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

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CentOS mailing list CentOS@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

On 02/08/2012 17:52, Johnny Hughes wrote:

On 08/02/2012 09:33 AM, Birta Levente wrote:

...

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

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CentOS mailing list CentOS@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.

What if you do this:

ifcfg-eth0-range1: ONBOOT="yes" IPADDR_START="192.168.1.49" IPADDR_END="192.168.1.54" CLONENUM_START="1" BROADCAST=192.168.1.55 NETMASK=255.255.255.248 NETWORK=192.168.1.48

(with a .248 subnet, you can not use the first address (192.168.1.48) or the last address (192.168.1.55) on a device, they are the Network Address and the Broadcast Address ... so an 8 IP subnet has 6 usable addresses. Also, one of those 6 addresses will also need to be assigned to the gateway router if you need to talk to another network, so you really only have 5 addresses that you can assign for use).

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CentOS mailing list CentOS@centos.org http://lists.centos.org/mailman/listinfo/centos

Nope....

Work only .49 and .50

I bought 8 public IP-s ... so 8 IPs have to get work. In the hosting specification this IPs is usable with xxx.xxx.xxx.48-55 with subnet mask 255.255.255.255 with no gateway.

As I sad, works perfectly with this command (8 times, of course :) ): #ifconfig eth:(0 to 7) xxx.xxx.xxx.(48-55) netmask 255.255.255.255

Thanks

Levi

<snip>

Nope....

Work only .49 and .50

I bought 8 public IP-s ... so 8 IPs have to get work. In the hosting specification this IPs is usable with xxx.xxx.xxx.48-55 with subnet mask 255.255.255.255 with no gateway.

As I sad, works perfectly with this command (8 times, of course :) ): #ifconfig eth:(0 to 7) xxx.xxx.xxx.(48-55) netmask 255.255.255.255

Thanks

Levi

It doesn't work that way... You may think you bought 8 ip's, but you can only pass traffic on 6... That is how it works... You buy 16, and only 14 work. The first and last address are as Johnny said...

http://en.wikipedia.org/wiki/Classless_Inter-Domain_Routing

On 08/02/12 12:45 PM, Scott Silva wrote:

It doesn't work that way... You may think you bought 8 ip's, but you can only pass traffic on 6... That is how it works... You buy 16, and only 14 work. The first and last address are as Johnny said...

I've also seen DSL networks like this where those extra IPs are bridged not routed. in these cases, you use the same gateway as the 'main' IP, but usually the main IP has a /24 or whatever mask that encompasses ALL the IPs.

regardless, the OP should contact the ISP and find out what the mask and gateway are for the extra IPs.

On 02/08/2012 22:54, John R Pierce wrote:

On 08/02/12 12:45 PM, Scott Silva wrote:

...

It doesn't work that way... You may think you bought 8 ip's, but you can only pass traffic on 6... That is how it works... You buy 16, and only 14 work. The first and last address are as Johnny said...

I've also seen DSL networks like this where those extra IPs are bridged not routed. in these cases, you use the same gateway as the 'main' IP, but usually the main IP has a /24 or whatever mask that encompasses ALL the IPs.

regardless, the OP should contact the ISP and find out what the mask and gateway are for the extra IPs.

It's a bug in centos 6

http://bugs.centos.org/view.php?id=5391

PREFIX configured in ifcfg-eth0 is overrule the subnet mask in aliases.

Solution: removed PREFIX from ifcfg-eth0

Thanks to all

Levi

On 02/08/2012 22:45, Scott Silva wrote:

<snip> > Nope.... > > Work only .49 and .50 > > I bought 8 public IP-s ... so 8 IPs have to get work. > In the hosting specification this IPs is usable with xxx.xxx.xxx.48-55 > with subnet mask 255.255.255.255 with no gateway. > > As I sad, works perfectly with this command (8 times, of course :) ): > #ifconfig eth:(0 to 7) xxx.xxx.xxx.(48-55) netmask 255.255.255.255 > > Thanks > > Levi > It doesn't work that way... You may think you bought 8 ip's, but you can only pass traffic on 6... That is how it works... You buy 16, and only 14 work. The first and last address are as Johnny said...

http://en.wikipedia.org/wiki/Classless_Inter-Domain_Routing

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CentOS mailing list CentOS@centos.org http://lists.centos.org/mailman/listinfo/centos

Thank you all for your time ...

But I have another question:

Why is a difference in setting up with icfg-eth0:0 and ifconfig ? As I sad, setting up all 8 IP-s with ifconfig works perfectly. Why if I specify explicitly the subnet mask in ifcfg-eth0:0 then appear other?

Thanks

Levi

On 08/03/2012 08:54 AM, Lamar Owen wrote:

[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 192.168.1.64

192.168.1.63 would be the correct broadcast address; .64 would be the network address of the next subnet.

Indeed ... Thanks Lamar :-)