Strange network problem

[Brian Densmore]

Sorry, I mistyped.

Right the mask is 255.255.255.0
and the broadcast is 172.21.12.255

I'm not at the machine right now, but
route returns something like this:

172.21.12.0		*	255.255.255.0	U	0	0	eth0
default	172.21.12.1	0.0.0.0		UG	0	0	eth0

and ifconfig returns something like:

eth0      Link encap:Ethernet  HWaddr xx:xx:xx:xx:xx:xx
          inet addr:172.21.12.2  Bcast:172.21.12.255  Mask:255.255.255.0
          UP BROADCAST RUNNING MULTICAST  MTU:1500  Metric:1
          RX packets:0 errors:0 dropped:0 overruns:0 frame:23
          TX packets:193 errors:0 dropped:0 overruns:0 carrier:0
          collisions:0 txqueuelen:100
          RX bytes:0 TX bytes:6348 
          Interrupt:x Base address:0xxxxx

lo        Link encap:Local Loopback
          inet addr:127.0.0.1  Mask:255.0.0.0
          UP LOOPBACK RUNNING  MTU:16436  Metric:1
          RX packets:32 errors:0 dropped:0 overruns:0 frame:0
          TX packets:32 errors:0 dropped:0 overruns:0 carrier:0
          collisions:0 txqueuelen:0
          RX bytes:5528 (5.3 KiB)  TX bytes:5528 (5.3 KiB)

or 
eth0      Link encap:Ethernet  HWaddr xx:xx:xx:xx:xx:xx
          inet addr:172.21.12.2  Bcast:172.21.12.255  Mask:255.255.255.0
          UP BROADCAST RUNNING MULTICAST  MTU:1500  Metric:1
          RX packets:0 errors:0 dropped:0 overruns:0 frame:1
          TX packets:0 errors:93 dropped:0 overruns:0 carrier:0
          collisions:0 txqueuelen:100
          RX bytes:0 TX bytes:6348 
          Interrupt:x Base address:0xxxxx

lo        Link encap:Local Loopback
          inet addr:127.0.0.1  Mask:255.0.0.0
          UP LOOPBACK RUNNING  MTU:16436  Metric:1
          RX packets:32 errors:0 dropped:0 overruns:0 frame:0
          TX packets:32 errors:0 dropped:0 overruns:0 carrier:0
          collisions:0 txqueuelen:0
          RX bytes:5528 (5.3 KiB)  TX bytes:5528 (5.3 KiB)

> -----Original Message-----
> From: Gerald Combs [mailto:gerald at zing.org]
> Sent: Monday, August 23, 2004 12:10 PM
> To: Brian Densmore
> Cc: KCLUG (E-mail)
> Subject: Re: Strange network problem
> 
> 
> Brian Densmore wrote:
> 
> > netmask is 172.21.12.255 which is correct.
> 
> It is?  Subnet masks are nearly always a string of ones, followed by a
> string of zeroes, e.g. "255.255.255.0".  The ones indicate 
> which bits in
> an address designate the subnet part, and the zeroes indicate 
> which bits
> in an address designate the host part.  "172.21.12.255" looks an awful
> lot like a broadcast address on a network with a 24-bit netmask.
>