question about network address and broadcast address
 

Hi all,

I just feel very confused about some basic network concept.
Today I found I can *ping* a network address, like the following
lines:
-------------------------------------------------------------------
[root@root]# ping 10.0.42.0
PING 10.0.42.0 (10.0.42.0) from 172.16.12.12 : 56(84) bytes of data.
64 bytes from 10.0.42.0: icmp_seq=0 ttl=126 time=3.443 msec
64 bytes from 10.0.42.0: icmp_seq=1 ttl=126 time=2.085 msec
--------------------------------------------------------------------
I know when I *ping* a host, actually I send a packet to that host and
then the packet returns back to my PC. But now I *ping* a network
address. Where does this packet go to? Does it mean that I am sending
the packets to every host in this network? If so, what will happen
when I *ping* a broadcast address?
---------------------------------------------------------------------
[root@root]# ping 10.0.47.255 -b
PING 10.0.47.255 (10.0.47.255) from 172.16.12.12 : 56(84) bytes of
data.
64 bytes from 172.17.4.33: icmp_seq=0 ttl=254 time=1.907 msec
64 bytes from 172.17.4.33: icmp_seq=1 ttl=254 time=1.246 msec
-----------------------------------------------------------------------
Please help me to explain the principle.
Any suggestion will be appreciated.

fish

Depending on your router and the devices on your network, you may get a response from every device on the network if you ping the network address or broadcast address. Many network admins are now filtering this out because it can be used to flood a system (check out smurf attacks).