@mverlis wrote:
I've read a few posts in airheads on the vlan pool vs. large subnet topic but they seemed more focused on smaller networks. (10 pools at most and /24's) So I am posting to get opinions.
Currently on my network:
It is a single campus
peak time concurrent clients are around 20,000
In the 6 months I have been running airwave I have seen 75,000 client devices
We currently do vlan pooling, we have 26 /22 subnets in the pool.
We do not allow inter client communication
We convert all bcast/mcast to unicast
there is only one class of wireless user
the number of devices is always creeping upwards
We are doing a large upgrade to 7200 series controllers so we now have an opportunity to revisit the vlan pooling / large subnet question. Moving to a large subnet would simplify a lot of configurations and make it easier to look at.
Would a /15 subnet be too large and not recommened (we have no intention over ever allowing interclient communications or enabling bcast/mcast)? (when I think about switched networks it just feels extremely wrong...)
Airplay is something we may consider in the future.
If you have a large campus and evaluated vlan pools versus the large subnet, why did you choose one over the other?
Would Aruba NOT recomened a large flat subnet in this case?
Thanks,
mverilis,
I am going to paraphrase someone who I have been speaking to about this topic lately who has been doing testing with large subnets. Here is what he suggests:
- Turn on bcmc optimization on that VLAN on every controller hosting that VLAN.
- Make sure broadcast filter all and broadcast filter ARP are enabled on that Virtual AP
- Make sure that wireless VLAN does not have wired users in it
- On the wireless side, the incoming broadcast and multicast from a client is first unicast to the AP/controller which then can determine what to do with the packet, so there is inherent flow control over there
-Tthe ability for a client to generate uncontrolled bc/mc is limited by the wireless bandwidth that this particular device can get.
There are also benefits from moving to a single VLAN such as:
- Not fragmenting IP address space, not running out of space in a VLAN that the pooling hash assigns a user to while there are free spots available in other VLANs - i.e., make more efficient use of address space without a whole lot of planning.
- No L3 mobility issues
- IPv6 deployment becomes much simpler with a single VLAN - only one RA to be advertised to the entire user population across all APs and these can be simply multicast
Your main consideration is your switching fabric needs to be able to handle all those mac addresses in its table.
This is certainly cutting edge deployment, so if you want us to have someone talk to you about this, please let me know. (please don't corner your Aruba SE).