Posted Thu, 01 Jan 2015 06:00:00 GMT by Portal Admin

Q. I performed an autodiscovery of my network and the status window of a device shows an unassigned .0 IP address, an HP printer's hostname, and a Sun's sysDescr. I confirmed the Sun has the correct .255 broadcast address, so I don't understand how InterMapper could have created this device.

A. This is because on Mac OS X, the .0 address is acting like the broadcast address. (Windows does not allow this, giving an error in the socket routine when we try to send the SNMP packet.)

The ifconfig output from a Mac on our network looks like this:

en0: flags=8963 mtu 1500
inet6 fe80::217:f2ff:fe03:d58c%en0 prefixlen 64 scopeid 0x4
inet 192.168.1.180 netmask 0xffffff00 broadcast 192.168.1.255

Which would indicate that the broadcast address is 192.168.1.255. But when 192.168.1.0 is pinged, it also acts like the broadcast address and gets responses from many servers on the network:

[cswmac:~] csw% ping 192.168.1.0
PING 192.168.1.0 (192.168.1.0): 56 data bytes
64 bytes from 192.168.1.15: icmp_seq=0 ttl=64 time=0.264 ms
64 bytes from 192.168.1.6: icmp_seq=0 ttl=64 time=0.273 ms (DUP!)
64 bytes from 192.168.1.40: icmp_seq=0 ttl=255 time=0.386 ms (DUP!)
64 bytes from 192.168.1.95: icmp_seq=0 ttl=255 time=0.391 ms (DUP!)
64 bytes from 192.168.1.207: icmp_seq=0 ttl=64 time=0.396 ms (DUP!)
64 bytes from 192.168.1.191: icmp_seq=0 ttl=64 time=0.400 ms (DUP!)
64 bytes from 192.168.1.7: icmp_seq=0 ttl=255 time=0.402 ms (DUP!)
...

You must be signed in to post in this forum.