Thanks for the advice. I think I am going to have to do it with 2 cards.
We have a new provider and a new T1 line that we are switching to. So, we
have a new router for that line and everything. So, I will need the IP's
on both networks to be active at the same time. So, when I do the DNS
switch, they will both be active while all the other DNS servers refresh
to the new IP's.
Thanks,
Bryan Opfer
On Tue, 2 Jun 1998, William T Wilson wrote:
> On Tue, 2 Jun 1998 [EMAIL PROTECTED] wrote:
>
> > We are in the process of changing Networks. And I need a way to switch
> > our web machines from one network to the other with no downtime. At first
> > we were going to mirror the machines on both networks. But, i think there
>
> That would work. In the case of a physical disparity between the networks
> (i.e. they are different wires) that is the only way to do it with zero
> downtime, since you would have to shut off your computer to change the
> ethernet card.
>
> If you are only changing network numbers, not physical networks, you can
> do this easily.
>
> If you are not changing technologies, but only wires (i.e. you are going
> to unplug one ethernet wire from your card and plug a different one in but
> you don't need a new network card) then you can combine the following two
> strategies to get, if not exactly zero downtime, a downtime of only a few
> seconds.
>
> > is a better way. Could I add a second ethernet card to the machines and
> > set it up for the new network? That way he same machine is on both
>
> That's going to imply some downtime, isn't it. :)
>
> If you are simply renumbering your existing Ethernet, you can simply add
> another IP address (and netmask, etc.) to your existing Ethernet card so
> it talks on both networks at once. Then when you shut off the other
> network, you simply remove the old IP address.
>
> In this case you will need to make use of IP-aliasing. I don't know if
> this capability can be loaded as a module (I don't think it can) or, if
> not, whether Red Hat's default kernel comes with it. If it doesn't, or if
> you compiled your own but without the IP-aliasing option, you will not be
> able to do it this way. You would have to at the very least recompile
> your kernel and reboot.
>
> If you have IP aliasing, you can use something like
> ifconfig eth0:0 10.23.54.2 netmask 255.255.255.0
> That would add the 10.23.54.2 IP address to the eth0 card, with the given
> netmask, it should be able to guess the rest of the data it needs
> automatically.
>
> If you mean you are physically changing networks (10baseT to 100baseT, for
> example) then you could do as you suggested before and install a new
> network card, using them both at once. But you need to use kernel
> commandline options, or manually load your network card drivers as
> modules, so it can see both ethernet cards at once. And of course you
> have to shut down to put in the new card.
>
> If you are changing networks but not technologies, then you can add the
> network alias to your network card ahead of time. Now your network card
> has a valid address for the network it is on, and a valid address for the
> network it is going to be on. But the numbers for one network are not
> valid for the other one. After you have this set up, simply swap your
> network cable out. You don't have to even reboot or shut off the
> computer. Now all of a sudden the valid IP becomes invalid and the
> invalid one becomes valid. But if no one tells your computer, it won't
> even notice. :) You can then safely remove the old, now invalid, IP
> address.
>
> > networks. Also, would Apache have probalems with this?
>
> No. You don't even have to restart httpd.
>
>
> --
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