On 08/02/2012 09:00 AM, Birta Levente wrote: > Hi all > > Can someone explain me this: > > ifcfg-eth0-range1: > ONBOOT="yes" > IPADDR_START="192.168.1.48" > IPADDR_END="192.168.1.55" > CLONENUM_START="1" > > Why Bcast is 192.168.1.51 and why Mask is 255.255.255.252 ? > > OS: Centos 6.3/64bit > > > Thanks > > Levi > > # ifconfig > > eth0:1 Link encap:Ethernet HWaddr 00:9C:02:99:FA:00 > inet addr:192.168.1.48 Bcast:192.168.1.51 Mask:255.255.255.252 > UP BROADCAST RUNNING MULTICAST MTU:1500 Metric:1 > Interrupt:16 Memory:fbee0000-fbf00000 > > eth0:2 Link encap:Ethernet HWaddr 00:9C:02:99:FA:00 > inet addr:192.168.1.49 Bcast:192.168.1.51 Mask:255.255.255.252 > UP BROADCAST RUNNING MULTICAST MTU:1500 Metric:1 > Interrupt:16 Memory:fbee0000-fbf00000 > > eth0:3 Link encap:Ethernet HWaddr 00:9C:02:99:FA:00 > inet addr:192.168.1.50 Bcast:192.168.1.51 Mask:255.255.255.252 > UP BROADCAST RUNNING MULTICAST MTU:1500 Metric:1 > Interrupt:16 Memory:fbee0000-fbf00000 > > eth0:4 Link encap:Ethernet HWaddr 00:9C:02:99:FA:00 > inet addr:192.168.1.51 Bcast:192.168.1.51 Mask:255.255.255.252 > UP BROADCAST RUNNING MULTICAST MTU:1500 Metric:1 > Interrupt:16 Memory:fbee0000-fbf00000 > > eth0:5 Link encap:Ethernet HWaddr 00:9C:02:99:FA:00 > inet addr:192.168.1.52 Bcast:192.168.1.51 Mask:255.255.255.252 > UP BROADCAST RUNNING MULTICAST MTU:1500 Metric:1 > Interrupt:16 Memory:fbee0000-fbf00000 > > eth0:6 Link encap:Ethernet HWaddr 00:9C:02:99:FA:00 > inet addr:192.168.1.53 Bcast:192.168.1.51 Mask:255.255.255.252 > UP BROADCAST RUNNING MULTICAST MTU:1500 Metric:1 > Interrupt:16 Memory:fbee0000-fbf00000 > > eth0:7 Link encap:Ethernet HWaddr 00:9C:02:99:FA:00 > inet addr:192.168.1.54 Bcast:192.168.1.51 Mask:255.255.255.252 > UP BROADCAST RUNNING MULTICAST MTU:1500 Metric:1 > Interrupt:16 Memory:fbee0000-fbf00000 > > eth0:8 Link encap:Ethernet HWaddr 00:9C:02:99:FA:00 > inet addr:192.168.1.55 Bcast:192.168.1.51 Mask:255.255.255.252 > UP BROADCAST RUNNING MULTICAST MTU:1500 Metric:1 > Interrupt:16 Memory:fbee0000-fbf00000 That is obviously not going to work ... a 255.255.255.252 mask is a 4 IP subnet, with only 2 usable addresses and a network number and a broadcast address. The only free addresses in 192.168.1.48/255.255.255.252 are .49 and .50 The Broadcast and Mask settings are likely in your ifcfg-eth0 file and not in the range file at all. The Mask would either be set manually in ifcfg-eth0 ... or by the DHCP server if you get DHCP. The Broadcast address would automatically be set based on the Mask, unless it is overridden in ifcfg-eth0. If the address is set via DHCP, you need to change the subnet mask on the DHCP server as that is where it comes from. If you want 8 usable addresses (including the Network number, a gateway address, and a Broadcast address), that would mean you need at least 11 IPs in that subnet ... the closest fit would be a 255.255.255.240 subnet (which has 16 addresses). If you were to want to use th 255.255.255.240 subnet, then 192.168.1.48 would not be available as it would the the Network number for that subnet ... the usable addresses would be 192.168.1.49-63 that case and the Broadcast Address would be 192.168.1.64 Since this is on a private network, why are you not just using the full 192.168.1.0 network with a 255.255.255.0 subnet? I guess the real question is, what are you trying to do :D -------------- next part -------------- A non-text attachment was scrubbed... Name: signature.asc Type: application/pgp-signature Size: 262 bytes Desc: OpenPGP digital signature URL: <http://lists.centos.org/pipermail/centos/attachments/20120802/624743ad/attachment-0004.sig>