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PIX transparent mode and ARP

When PIX forwards an ARP Request in transparent mode, it inserts its own (!) mac address as source in the ethernet header. So it is not really transparent. E.G.:

Original ARP Request:

ETH Source: PC

ETH Destination: Router

ARP Sender HW: PC IP: PC

ARP Receiver HW: ? IP: Router

ARP Request after travelling through transparent PIX:

ETH Source: PIX (!!!)

ETH Destination: Router

ARP Sender HW: PC IP: PC

ARP Receiver HW: ? IP: Router

The problem is, that some end devices do not answer such an arp packet. And that is the trouble we run into ...

Any helping hand?

Thanks in advance

Edgar

2 REPLIES
New Member

Re: PIX transparent mode and ARP

I can't think of a reason why a server/PC would not respond to that particular frame, to all intents and purposes it doesn't care what the mac address is of the ETH Source.

I've been using PIX's in transparent mode for over a year now, and haven't experienced any problems like that. However I have routers on both inside and outside interfaces...

Andy.

New Member

Re: PIX transparent mode and ARP

Thanks for your reply. Normally the router should not care about the MAC source in the ethernet header. Nevertheless, it is not a normal behavior to have a different source than in the corresponding ARP request field.

I have changed pix os from 7.2 to 7.0(6) and now everything is fine: PIX do not change the source address any longer.

Edgar

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