Re: Anybody with experiences with managing more than one Power 10(or 11) server with one HMC - the local P10 and a remote P10 across the WAN?

That is the debate I am facing. One P10 in one DC has a physical HMC and
while it's in the same rack as the P10 I think the HMC port and the eBMC0
port are patched into a local switch. They have hard coded IP's The
second P10 is in another DC and here the HMC is virtual so it's somewhere
else in the data centre.  So traffic from that HMC has to be routed across
the corporate network to reach the P10. Both P10's are in different VLANs
and behind application firewalls.

The advice I have been given is, if I want the physical HMC (CR-1) to be
able to access the eBMC1 port on the remote P10, then I need both IP
addresses in the same VLAN so I have to stretch the VLAN across the two
DC's which our network team are reluctant to do. They are asking why can't
HMC at site B to site A traffic be routed over Layer 3 since we are not
relying on the remote HMC to act as a DHCP server for the P10 in site A.
This is apparently an enhancement to P10s and above.

On Sat, Aug 22, 2026 at 12:06 AM Rob Berendt <[email protected]>
wrote:

> As I reread your OP we do use physical IP addresses and not DHCP.
> I do believe they are on the same vlan.
>
> On Fri, Aug 21, 2026 at 7:58 AM Rob Berendt <[email protected]>
> wrote:
>
> > Here's the deal.  Many people think that the cord between your HMC and
> > your Power System needs to be dedicated and all three should be in a
> > concrete bunker.  They find it perfectly fine that your payroll data,
> > confidential engineering plans, nuclear launch codes, etc are on your
> > corporate network, but it's curtains for the free world if anyone can
> > access your HMC port on your Power System.  I disagree.
> > We have two Power Systems in Indy.  We have one Power system outside of
> > Grand Rapids MI.  We have no physical HMCs.  We use virtual HMC's
> instead.
> > The vHMC in GR can access all power systems in both locations.  The vHMC
> in
> > Indy can access all Power systems in all locations.  I believe you are
> > limited to 3 HMCs per power system.  The only time I hit that was when we
> > converted from two physical HMCs to two vHMCs and tried to have all four
> > active during the conversion.
> >
> >
> > On Thu, Aug 20, 2026 at 6:19 PM Barry Chu <[email protected]>
> > wrote:
> >
> >> I would like to be able to manage both a local Power 10 and a remote
> Power
> >> 10 (as a backup) across the WAN. The remote P10 has a local HMC already
> of
> >> course.
> >>
> >> Documentations suggests that the T1 (the second eBMC port on the Power
> 10)
> >> has to be in the same subnet as the HMC in the remote DC which means
> >> stretching the VLAN across the WAN.
> >>
> >> The port C0-T5-T1 in this diagram
> >>
> >> https://share.google/D2ucqvIEJe68Pr1BC
> >>
> >> Our network team is not keen on that and have asked why can't we use
> Layer
> >> 3 routing and not rely on the HMC being a DHCP server but use fixed IP.
> >>
> >> Anybody doing this and what are your experiences?
> >>
> >> Thanks
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