Mailing List Archive: General IP settings question

General IP settings question

Aug 21, 2002, 11:10 AM

Post #1 of 3 (2039 views)

Theo wrote...
> You shouldn't be required to have any IPs on an interface for it to be
> used by wackamole. And it should work fine with two physical interfaces
> in the same subnet (though your routing table maybe confusing and/or
> wrong). If it doesn't work, there is a bug in wackamole.

Ok, I must have something fundamental confused. I'm missing something
IP-wise....Let me explain how I see it, and perhaps someone can tell me
where my thinking is FUBARed.

In a non-wackamole world, you don't put addresses on the same interface that
are in the same subnet UNLESS the additional (or 'alias') addresses use a
host subnet mask (255.x4). So I would think that if the interface you tell
wackamole to use already has a single non-VIP on it, it would have a
"normal" subnet mask of 255.255.255.0 for a class C. Then any additional
vip's that get assigned to that interface (in the same subnet) should have a
subnet mask of 255.255.255.255. Thus, I would think that the most common
settings for the netmask in wackamole.conf for a class C where the intf has
a nonVIP on it would be 255.255.255.255 yet all the docs I THINK show
255.255.255.0 for class C examples.

Case in point...
192.168.75.22 255.255.255.0 is the non-vip on int fxp0
Then, ANY addresses that wackamole puts on that interface (that are in the
same subnet) should not have a subnet mask of 255.255.255.0, it should be
255.255.255.255. Correct?

Another situation...
You have one interface (non-VIP) with 192.168.75.22 255.255.255.0 on it. You
want to use a different interface for all wackamole VIP's. How could you
possibly specify a correct netmask using the current wackamole parameters?
What I mean is, let's say you want 192.168.76.1-254 as VIP's on this 2nd
interface. Wackamole should assign the FIRST ip on this "blank" interface
with a subnet of 255.255.255.0, and any additional VIP's it throws on that
same interface should use 255.255.255.255. However, you can only specify a
single netmask in wackamole.conf. So while wackamole may go ahead and assign
the address & netmask, I would think it would be bizarre from an IP
standpoint.

So, am I really missing something here (very likely) or is wackamole only
designed to hand out IP's to an interface that already has a non-wackamole
IP address on it, and you would always specify 255.255.255.255 as your
netmask in wackamole.conf?

Thanks for any assistance to get me out of my confusion.

Jay West

---
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General IP settings question [ In reply to ]

jesus at omniti

Aug 21, 2002, 11:28 AM

Post #2 of 3 (1949 views)

Permalink

Jay West wrote:

>Theo wrote...
>
>
>>You shouldn't be required to have any IPs on an interface for it to be
>>used by wackamole. And it should work fine with two physical interfaces
>>in the same subnet (though your routing table maybe confusing and/or
>>wrong). If it doesn't work, there is a bug in wackamole.
>>
>>
>
>Ok, I must have something fundamental confused. I'm missing something
>IP-wise....Let me explain how I see it, and perhaps someone can tell me
>where my thinking is FUBARed.
>
>In a non-wackamole world, you don't put addresses on the same interface that
>are in the same subnet UNLESS the additional (or 'alias') addresses use a
>host subnet mask (255.x4). So I would think that if the interface you tell
>wackamole to use already has a single non-VIP on it, it would have a
>"normal" subnet mask of 255.255.255.0 for a class C. Then any additional
>vip's that get assigned to that interface (in the same subnet) should have a
>subnet mask of 255.255.255.255. Thus, I would think that the most common
>settings for the netmask in wackamole.conf for a class C where the intf has
>a nonVIP on it would be 255.255.255.255 yet all the docs I THINK show
>255.255.255.0 for class C examples.
>
>Case in point...
>192.168.75.22 255.255.255.0 is the non-vip on int fxp0
>Then, ANY addresses that wackamole puts on that interface (that are in the
>same subnet) should not have a subnet mask of 255.255.255.0, it should be
>255.255.255.255. Correct?
>
>
Correct. Your examples use fxp0 (which is FreeBSD).. and quoting from
the their man page:

alias Establish an additional network address for this
interface. This
is sometimes useful when changing network numbers, and one
wishes
to accept packets addressed to the old interface. If the
address
is on the same subnet as the first network address for this
interface, a netmask of 0xffffffff has to be specified.

