What does "(DUP!)" mean?

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Level 1

6 points

What does "(DUP!)" mean?

Hi, I have a WDS network.
The IP address on my airport extreme is 10.0.1.0
The IP address on my airport express is 10.0.1.197
The IP address on my imac is 10.0.1.199.
There are several over devices on the network but they are mainly wired clients.

When I type ping 10.0.1.0, I receive this.

64 bytes from 10.0.1.1: icmp_seq=2 ttl=255 time=4.314 ms
64 bytes from 10.0.1.198: icmp_seq=2 ttl=64 time=4.557 ms (DUP!)

Just wondering:
A)what (DUP!) is
B)why it is giving me 10.0.1.198 as well, when I am not pinging it.

24" Imac, 2.16Ghz, 2GB Ram, 7600GT, Mac OS X (10.4.10)

Posted on Feb 24, 2008 11:36 AM

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Answer 1

Camelot

Level 9

59,807 points

Feb 24, 2008 12:03 PM in response to Dave Jerome

DUP! means that it is a duplicate packet - for example, if you send out one ping but got two replies, the second one will be a DUP!

From looking at your post, the critical information is the subnet mask in use on your network.

If your subnet mask is 255.255.255.0 then 10.0.1.0 is not a valid host address and you should not use that for your base station.
You can't use the first (.0) or last (.255) address in a 255.255.255.0 subnet.

That's because the first address (.0) is known as the network address and that last address is the broadcast address. Most devices in the network should respond if you ping the broadcast address. Some (but not all) devices will also respond if you ping the network address. It appears from your post that whatever device is at 10.0.1.198 is responding to the network address.

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