[j-nsp] Wishing for clarification on how dhcp-relay works with multiple server addresses

[Chuck Anderson]

On Fri, Jun 12, 2020 at 08:44:48AM +0300, Matti Saarinen wrote:
> Chuck Anderson <cra at WPI.EDU> wrote:
> 
> > On Thu, Jun 11, 2020 at 08:40:23AM +0300, Matti Saarinen wrote:
> >> We have a setup where one set of DHCP servers deliver IP configuration
> >> to clients and another set of DHCP servers deliver the PXE options. This
> >
> > Don't do that. Clients do not aggregate DHCP options from different
> > responses--they pick ONE DHCP server to bind to and use the info from
> > that one only. That's how the DHCP spec is written.
> 
> Actually, this setup has been working for years. I suppose the PXE code
> is more flexible in that matter. In any case, it worries me that we have
> been relying on a feature that may change without any notice when NIC
> firmwares are updated.
> 
> Back to my question:
> 
> Based on the forum responses[1] I'd say we have to live with the
> situation where we need to run dhcp-relay without forward-only on
> interfaces connecting networks needing PXE. The annoying issue is that
> every interface without forward-only eats one scale-subsrciber licence.

You can try using the legacy helpers configuration, but I'm not sure it works on MX10003:

set forwarding-options helpers bootp server x.x.x.x
set forwarding-options helpers bootp server y.y.y.y
set forwarding-options helpers bootp server z.z.z.z
set forwarding-options helpers bootp maximum-hop-count 16
set forwarding-options helpers bootp client-response-ttl 20
set forwarding-options helpers bootp interface xe-x/x/x.nnnn broadcast