[CentOS] Problem changing server on a LAN

[Les Mikesell]

On 6/6/11 7:13 PM, Timothy Murphy wrote:
> Les Mikesell wrote:
>
>>> I'm having great difficulty trying to change server on my home LAN.
>>> At present 192.168.2.2 is my server, running CentOS-5.6
>>> and connecting to an ADSL modem.
>>> I want to change server to another CentOS machine, 192.168.2.5 .
>>> The problem is that I cannot get the computers on the system
>>> to forget the old server, even when it is completely disconnected,
>>> and the new server is connected to the modem.
>>>
>>> It seems extraordinarily difficult to get rid of the link
>>> to the old server.
>>> Even when all the machines are re-booted they still
>>> want to give 192.168.2.2 as their default gateway.
>>>
>>> Is this a problem often met in this kind of situation?
>>> I'm wondering if it would be simpler to give the old address
>>> to the new server?
>>
>> I assume the computers with this problem have their IP and associated
>> (gateway/netmask) info configured by DHCP since if they were set up
>> manually you'd probably remember what to change...
>>
>> So, what machine is acting as the DHCP server, has it been updated with
>> the new gateway info, and what was the old lease time for the
>> outstanding assignments?
>
> Thanks for your response.
> I'm pretty sure the problem lies in the dhclient leases, as you suggest.
> I'm never quite sure if one can delete leases one doesn't like?
>
> I tried with dhcp running on both old and new server.
> But my dhcpd.conf doesn't contain anything about the gateway.
> Could it? And if so, how exactly?
>
> Now I look more carefully, I see there is a line
> 	option routers    192.168.2.2;
> in /etc/dhcpd.conf ;
> and I copied that to the new server.
> I guess that probably is the cause of the problem;
> if so, thank you very much.

Yes, option routers is what sets the client default gateway.  If you change it 
on the server the clients will pick it up when their lease expires - and 
normally on a reboot.

> Just to tell the full story;
> I (or rather Windows) destroyed the partition table on my old server,
> though it continues to run perfectly.
> I've re-written the table from the information given by lshal ,
> but I have no great confidence in my reasoning ,
> and suspect the disk may become unreadable when I re-boot.
> So I'm trying to set up an alternative server.

If you want to replace the old one, just give it the same ip address.

-- 
   Les Mikesell
    lesmikesell at gmail.com