[CentOS] IP aliases for services (including dhcpd)?

[Mike Burger]

On 2015-04-22 3:57 pm, Les Mikesell wrote:
> On Wed, Apr 22, 2015 at 2:49 PM, David  Both
> <dboth at millennium-technology.com> wrote:
>> Yes confusion will abound. There should only ever be one and only one 
>> DHCP
>> server on any network. With two you will sooner of later have multiple 
>> DHCP
>> client hosts with the same IP addresses.
> 
> No, it's not going to give out duplicate IPs.  The dual servers are
> configured as primary/secondary and know about each other with some
> protocol to track what leases are already out.
> https://kb.isc.org/article/AA-00502/0/A-Basic-Guide-to-Configuring-DHCP-Failover.html
> My question is just about multiple IPs as aliases on the server side.
>  So far it looks like it is always sending with the same source IP
> even though it logs that it used the alias interface name.   I'm just
> wondering if it would confuse clients if it gets an IP from one source
> and subsequent ACKs from another.   But, I guess that has been
> happening for a long time already with the dual server setup.

This is normal behavior. When you have multiple IPs aliased on a system, 
they all answer for inbound, but the outbound traffic always shows the 
primary system IP as the source.

You might be able to finagle some sort of firewall SNAT rules to fake 
it, but I've never tried that, so I can't vouch for the viability of 
such a notion.
-- 
Mike Burger
http://www.bubbanfriends.org

"It's always suicide-mission this, save-the-planet that. No one ever 
just stops by to say 'hi' anymore." --Colonel Jack O'Neill, SG1