Question about multicast and ping

magodiafano · 11-23-2010, 10:12 AM

Hi I have a question.
In pinged the default route for multicast traffic 224.0.0.0 .

When i see the output I have this result:

[guest@shakti guest]$ ping 224.0.0.1
PING 224.0.0.1 (224.0.0.1) 56(84) bytes of data.
64 bytes from 128.238.66.100: icmp_seq=1 ttl=64 time=0.041 ms
64 bytes from 128.238.66.104: icmp_seq=1 ttl=64 time=0.399 ms (DUP!)
64 bytes from 128.238.66.103: icmp_seq=1 ttl=64 time=0.524 ms (DUP!)
64 bytes from 128.238.66.102: icmp_seq=1 ttl=64 time=0.651 ms (DUP!)
64 bytes from 128.238.66.106: icmp_seq=1 ttl=64 time=0.841 ms (DUP!)
64 bytes from 128.238.66.101: icmp_seq=1 ttl=64 time=0.942 ms (DUP!)
64 bytes from 128.238.66.107: icmp_seq=1 ttl=64 time=1.12 ms (DUP!)
64 bytes from 128.238.66.105: icmp_seq=1 ttl=64 time=1.22 ms (DUP!)

My address is 128.238.66.100. I would like to know what are that DUPs! ?!
And from this output could I say that all the hosts(such as 128.238.66.101) have replied when the broadcast address was pinged?

jefro · 11-23-2010, 04:43 PM

My guess is you pinged a bunch of ip's from a single number. Since it was a broadcast number everyone returned a reply. Since the original request was a number different than the reply it says dup for duplicate.

goldenbarb · 11-24-2010, 03:25 AM

man ping

Code:

ping will report duplicate  and  damaged  packets.   Duplicate  packets
should  never  occur, and seem to be caused by inappropriate link-level
retransmissions.  Duplicates may  occur  in  many  situations  and  are
rarely  (if  ever)  a good sign, although the presence of low levels of
duplicates may not always be cause for alarm.