Odd behavior in a DMZ

Has anyone ever experienced this kind of behavior on a network segment that is actually a DMZ off of a PIX.

Pinging between the 3 devices on this same segment is erratic. I thought it had to do with possibly mis configuring the Netmask but that all seems correct.

This DMZ off of a PIX515E firewall has 3 devices on it now. Two Linux and now a laptop for testing.

linux1 IP= MAC= Mac1 Linux2 IP= MAC=Mac2 Gateway MAC=GatewayMac WinXP laptop MAC=LaptopMac

We added linux2 which needs to communicate with Linux1 but the connectivity is flaky. If we ping from linux2 to linux1 usually the ping hangs there. (We captured a broadcast packet and it seems that the packet would have the IP address of LInux1 but the MAC of the Gateway)

While the above was ping was running if you were to initiate a ping from linux1 all of the sudden the linux2 ping begins to get responses and work.

Basically inside this DMZ ping connectivity seems pretty strange and Odd between the 3 devices there. It does not seem to be any one device causing it so I am thinking it must somehow be related to the configuration of the DMZ? How could that be especially if the problem clears up occasionally. One device is a spam device so we called the vendor to check if there were some type of security setting preventing it's accepting pings but that is not the case. Plus even the pings this devices initiates are sometimes flaky.

Cleared out ARP tables several times but problem seems to persist.

Does anyone have any thoughts as to why broadcasts might not work reliably on this network? Or suggestions on where to look?

I hope I provided enough information. Thanks, Secsam

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Did you set the arp proxy?

cheers, RL

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This is not my strong suit --so forgive me if I sound like a total noob.

ARP Proxy is set-- But does that really have a bearing since the devices are on the same broadcast network and trying to talk with each other? I though ARP-Proxy relates more to communications with devices on other network segments.

Thanks again....

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Figured out the problem thanks to someone reading the message. Apparently we need to turn off "arp proxy" because it impacts communication between devices, even on the same network.

If you are interested see this article:

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Thanks for the assistance.

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