DHCP and our hosts

[Mike McGrath]

At present our physical hosts use DHCP and our Xen guests do not.  I'd 
like to do one or the other.  The only issue we have going completely 
DHCP is that hosts like the proxy boxes require some aliased 
interfaces[1] which isn't really a problem but it's a minor 
inconvenience if someone is looking through the dhcpd.conf file for free 
IP's.

Option 1:
Completely Static IP's, everywhere.  (Except for some network devices?)

Option 2:
Completely DHCP IP's, except for aliases or devices unable to use DHCP

Option 3:
Leave it as it is

Note: DHCP addresses are statically mapped, its not like bastion's IP 
address will change regularly.

Honestly I don't care but I'd vote for Option 2 because it requires the 
least amount of work / risk right now  Though if someone has a 
compelling reason for Option 1 or 3, let me know.

    -Mike


[1] AFAIK DHCP cannot be done on aliased interfaces because it shares a 
MAC with the physical interface.

[Mike McGrath]

Mike McGrath wrote:
>  At present our physical hosts use DHCP and our Xen guests do not. 
> I'd 
>  like to do one or the other.  The only issue we have going completely 
>  DHCP is that hosts like the proxy boxes require some aliased 
>  interfaces[1] which isn't really a problem but it's a minor 
>  inconvenience if someone is looking through the dhcpd.conf file for 
>  free IP's.
>
>  Option 1:
>  Completely Static IP's, everywhere.  (Except for some network devices?)
>
>  Option 2:
>  Completely DHCP IP's, except for aliases or devices unable to use DHCP 
One side
note about option 2, a more robust DHCP environment also allows 
for very useful pxe boot.

    -Mike

[seth vidal]

On Mon, 2007-03-12 at 16:01 -0500, Mike McGrath wrote:
>  Mike McGrath wrote:
>  > At present our physical hosts use DHCP and our Xen guests do not.  I'd 
>  > like to do one or the other.  The only issue we have going completely 
>  > DHCP is that hosts like the proxy boxes require some aliased 
>  > interfaces[1] which isn't really a problem but it's a minor 
>  > inconvenience if someone is looking through the dhcpd.conf file for 
>  > free IP's.
>  >
>  > Option 1:
>  > Completely Static IP's, everywhere.  (Except for some network devices?)
>  >
>  > Option 2:
>  > Completely DHCP IP's, except for aliases or devices unable to use DHCP
>  One side note about option 2, a more robust DHCP environment also allows 
>  for very useful pxe boot.
>   
what we've done here is:

dhcp to boot/pxe
and then we convert the dhcp info in %post of the kickstart to
static-info and drop it in the network config

so we don't have to rely on dhcp for everything and have a spof on the
dhcp server, but we can also use pxe/dhcp sensibly.

-sv

[Dennis Gilmore]

On Monday 12 March 2007 03:55:55 pm Mike McGrath wrote:
>  At present our physical hosts use DHCP and our Xen guests do not. 
> I'd
>  like to do one or the other.  The only issue we have going completely
>  DHCP is that hosts like the proxy boxes require some aliased
>  interfaces[1] which isn't really a problem but it's a minor
>  inconvenience if someone is looking through the dhcpd.conf file for free
>  IP's.
>
>  Option 1:
>  Completely Static IP's, everywhere.  (Except for some network devices?)
>
>  Option 2:
>  Completely DHCP IP's, except for aliases or devices unable to use DHCP
>
>  Option 3:
>  Leave it as it is
>
>  Note: DHCP addresses are statically mapped, its not like bastion's IP
>  address will change regularly.
>
>  Honestly I don't care but I'd vote for Option 2 because it requires the
>  least amount of work / risk right now  Though if someone has a
>  compelling reason for Option 1 or 3, let me know. 
I vote 2  with a comment in the
dhcpd.conf file stating what ips are staticly 
assigned and why.

-- 
Dennis Gilmore, RHCE

[Warren Togami]

Mike McGrath wrote:
>  At present our physical hosts use DHCP and our Xen guests do not. 
> I'd 
>  like to do one or the other.  The only issue we have going completely 
>  DHCP is that hosts like the proxy boxes require some aliased 
>  interfaces[1] which isn't really a problem but it's a minor 
>  inconvenience if someone is looking through the dhcpd.conf file for free 
>  IP's.
>  
>  Option 1:
>  Completely Static IP's, everywhere.  (Except for some network devices?)
>   
Isn't this the least error prone option?

(Each box keeps the correct network configuration during a failure of 
the DHCP server.  It cannot be disrupted by another DHCP server that 
could possibly come online, in a Xen guest or somewhere.)


Warren Togami
wtogami(a)redhat.com

[Benny Amorsen]

> >>>> "MM" == Mike McGrath
> <mmcgrath(a)redhat.com&gt; writes: 
MM> [1] AFAIK DHCP cannot be done on aliased interfaces because it
MM> shares a MAC with the physical interface.

The DHCP protocol apparently allows one MAC address to acquire several
IP addresses, with client identifiers. It looks like ISC DHCPD
supports that.

I haven't actually tried it.


/Benny

[Jerry Amundson]

On 13 Mar 2007 10:08:39 +0100, Benny Amorsen <benny+usenet(a)amorsen.dk&gt; wrote:
>  >>>>> "MM" == Mike McGrath
> <mmcgrath(a)redhat.com&gt; writes:
>
>  MM> [1] AFAIK DHCP cannot be done on aliased interfaces because it
>  MM> shares a MAC with the physical interface.
>
>  The DHCP protocol apparently allows one MAC address to acquire several
>  IP addresses, with client identifiers. It looks like ISC DHCPD
>  supports that. 
That'd be good. I'm inclined to use dhcp wherever possible...

jerry

-- 
"Oh joy! Rapture! I've got a brain"
-Scarecrow