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Old 08-02-2012, 02:00 PM
Birta Levente
 
Default IP range

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



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Old 08-02-2012, 02:12 PM
Nux!
 
Default IP range

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@centos.org
> http://lists.centos.org/mailman/listinfo/centos

You 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
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Old 08-02-2012, 02:18 PM
John Doe
 
Default IP range

From: Birta Levente <blevi.linux@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
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Old 08-02-2012, 02:24 PM
Johnny Hughes
 
Default IP range

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




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