Guidelines And Limitations For Configuring Vlans - Cisco Nexus 6000 Series Configuration Manual

Configuring VLANs
machines in the first datacenter, the core Cisco Nexus device in the second datacenter must translate the VLAN
ID in the ingress packets on the trunk port from the ingress VLAN 100 to the local VLAN 101. The local
VLAN tag is a function of the port on which the traffic arrives and the ingress VLAN tag on which it arrives.
Upon egress from the trunk port, the reverse translation must be to convert VLAN 101 to VLAN 100.
For example, VLAN translation can be enabled on a port such that packets with ingress VLANs V1,V2...V10
are mapped to local VLANs V101, V102,...,V110, the packets coming in to the second network are tagged
as follows:
V1, V2, V10 map to V101, V102, V110 respectively (Packets are single tagged and tag is a function of ingress
VLAN tag and port).
For a given port, there is a strict one-to-one mapping of the ingress VLAN to local VLAN and more than one
ingress VLAN is not allowed to map to the same local VLAN.

Guidelines and Limitations for Configuring VLANs

VLANs have the following configuration guidelines and limitations:
• The maximum number of VLANs per VDC is 4094.
• You can configure a single VLAN or a range of VLANs.
When you configure a large number of VLANs, first create the VLANs using the vlan command (for
example, vlan 200 to 300, 303 to 500). After the VLANs have been successfully created, name or
configure those VLANs sequentially.
• VLAN 4094 is a reserved VLAN.
• You cannot create, modify, or delete any VLANs that are within the group of VLANs reserved for
internal use.
• VLAN1 is the default VLAN. You cannot create, modify, or delete this VLAN.
• VLANs 1006 to 4094 are always in the active state and are always enabled. You cannot suspend the
state or shut down these VLANs.
VLAN translation has the following guidelines and limitations:
• A VLAN translation configuration is only applicable to Layer 2 trunks. It is inactive when applied to
ports that are not Layer 2 trunks.
• Do not configure translation of ingress native VLAN traffic on an 802.1Q trunk. The 802.1Q native
VLAN traffic is untagged and cannot be recognized for translation. However, you can translate traffic
from other VLANs to the native VLAN of an 802.1Q trunk.
• The VLANs to which you are translating must be present in the trunk's allowed VLAN list. In addition,
the VLANs that need to be forwarded on a trunk port, that are not involved in VLAN translation must
also be included in the trunk ports allowed VLAN list. With per-port VLAN translation enabled, VLAN
translation entries are consumed in hardware for all VLANs in the trunk ports allowed VLAN list.
• Do not change the VLAN on an access port or a trunk port it will flap the interface. However, if the port
is part of a vPC, then first change the native VLAN on the secondary vPC, and then on the primary vPC.
• A VLAN translation must ensure that the original and translated VLANs are within the same MST
instance.
Cisco Nexus 6000 Series NX-OS Layer 2 Switching Configuration Guide, Release 7.x
About VLAN Translation
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