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Community Member

Slow throughput between two VLANs

Hey everyone,

I'm having an issue that I have not been able to solve for a few months now. When transferring traffic between two VLANs my throughput rate seems to drop to about 1.5 - 3.0 megabits / second.

My setup is like this...

Two Nexus 5020 switches. (switch01 and switch02)

Two Nexus 2232PP fabric extender switches. (switch03 and switch04)

Two Dell R815s with Chelsio and Intel NICs. (host1 and host2)

The servers run Xenserver 6.0, but as part of testing with this I've tried installing RedHat 6.2, VMware ESX 5.0 (vsphere 5).

The issue occurs when using trunking and transferring data from one VLAN to another. Example...

VM1 is in VLAN401 with an IP address of The VM is on Host1.

VM2 is in VLAN402 with an IP address of The VM is on Host2.

I've been using a network throughput tool called iPerf to test and I find that I can only get a throughput rate of about 3.0megabits.

If I switch VM2 to be in VLAN401 with an IP address of I get a throughput rate of about 6.7gigabits/sec.

In the above scenario, I'm using a Layer3 interface on the Nexus 5020, but in production we use a Vyatta virtual firewall.

I worked with Citrix for about 3 months and that was a dead end.

Is there anyone out there who has seen a similar issue? Or has any ideas about this?



Cisco Employee

Slow throughput between two VLANs


Nexus 50XX series is completely L2 switch and all L3 operations either won't work at all or wil have reduced functionality (same as you see in your situation).

For L3 features (inter-vlan routing, hsrp etc) you need to use nexus 55XX with L3 daughter card.



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