I have a remote user that has Verizon DSL and connects through his Netgear wireless router to his personal PC via Ethernet and to our company laptop via wireless. The problem is that only one device works at a time. If he disconnects his personal PC the laptop works, and if the laptop is off, the PC works. I have replaced the Netgear router and the same problem persists. Any suggestions?
Since you have tried more than one wireless router and encountered exactly the same issue, you are probably looking at a network layer problem with routing, addressing, or packet size.
Many DSL problems actually stem from the provider's use of PPPoE and the need to tune maximum transmission unit (MTU) size. I haven't encountered your problem before, but suggest searching the Verizon Online DSL FAQ and related user forums for anyone who encountered this same scenario.
If you haven't done so already, you should also verify that the laptop and PC can communicate with each other locally on the LAN, without using the DSL uplink to the Internet, to eliminate any local sources of interference (for example, duplicate/conflicting private IP addresses).
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