How does Bigip F5 LTM select which VM Adapter it assigns to the management interface

Sorry, I don't unederstand. Are you talking about the management interface to manage the BIG-LTP (normally the management interface does not route traffic) or you want a virtual server to use a different interface (NIC). When you create vlan, you decide on which interface adapter this vlan is seen.

if you are using vmware workstation, use the vmware network editor. Don't know your lab requirements but using all vNICs in bridge mode normally works :)

regards, hheredia

thanks for your answers. ok. sorry for the question. it seems what was causing all my pain was persistent udev rules. I thought it was the F5 somehow deciding what should be eth0 / mgmt all this time. thanks again for taking the time to consider my question.

sorry i answered prematurely. i am still stuck. the mgmt interface (net interface mgmt) is getting assigned to a certain mac-address. I want it to be assigned to a different mac address. i am trying to determine how it gets assigned. i have tried using persistent udev rules to force it to the mac address I want -but that didnt work. I have tried HWADDR in ifcfg-eth0 in /etc/sysconfig/network-scripts but that file gets auto-generated and that also fails. thanks in advance!

So we also virtualized our BIG-IPs, and we've run into issues with the order of the NICs. Typically when you first setup a BIG-IP, the software assumes the first NIC will be the mgmt NIC, which is typically eth0. Now where this gets tricky is when you go back and try to add NICs later on. There is a bug where the NICs can get completely reordered and that throws everything off. We've run into it before and I've got a few commands that can help with that if this is the case.

My first question would be are you setting up this BIG-IP for the first time or trying to add NICs after the fact?

THanks Brad. Sleepign on it, I came to the same thoughts. This is kind of an after--the-fact scenario. What commands did you have that helped? I'm definitely interested to hear.

I am also going to try another fresh install again and I'll post my findings here later today. Thanks again.

Also, if you are in a VMWare environment make sure the first NIC's type is set to 'Flexible' and subsequent NICs are set to VMXNet3.

The instructions below are ONLY if you are adding NICs to an existing deployment and you know for sure things are getting reordered. I'd test them in a lab environment before running them on your production. That is my only warning =)

First step for adding NICs after the fact in a virtual environment is to screenshot the hardware settings in your hypervisor so you can match the NICs to the MAC addresses after you make any changes. Do the same inside of the BIG-IP as well. When you do this in the BIG-IP document your VLAN settings as well, I've seen these get reordered as well.

Before bringing the BIG-IP down to add the NIC, run this command. touch /service/mcpd/forceload

Now bring the machine down and add the NIC.

Compare your documentation against what is currently running right now, check your pools and do some basic functionality tests, if everything looks good then you don't need to go any further.

If the NICs are out of alignment at this point, via the command line run 'rm /var/db/mcpd*' reboot and check the NIC alignment again. If things still aren't working right check your VLAN alignment in the web interface.

Also I will add that if you initially deploy your VM with all 9 NICs you won't run into this problem later on down the road as you eventually use those NICs. This all relates to VMWare so your experience with other hypervisors may differ.

I am using Oracle virtualbox. I found the answer. (or at least a workaround) chmand (chassy manager) on startup, inspects adapters and assigns to interfaces. chmand skips the adapter if it was set to Intel adapter type. saw it being inspected and skipped in /var/log/ltm. setting adapter 1 to PCnet-FAST III (Am79C973) it was inspected and selected as the management interface. Note, setting any other adapters to Am79C973 they would not be assigned to LTM interfaces - and your interfaces would be empty. Setting those to Intel PRO/1000 MT Server (8245EM) worked. I have not tried other adapter types - so the above solution may not be the only one. I also don't know why this works at this point.

further testing and I'm still getting inconsistent results. the adapter type doesn't seem to make a difference. sometimes chmand assigns the management interface to the correct adapter and sometimes it doesn't :(