However, the examples (I thought) referenced eth0 which is Linux. Linux
says nothing that I can find about bringing up VIPs with /32 netmasks.
In fact, the administrative tools for RedHat brings them up with a
netmask matching that of the subnet on which they reside.

--
Theo Schlossnagle
1024D/82844984/95FD 30F1 489E 4613 F22E 491A 7E88 364C 8284 4984
2047R/33131B65/71 F7 95 64 49 76 5D BA 3D 90 B9 9F BE 27 24 E7

General IP settings question [ In reply to ]

mag at newsof

Aug 21, 2002, 4:43 PM

Post #3 of 3 (1935 views)

Permalink

On Wed, Aug 21, 2002 at 02:28:20PM -0400, Theo Schlossnagle wrote:
> Jay West wrote:
>
> >Theo wrote...
> >
> >
> >>You shouldn't be required to have any IPs on an interface for it to be
> >>used by wackamole. And it should work fine with two physical interfaces
> >>in the same subnet (though your routing table maybe confusing and/or
> >>wrong). If it doesn't work, there is a bug in wackamole.
> >>
> >>
> >
> >Ok, I must have something fundamental confused. I'm missing something
> >IP-wise....Let me explain how I see it, and perhaps someone can tell me
> >where my thinking is FUBARed.
> >
> >In a non-wackamole world, you don't put addresses on the same interface
> >that
> >are in the same subnet UNLESS the additional (or 'alias') addresses use a
> >host subnet mask (255.x4). So I would think that if the interface you tell
> >wackamole to use already has a single non-VIP on it, it would have a
> >"normal" subnet mask of 255.255.255.0 for a class C. Then any additional
> >vip's that get assigned to that interface (in the same subnet) should have
> >a
> >subnet mask of 255.255.255.255. Thus, I would think that the most common
> >settings for the netmask in wackamole.conf for a class C where the intf has
> >a nonVIP on it would be 255.255.255.255 yet all the docs I THINK show
> >255.255.255.0 for class C examples.
> >
> >Case in point...
> >192.168.75.22 255.255.255.0 is the non-vip on int fxp0
> >Then, ANY addresses that wackamole puts on that interface (that are in the
> >same subnet) should not have a subnet mask of 255.255.255.0, it should be
> >255.255.255.255. Correct?
> >
> >
> Correct. Your examples use fxp0 (which is FreeBSD).. and quoting from
> the their man page:
>
> alias Establish an additional network address for this
> interface. This
> is sometimes useful when changing network numbers, and one
> wishes
> to accept packets addressed to the old interface. If the
> address
> is on the same subnet as the first network address for this
> interface, a netmask of 0xffffffff has to be specified.

From 4.6 man page for ifconfig:

alias - Establish an additional network address for this interface. This is
sometimes useful when changing network numbers, and one wishes to accept
packets addressed to the old interface. If the address is on the same
subnet as the first network address for this interface, a non-conflicting
netmask must be given. Usually 0xffffffff is most appropriate.

>
> However, the examples (I thought) referenced eth0 which is Linux. Linux
> says nothing that I can find about bringing up VIPs with /32 netmasks.
> In fact, the administrative tools for RedHat brings them up with a
> netmask matching that of the subnet on which they reside.
>
> --
> Theo Schlossnagle
> 1024D/82844984/95FD 30F1 489E 4613 F22E 491A 7E88 364C 8284 4984
> 2047R/33131B65/71 F7 95 64 49 76 5D BA 3D 90 B9 9F BE 27 24 E7
>
>
>
>
>
>
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