Here is one that has me stumped.
I have a Realtek network card:
01:00.0 Ethernet controller: Realtek Semiconductor Co., Ltd. RTL8111/8168B PCI Express Gigabit Ethernet controller (rev 03)
I have the default gateway set correctly and no outbound filtering on the border firewall (Netgear FVS338).
I can access anything on the local network directly.
I can access external sites through a proxy on the network.
I can't access external sites directly.
I have a laptop next to me that works fine.
I've rebooted the firewall, but it doesn't help.