Isolate PPPoE IP address from LAN port

Unanswered Question
Oct 13th, 2007
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Hi,

I have a 2800 router, with one LAN port(G0/1) set to a local IP address (say 10.10.10.10) and is connected to a LAN switch, and another LAN port(G0/0) is used for PPPoE DSL modem (fixed IP, say 222.222.222.111) connection. The problem is that if I connect a PC, whose IP address is in the same subnet of the PPPoE's, say 222.222.222.112, to the same LAN switch with G0/1, while I ping 222.222.222.111 from PC, G0/1 responses the ARP request that 222.222.222.111 is him. Is there any way to prevent G0/1 from recognizing himself as 222.222.222.111?


Thanks much.


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aghaznavi Thu, 10/18/2007 - 14:20
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this is proxy ARP functionality . if the router receives an ARP request for a host that is not on the same interface as the ARP request sender, and if the router has all of its routes to that host through other interfaces, then it generates a proxy ARP reply packet giving its own local data-link address. The host that sent the ARP request then sends its packets to the router, which forwards them to the intended host. Proxy ARP is enabled by default.


If you want disabel this functionality follows the following commands and set the default gateway in your PC.

Router# configure terminal

Enter configuration commands, one per line. End with CNTL/Z.

Router(config)# interface giga0/1

Router(config-if)# no ip proxy-arp

Router(config-if)# ^Z

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