothing should have worked in case of it being connected to a tagged port.

Please correct me if my understanding is wrong here. I am trying to figure out the lag that was being caused because of the tagging.

Thanks,

Srinivas

Networking General

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