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Contributor II
Posts: 70
Registered: ‎05-01-2015

What is the usage of vlan-pooling?

Hi guys,

 

I read the document about vlan-pooling taday,they said using vlan-pooling can reduce broadcast packets.

but even you use 2 vlans in one ssid, still the broadcast packets should cross the air every vlan has to 

wait for the difs time, so there is no different for 1vlan or 2 vlans.

 

I think the only different here is that the clients will handle the broadcast packets in layer 2 or layer 3.

Guru Elite
Posts: 21,029
Registered: ‎03-29-2007

Re: What is the usage of vlan-pooling?

Only dropping broadcasts truly reduces broadcasts. Vlan pooling could only help depending on how many users are in each vlan. Vlan pooling could also increase the number of broadcasts users are exposed to in vlans they do not belong to.


Colin Joseph
Aruba Customer Engineering

Looking for an Answer? Search the Community Knowledge Base Here: Community Knowledge Base

Contributor II
Posts: 70
Registered: ‎05-01-2015

Re: What is the usage of vlan-pooling?

Thanks, I'm totally agree with you, so the PPT about vlan-pooling was wrong, right?

Guru Elite
Posts: 21,029
Registered: ‎03-29-2007

Re: What is the usage of vlan-pooling?

Which PPT? Vlan pooling can reduce broadcasts depending on how it is configured and how many devices are in a single vlan. "Drop broadcasts and unknown multicast" just happens to reduce broadcasts better.


Colin Joseph
Aruba Customer Engineering

Looking for an Answer? Search the Community Knowledge Base Here: Community Knowledge Base

Contributor II
Posts: 70
Registered: ‎05-01-2015

Re: What is the usage of vlan-pooling?

From the ACMP training PPT.

I will send the pic tomorrow.

Contributor II
Posts: 70
Registered: ‎05-01-2015

Re: What is the usage of vlan-pooling?

And can you give me a scenario which vlan-pooling can reduce the broadcast packets?

Guru Elite
Posts: 21,029
Registered: ‎03-29-2007

Re: What is the usage of vlan-pooling?

An access point will only deliver broadcast traffic to an access point that has a user associated on that VLAN.  If you have  10 access points, and a single VLAN and a user associated on every access point, it has to deliver it to 10 access points.  If you use VLAN pooling and more than one VLAN in a pool, the access point would only have to deliver the traffic to the access points that have users on the VLAN with the broadcast, so statistically it could be less based on the fact that you would not have to deliver a broadcast to all users.  

 

After VLAN pooling was created a number of methods were introduced to control broadcasts like broadcast filter all, airgroup and dynamic multicast optimization that go even further than just statistically to drop broadcasts, so that VLAN pooling is not the most effective thing that can be used to control broadcasts.  Running broadcast and multicast applications on wireless and is very inefficient. You could just have "drop broadcast and multicast" enabled at the VAP level and use a single VLAN and not have to deal with any unwanted broadcasts.  Airgroup could also manage mdns and dlna traffic so that devices can discover each other without the broadcast overhead.  This is far more effective to control broadcasts than VLAN pooling.  VLAN pooling is still very good when you want to just add a VLAN capacity to a network without having to change subnet masks on all of your clients.



Colin Joseph
Aruba Customer Engineering

Looking for an Answer? Search the Community Knowledge Base Here: Community Knowledge Base

Contributor II
Posts: 70
Registered: ‎05-01-2015

Re: What is the usage of vlan-pooling?

Thanks a lot, now I can truely understand.

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