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Cisco ACI - VLAN Types


Unlike the traditional Cisco switching world, where there existed only 3 VLAN types (standard, extended, private), Cisco ACI is definitely supposed to have several of them, to ensure that multitudes of Network Professionals get their brains wired!


Luckily, I came across the following ones which seem to make sense about their respective roles to have the traffic forwarding in place:


  1. VLAN ID (VlanID) - Platform independent VLAN that is locally significant to each switch. This VLAN is automatically bound to the port-group VLAN existing on the DVS. It is derived from the VLAN pool that is configured in the Fabric Access Policies.
  2. Hardware VLAN ID (HW_VlanId) - In order to switch traffic locally, most leaf switches comprise of Broadcom ASIC. This VLAN type is utilized by the Broadcom ASIC chip.
  3. Connect to Broadcom ASIC on the leaf : vsh_lc
  4. To generate the list of endpoints connected : show system internal eltmc info vlan brief

The various VLAN types are:


  • BD_CTRL_VLAN - Infrastructure VLANs.
  • BD_EXT_VLAN - These are External VLANs (eg. External Layer 3 Out).
  • FD_VLAN - These VLANs are used for EPGs. It is usually mapped to a specific EPG. On this VLAN, direct learning of endpoints from Hosts occurs.
  • BD_VLAN - Known as Bridge Domain VLAN, it can map to a single or multiple encap (FD) VLANs and VXLANs. On this VLAN no direct learning occurs.

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