Moving VIOS, LPAR's, HMC to different subnet

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Operating Systems AIX Moving VIOS, LPAR's, HMC to different subnet
# 1  
Old 03-13-2014
Moving VIOS, LPAR's, HMC to different subnet

Just joined to new company with one Power 720 Express (8202-E4C) server and have no much experience with IBM systems.
I am trying to move everything I mentioned to different subnet as required by customer contract (currently sitting on same subnet as company lan). Access to this subnet will be controlled by firewall (dedicated physical port).
My idea was first to move HMC than VIOS and LPAR's at the end. Through HMC I could use console access to VIOS and LPAR's so I can control IP settings not worrying losing connectivity to them.
First I moved HMC (management) port and it works as expected (I can access it from old subnet).
Problem is that HMC now can not connect with console to VIOS and LPAR's any more. (Internal error, unable to send command to the managed system)
So my question is how HMC communicates with VIOS and LPAR's?
How can I ensure not to lose console access capability?
Do I just need to configure VIOS and LPAR's with IP's from new subnet and hope that they would be accessible again via console access?
For HMC move I changed IP address and default route on interface. On firewall side for the transition period both subnets can talk to each other - no restriction/blocking).

Last edited by spricer; 03-14-2014 at 10:44 AM.. Reason: more details
# 2  
Old 03-14-2014
How is your HMC connected to the p720?

It will either be a direct connection from the HMC to the port labelled HMC1 or HMC2 on the p720 or you are going through the network.

The ports labelled HMC1 & 2 on the p720 may be DHCP or fixed addresses. Do you know?

I have a server that I can't get the console to too. No error is returned though. Smilie

Thanks, in advance,
# 3  
Old 03-14-2014
HMC and FSP are directly connected.:
-HMC (eth0 - first picture w w

remove emty space between w w w
-FSP (HMC1 - search for 8202-E4C on the same page)

I think HMC port on FSP has fixed IP address.

What puzzles me is that I thought that by established direct HMC to FSP connection your console access to VIOS and LPAR's is guaranteed. What I really did is just switched management port for HMC (eth1 on mentioned page) to new subnet.
So conclusion is that HMC management port ip address has to be on the same subnet as VIOS and LPAR(s) or maybe I need to adjust route settings...
There must be some info of having HMC management port on different subnet but I could not find it yet.
Also if anybody knows how can I check if SEA was set with IP address?

Last edited by Neo; 11-21-2017 at 02:13 AM..
# 4  
Old 03-14-2014
Ok so you are doing open network connection,
I rather say use private IP between HMC and Manage system (ie.e use DHCP)
In the HMC go to HMC management --> change network settings --> LAN Adapter (Mostly people use eth0 for private IP, I don't know how you configured)--> Details --> (Select Private) - Autodetection -- DHCMP Server (enable) -- OK.

Do the connectivity test.

Also, if your HMC and VIOS are NOT on same VLAN you don't even have to worry about changing the IP of HMC, you use public IP to get into HMC.

Also, make sure to ask if network is tagged, if so you have to change the PVID as per the new subnet.
If you there is No VLAN Tagging then the setup is as you have now.

Hope this helps.
# 5  
Old 03-14-2014
Maybe I don't understand network settings completely:
In HMC's network settings currently there are two adapters with next :
-eth0 (assuming direct connection to FSP) , Private, Autodetection, enabled DHCP server (, greyed out settings for IPv4 (
-eth1 (assuming management port), Open, Autodetection, DHCP disabled, IPv4,
Routing settings: Default Gateway for eth1
No tagging involved.
VIOS and LPAR;s are on same subnet as eth1.

Now I figured that default gateway has to be the same one that of VIOS and LPAR's are using in order for HMC to connect to them via console.
You are right that IP settings for eth1 does not matter but than I can not reach remotely HMC unless I change route, which in turn makes problem for HMC accessing LPAR's via console.
Now I tried attaching cable to eth2 and connecting it to new subnet, added static NET route,, for eth2 and everything works fine ( is new subnet gateway). I can remotely access HMC and still HMC can access LPAR's via console.
So my question now is if you missconfigure IP settings on VIOS how can I access missconfigured system or better question how you can access VIOS that does not have network interface? e.g. in KVM I do not care about network settings at all as long as I have physical access to hypervisor (I can access guests via console).
# 6  
Old 03-14-2014
Ok, that means eth0 (192.168.128.X) is the private network (which communicates with all Manage systems).

Eth1 is your public IP (which you use to establish connection from putty or web).
Unless you do VLAN Tagging or give a dedicated ethernet card to LPAR, they have to be on same subnet as your VIO

"Now I figured that default gateway has to be the same one that of VIOS  and LPAR's are using in order for HMC to connect to them via console".

This sentence is not really true, because the connection to Manage systems is through Private network and that is the reason you see Manage systems with different subnets are connected to HMC. (my personal example, I have my HMC on 10.10.4.x network and my MS on 4.x and 170.x)

Ok, if your eth2 configuration worked, then something must be wrong with eth1 configuration (either gateway or subnet mask values), or may be that IP is conflicting with other host.
We need more details on this to understand and troubleshoot.

Once you are in HMC, you will use console to get into VIO/LPAR, but in order to reach HMC you configure Public IP (in your case eth2).

So, once you are connected to HMC, then you use console to get to VIOS/LPAR.

Look at the network topology (from HMC under HMC management select that), you should see eth0 as the interface for all connections.

Hope this helps.
# 7  
Old 03-14-2014
This sentence is not really true, because the connection to Manage  systems is through Private network and that is the reason you see Manage  systems with different subnets are connected to HMC...

I understand that private network is used to manage FSP's and let's forget remote access to HMC (I will work directly on HMC hardware in server room). Question is why I cannot access VIOS via HMC console if I change default gateway for eth1 in Network settings? (this automatically starts another question what would happen if I put wrong network parameters in VIOS, how am I suppose to access it?).
A well configuration of eth2 (reverted everything back) does not guarantee that I will have access to VIOS if I missconfigure it (according to the problem on eth1).
What I would like to see is that I can access VIOS from HMC (hardware side) via console no matter of eth1 settings, or default gateway. Currently this is not case if I change dafault gateway.
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