DUP! replies to broadcast pings

DUP! replies to broadcast pings

Post by Mihails Nikitin » Fri, 14 Dec 2001 02:44:04



Hi,

I have a very simple question. Is it normal for Linux to receive duplicate
replies to broadcast ping?

ping 1.1.1.255
64 bytes from 1.1.1.1: icmp_seq=1 ttl=64 time=0 ms
64 bytes from 1.1.1.2: icmp_seq=1 ttl=255 time=0 ms (DUP!)
64 bytes from 1.1.1.3: icmp_seq=1 ttl=255 time=0 ms (DUP!)
64 bytes from 1.1.1.4: icmp_seq=1 ttl=255 time=0 ms (DUP!)

The only exception is single reply from originated host itself.

So, is it normal for ping implementation in Linux or I should check my network
configuration?
Thanks in advance!

BR,
Mihails

 
 
 

DUP! replies to broadcast pings

Post by Karl Heye » Fri, 14 Dec 2001 03:53:45



> Hi,

> I have a very simple question. Is it normal for Linux to receive duplicate
> replies to broadcast ping?

> ping 1.1.1.255
> 64 bytes from 1.1.1.1: icmp_seq=1 ttl=64 time=0 ms
> 64 bytes from 1.1.1.2: icmp_seq=1 ttl=255 time=0 ms (DUP!)
> 64 bytes from 1.1.1.3: icmp_seq=1 ttl=255 time=0 ms (DUP!)
> 64 bytes from 1.1.1.4: icmp_seq=1 ttl=255 time=0 ms (DUP!)

ping the broadcast address isn't normal, but does adding the -b
option make any difference.  I'm assumming 1.1.1.255 is your
broadcast address.

karl.

 
 
 

DUP! replies to broadcast pings

Post by Michael Muelle » Fri, 14 Dec 2001 07:36:31



> Hi,

> I have a very simple question. Is it normal for Linux to receive duplicate
> replies to broadcast ping?

Yes, as it is normal for any other operating system. It only does depend
on the system and settings of the host receiving the echo request.

Windows would receive the duplicate answers too but its ping utility
does ignore them as it ignores other conditions like change data in
returned answers.

Quote:> ping 1.1.1.255
> 64 bytes from 1.1.1.1: icmp_seq=1 ttl=64 time=0 ms
> 64 bytes from 1.1.1.2: icmp_seq=1 ttl=255 time=0 ms (DUP!)
> 64 bytes from 1.1.1.3: icmp_seq=1 ttl=255 time=0 ms (DUP!)
> 64 bytes from 1.1.1.4: icmp_seq=1 ttl=255 time=0 ms (DUP!)

> The only exception is single reply from originated host itself.

The only exception is the first answer received. By nature this is the
local machine responing if it does respond to echo request to this
address et all.

Quote:> So, is it normal for ping implementation in Linux or I should check my network
> configuration?

Again, yes it is normal. Ping does not decide for you wether the
displayed results are good or bad.

Michael

 
 
 

DUP! replies to broadcast pings

Post by Du » Fri, 14 Dec 2001 17:01:30



> Yes, as it is normal for any other operating system. It only does depend
> on the system and settings of the host receiving the echo request.

> Windows would receive the duplicate answers too but its ping utility
> does ignore them as it ignores other conditions like change data in
> returned answers.

Thank you, Michael! It looks like you said and everything depends on
implementation. E.g., Tru64 Unix behaves in the same way like Linux,
but HP-UX does not show (DUP!) marks.

Quote:> ping 1.1.1.255
> 64 bytes from 1.1.1.1: icmp_seq=1 ttl=64 time=0 ms
> 64 bytes from 1.1.1.2: icmp_seq=1 ttl=255 time=0 ms
> 64 bytes from 1.1.1.3: icmp_seq=1 ttl=255 time=0 ms
> 64 bytes from 1.1.1.4: icmp_seq=1 ttl=255 time=0 ms

Windows pretends as receiving non-duplicated packets from broadcast
address itself.

c:\>ping 1.1.8.255

Pinging 1.1.8.255 with 32 bytes of data:

Reply from 1.1.8.255: bytes=32 time<10ms TTL=255
Reply from 1.1.8.255: bytes=32 time<10ms TTL=255
Reply from 1.1.8.255: bytes=32 time<10ms TTL=255
Reply from 1.1.8.255: bytes=32 time<10ms TTL=255

Thanks again!

BR,
Mihails Nikitins

 
 
 

1. Why does broadcast PING report DUP!

Folks,

I'm using SuSE 7.1 - in case it makes a difference, I have two NIC cards for
two different networks, one of the networks has just been made redundant and
I have performed an 'ifconfig eth1 down'

My network consists of about 20 machines including a router to the outside
world - When I perform a ping 192.168.1.255 I get three of the servers
responding (192.168.1.1 / 2 / 3 / 15) - I don't object to the lack of
response from the other servers, but I do get a (DUP!) noted at the end of
each address, except from the originating server... forexample

64 bytes from 192.168.1.3: icmp_seq=0 ttl=255 time=0.312 ms
64 bytes from 192.168.1.2: icmp_seq=0 ttl=255 time=0.664 ms (DUP!)
64 bytes from 192.168.1.1: icmp_seq=0 ttl=255 time=0.865 ms (DUP!)
64 bytes from 192.168.1.15: icmp_seq=0 ttl=255 time=0.968 ms (DUP!)

I believe this is supposed to be a break somewhere on my network however
since all workstations are working fine, and all my network cards use RJ45
type connectors as opposed the BNC(?) type connections/daisy chains, where
could my problem be?

Can anybody give me more of an insight on what it could be and as to how I
could check?  It would be much appreciated...

Thanks,
Randell D.


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