M and MSM Series

Clarification on VSC settings...

Regular Advisor

Clarification on VSC settings...

I thought I would post this because I recently became aware of how certain settings work on a VSC which are different than I had anticipated.   The HP documentation on this is not very precise and l was surprised by my testing/results using Wireshark.  Feel free to disagree if you have found something to the contrary with your own testing/results.!



Broadcast Filtering (Enable/Disable)


What I thought occurs -- I asssumed that enabling this option would prevent ANY broadcasts being sent from an AP to a wireless client.  This is NOT true at all. 


What actually occurs -- With this option enabled, broadcasts coming from the WIRED network are STILL sent to the wireless clients and are NOT filtered at all.  So, for example, if your wireless clients share the same network/vlan as any wired devices, all broadcasts FROM any wired devices will still be sent TO the wireless clients.  This setting ONLY attemps to filter broadcasts when they are coming FROM a wireless device.  Furthermore, while enabling this option greatly reduces broadcasts coming FROM a wireless client TO another wireless client, it does NOT filter all broadcasts.  My packet captures show that broadcasts for things like NBNS queriers (name queries) and MS browser announcements (master browser, etc.) are not filtered correctly and still passed along to all wireless clients.



Allow traffice between [No] wireless clients


What I thought occurs -- I assumed this setting would just block traffic coming from a wireless device specifically sent to another wireless device. 


What actually occurs -- With this setting, not only is traffic blocked that is coming FROM a wireless device specifically sent TO another wireless device (such as a direct ping packet), but this ALSO attemps to block/filter broadcast traffic FROM a wireless device going TO another wireless device.  In other words, it blocks more than just direct communication.  Which is rather confusing because there's already a different checkbox/option for Broadcast Filtering.



For some, this may not be a big deal... for others, it might be, especially since the HP documentation does NOT address this specifically and can lead to incorrect assumptions. I hope HP clears this up with documentation or how they term these settings in the VSCs.   According to my conversation with Level 3 tech and a developer, this is by design but poorly documented. (?)    Passing along my findings for those who might be interested.







Jesse R
Source One Technology, Inc.
HP Partner

MSM 5.7.x deployment guide: