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The VLAN virtual port limit in release 1.4(1)


As per UCM 1.4 release notes the VLAN virtual port limit in release 1.4(1) is 6000. Any plans from Cisco to resolve this issue soon???

We have two UCS chassis which comprise of 16 B200M2 blades, two 6120XP Fabric Interconnect.

As per the network architecture we decided, all these blades were supposed to be part of one VMware vCenter Cluster and each blade to have 4 vNICs for carrying customer traffic. Each customer will get a separate VLAN for network isolation; that means to migrate the customer's VM anywhere across these 16 blades I need to configure his VLAN on all the blades and their vNICs.

But if I configure his VLAN on all the 16 blades I will be consuming 64 (16 blades x 4 vNIC/blade) VLAN virtual ports for one customer. Conversly, with 6000 VLAN virtual port I can have 6000/64 = 93 customers ONLY on 16 blade cluster with 12 Core CPU, 64GB Memory each.

We are running a public cloud for SMBs on this setup where customers comes up with average 2-3 VMs requirement with around 4GB memory; considering these numbers and 1:3 memory overcommitment we have 1TB (16 blades x 64GB) physical memory  and around 3TB with overcommitment.

That means the setup was expected to handle atleast around 300 customers or more but due to this VLAN virtual port limitations we are limitted to 93 customers (I haven't yet included VMware Mgmt VLANs)

I think UCS or rather vBlock is just good for private cloud and not public one unless VLAN virtual port limit issue is resolved.

2 Replies 2


Two days gone and no body from Cisco even care about this issue?


This limit from 3K -> 6K VLAN Ports was just increased in the 1.4 release.  I don't believe this is slated for further increasing in the next major release either. I'll check with development and confirm back. 

At first glance there appears to be some design concerns over scalability limiations.  If you're creating 4 vNICs per blade, you likely have different purposes for each vNIC correct? 

Ex. Management NIC, VMotion, VM traffic etc - in this case you do NOT need every VLAN on every NIC.  Prune your NICs to only the required VLANs and you'll find you can easily scale our a UCS infrastructure to support public cloud environments.  We have many public cloud providers with 20 chassis systesms that haven't been hindered by this VLAN port count.

If someone else wishes to chime in regarding design, feel free.



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