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I have a PPPoE connection, that is MAC-protected by the ISP. I want to connect through a wired+wireless router. The router works perfectly for wireless users.

However, the wired connection fails to a Ubuntu 12.04 box - router indicates connection, but the PC - not.

I have set my router's MAC to match that of my PC. Could this be causing the wired connection problems?

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up vote 0 down vote accepted

Absolutely. IP addresses are allocated according to mac address by ARP, when a packet is sent, the router looks up the arp table to decide which physical address corresponds to which mac address. By having identical mac addresses, the packet is sent right back to the router.

Considering the situation, you either need to ask the ISP to change the mac address you're bound to, add a network card with a different mac address or fake your mac address with macchanger

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This is causing your problem. Every device needs a UNIQUE address. Both IP and MAC. I'm surprised your network is functioning at all with a duplicated gateway address. Remedy this immediately and configure Ubuntu as a DHCP client.

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