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Re: IP aliasing

Steven M. Bellovin wrote:

On Wed, 18 Jun 2008 16:57:01 +0100
Patrick Welche <prlw1%cam.ac.uk@localhost> wrote:


On Wed, Jun 18, 2008 at 10:00:10AM -0400, DAve wrote:

Good morning,

I have been told by my Network Administrator that we will be
changing IP blocks for several key services very soon. I have three
new DNS servers running NetBSD on the new IP block already. I also
have two legacy DNS servers (also on NetBSD) that I need to drag
along behind me for a few more months.

My new IP block is 65.124.104.X and my old IP block is
65.196.224.X. Is it possible to have a single machine answer for
both IPs on a single interface? The network Gods claim they can
route the traffic to me no problem, but I am unsure how to
configure the alias for the interface.

Old address: 65.196.224.2
Netmask: 255.255.255.0
Gateway: 65.196.224.1

New address: 65.124.104.25
Netmask: 255.255.255.224
Gateway: 65.124.104.1

Is it even possible to alias the old address with the new gateway?

        ifconfig if0 inet 65.124.104.25 netmask 255.255.255.224
        ifconfig if0 inet 65.196.224.2 netmask 255.255.255.0 alias

should do the trick? (replacing if0 with bge0 wm0 nfe0 or whatever
you have)

Your gateway is a specific router, so what is its ip number?
65.124.104.1?

        route change default 65.124.104.1

for the outbound traffic?


Right, but that can't coexist with the old setting; you can only have
one default route, I believe. 

This works,
route delete default;route add default 65.124.104.1
I appreciate the response, it just doesn't look like it should work to me. I will give the following a try. 

ifconfig hme0 65.124.104.25 netmask 255.255.255.224
ifconfig hme0 alias 65.196.224.2 netmask 255.255.255.0

and remember to change my named.conf as well ;^)

DAve

--
Don't tell me I'm driving the cart!
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