Showing results for 
Search instead for 
Did you mean: 

Disjoint Layer 2 Uplink



Disjoint layer-2 networks are required if you have two or more Ethernet “clouds” that never connect, but must be accessed by servers or virtual machines located in the same Cisco UCS domain. The configuration for disjoint L2 networks works on a principle of selective exclusion. Traffic for a VLAN that is designated as part of a disjoint network can only travel along an uplink Ethernet port or port channel that is specifically assigned to that VLAN, and is selectively excluded from all other uplink ports and port channels. By default, data traffic in Cisco UCS works on a principle of mutual inclusion. All traffic for all VLANs and upstream networks travels along all uplink ports and port channels.

Disjoint Layer-2 features:

  • Non-symmetric VLANs on uplink
  • Multiple Layer 2 networks upstream
  • Native support in End-Host mode allows simplification of configuration (no need for Switch mode)
  • By default 1.4 behavior is preserved (all VLANs present in all uplinks)
  • Hardware independent feature (supported in 6100 and 6200 FI)
  • Max of 31 disjointed Layer 2 domains supported
  • Overlapping VLAns are not supported
  • Per VLAN broadcast/multicast listener


System must be running UCS 2.x version. User should have knowledge of basic UCS configuration.

Related Information

Configuring Upstream Disjoint Layer-2 Networks


Hi Robert,


I think I understand the concept, but:


1. what happens to "vlan 1" ?

2. I know that vlan-1 is mapped to both uplinks (if I check with "show int po-x trunk"), but what uplink gets elected to process broadcasts ?


In a specific case I need to segregate some traffic between to different domains but in one of this domains I still have servers in vlan-1 and I can't change their vlan-id for now .... but I need to understand how BUM is processed in vlan-1 for a scenario like this using L2-Disjoint


Best regards,

Bruno Fernandes

Content for Community-Ad