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
On 02.08.2012 15:00, 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 > > > > _______________________________________________ > CentOS mailing list > CentOS at centos.org > http://lists.centos.org/mailman/listinfo/centosYou can (and are encouraged) to specify the NETMASK as well in that range file. I don't know why it uses that mask and broadcast; maybe it inherits them from other already configures interface? -- Sent from the Delta quadrant using Borg technology! Nux! www.nux.ro
From: Birta Levente <blevi.linux at gmail.com>> 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 ?Never used ifcfg-eth0-range, but did you try 49 to 54 instead of 48 to 55? $ ipcalc 192.168.1.48/29 Address:?? 192.168.1.48???????? 11000000.10101000.00000001.00110 000 Netmask:?? 255.255.255.248 = 29 11111111.11111111.11111111.11111 000 Wildcard:? 0.0.0.7????????????? 00000000.00000000.00000000.00000 111 => Network:?? 192.168.1.48/29????? 11000000.10101000.00000001.00110 000 HostMin:?? 192.168.1.49???????? 11000000.10101000.00000001.00110 001 HostMax:?? 192.168.1.54???????? 11000000.10101000.00000001.00110 110 Broadcast: 192.168.1.55???????? 11000000.10101000.00000001.00110 111 Hosts/Net: 6???????????????????? Class C, Private Internet JD
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-fbf00000That 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-0001.sig>
On 02/08/2012 17:24, Johnny Hughes wrote:> 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 > > > > > > > _______________________________________________ > CentOS mailing list > CentOS at centos.org > http://lists.centos.org/mailman/listinfo/centos >I have eth0 with public IP, netmask is 255.255.255.252. Additionally I own 8 public IPs xxx.xxx.xxx.48-55 with class subnet mask 255.255.255.248 If I set up with ifconfig eth:(0 to 7) xxx.xxx.xxx.(48-55) netmask 255.255.255.255 it's work. But if I set up the ifcfg-eth0:(0-7) files with the same IP and netmask it's not work. ifconfig show me the 255.255.255.252 netmask even if in file other netmask is specified. The same situation in ifcfg-eth0-range1 case. Thanks Levi
[For the archives, since I think Johnny just hit the wrong number key.....] On Thursday, August 02, 2012 10:24:27 AM Johnny Hughes wrote:> 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 192.168.1.64192.168.1.63 would be the correct broadcast address; .64 would be the network address of the next subnet.