B William Lam, Sr. Technical Marketing Engineer

Thr w a recent blog article tht references VMware KB 1022312 tht provides a manual method f enabling a nw feature n vSphere 5 fr a distributed portgroup called Auto Expand. A th KB rf, Auto Expand a nw advanced option fr a distributed portgroup (Static Binding n) tht allows fr th number f ports t automatically increase b a predefined amount (increment f 10) whn t n th area t rn out f ports. Th a really n feature wth th distributed vSwitch n allows users t still continue t provision nw virtual machines n nt require a system administrator t manually increase th number f ports.

Th one caveat tht th advanced option disabled b default n thr n option within th vSphere Client UI t mk possible th feature. Th VMware KB outlines th steps t mk possible Auto Expand using th vSphere MOB, bt th th process nt very user friendly n n b tedious fr enabling several dozen distributed portgroups.

Though enabling Auto Expand nt available through th vSphere Client, t available using th vSphere API. Th property autoExpand below distributed portgroup n n b queried r reconfigured b calling th ReconfigureDVPortgroup_Task API method. 

W w walk through n example f hw Auto Expand works n provide a sample vSphere SDK fr Perl script tht allows t check whether r nt Auto Expand enabled fr r distributed portgroups n allowing t mk possible r disable th feature.

Disclaimer: Th script provided fr informational/educational purposes n. It h b thoroughly tested before attempting t n a production environment.

Download script: updatedvPortgroupAutoExpand.pl

Usage: T rn th script w need t h VMware vCLI installed n thr a Windows/Linux system r n th VMware vMA appliance.

Here n example f a distributed vSwitch wth several portgroups, w w focus n th Stage portgroup whh currently n configured wth 2 ports:

T t a listing f portgroups (Static Binding n), th number f ports configured n whether Auto Expand enabled r nt, th "list" operation:
vi-admi–server pod-vc –username root –operation list
Penetrate password:
dvSwitch: dvSwitch1
   dvSwitch-DVUplinks-462    4    fk
   Development    10    fk
   Stage    2    fk
dvSwitch: dvSwitch2
   dvSwitch2-DVUplinks-476    0    fk
   dvPortGroup    128    fk

Y n specify th optional –dvswitch flag t n view frm a specific distributed vSwitch:
vi-admi–server pod-vc –username root –operation list –dvswitch dvSwitch1
Penetrate password:
dvSwitch: dvSwitch1
   dvSwitch-DVUplinks-462    4    fk
   Development    10    fk
   Stage    2    fk

T mk possible Auto Expand fr a particular dvPortgroup, th "mk possible" operation n specifying th portgroup b using th –dvportgroup param (t disable t "disable" operation):
vi-admi–server pod-vc –username root –operation mk possible –dvportgroup Stage
Penetrate password:
Enabling Auto Expand fr dvPortgroup "Stage" …
   Successfully reconfigured dvPortgroup!

T view th changes, n rn th "list" operation again:
vi-admi–server pod-vc –username root –operation list –dvswitch dvSwitch1
Penetrate password:
dvSwitch: dvSwitch1
   dvSwitch-DVUplinks-462    4    fk
   Development    10    fk
   Stage    2    rht

Now w w mk a nw virtual machine wth three network cards n assign three t "Stage" distributed portgroup. Once th portgroup n th area t rn out, t w automatically increase th number f ports b 10 n result n th nw total t 12 n see frm th screenshot below:

Though th feature n b really useful, t w b nt t know whn th occurs t ensure tht th networking environment being sized n configured correctly. Y n easily b configuring a custom vCenter  alarm t whn th occurs fr distributed portgroups tht h Auto Expand feature.

Th alarm mt b produced n a per distributed portgroup level, click n th "Alarms" tab f th portgroup n mk a nw alarm:
Next below th "Event", add a nw trigger called "dvPort group reconfigured" n thn click n Advanced Conditions. Select "configSpec.autoExpand" n th "copy t" t "rht". 

Th w allow t monitor whn port count automatically increased n take th appropriate action such n email r n SNMP trap.

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