Re: [gentoo-user] Re: static IP, gateway and netmask setting

[Etaoin Shrdlu <shrdlu@unlimitedmail.org>]

On Monday 26 November 2007, Dan Farrell wrote:

> you don't have to list the broadcast or netmask, if they can be
> guessed from context.  In the case of using a 192.168.x/24 network
> they can generally both be guessed properly, because that's a Class C
> private address .
>
> However, in the case of 10.0.0/24, this may not be true.  that is
> defined as class A private address space, and the networking utilities
> would probably assume it was 10.0.0/8, a netmask of 255.0.0.0 and a
> broadcast of 10.255.255.255.  That is what ifconfig does at least:
>
> pascal ~ # ifconfig eth0:1 10.0.0.1
> pascal ~ # ifconfig eth0:1
> eth0:1    Link encap:Ethernet  HWaddr 00:50:70:56:2E:CA
>           inet addr:10.0.0.1  Bcast:10.255.255.255  Mask:255.0.0.0
>           UP BROADCAST RUNNING MULTICAST  MTU:1500  Metric:1
>           Interrupt:225 Base address:0xc000

That is what ifconfig does, if you don't specify a netmask:

[root@mozart /x]# ifconfig eth0:1 10.0.0.1 netmask 255.255.255.0
[root@mozart /x]# ifconfig eth0:1
eth0:1    Link encap:Ethernet  HWaddr 00:11:2F:BB:F6:0D
          inet addr:10.0.0.1  Bcast:10.0.0.255  Mask:255.255.255.0
          UP BROADCAST RUNNING MULTICAST  MTU:1500  Metric:1
          Interrupt:17


I don't know exactly how initscripts work, but I suppose that if the /24 
is given in /etc/conf.d/net, then both the resulting iproute2 and 
ifconfig command that bring the interface up will include the netmask 
specification.
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