Cisco Nexus 6000 Series Configuration Manual page 32

About VLAN Translation
• The number of supported VLAN translation maps is 4000. Layer 2 ports that have the same VLAN maps
and the same trunk allowed VLAN list can benefit from sharing translation entries in hardware.
• For VLAN translation on a FEX, the VLAN translation maps are applicable to all FEX host interfaces
and must be applied to all the FEX fabric or network interfaces. In addition, the translated VLANs
specified in the FEX VLAN translation maps must be individually applied to the trunk allowed VLAN
list of each of the FEX HIF interfaces. All the FEX interfaces must be configured as Layer 2 trunks.
• VLAN translation is not configurable on FEX HIF ports.
• The VLAN translation feature is only applicable to trunk ports. Hence, in the case of a FEX, all FEX
HIF ports must be in trunk mode. When VLAN translation is first enabled on a FEX, a syslog is issued
stating that all FEX HIF ports must be in trunk mode.
• For VLAN translation with vPC, the VLAN translation configuration on vPC primary and secondary
interfaces must be consistent, otherwise the vPC interface on vPC secondary is brought down.
• If VLAN translation is enabled on a port channel, the configuration is applied to all member ports in the
port channel bundle.
• SPAN is supported on trunk ports with VLAN translation enabled.
• PVLAN mode behavior cannot be overlaid on top of ports with VLAN translation enabled.
• To enable DHCP snooping on a port on which VLAN translation is enable, the translated/mapped local
VLAN must be used.
• Do not configure VLAN translation on a Peer-Link.
• Do not use VLAN translation on FabricPath core ports.
• Global VLAN translation is not supported.
• To enable IGMP snooping on a VLAN, the VLAN interface must be capable of multicast routing. If
VLAN translation is enabled on a port, IGMP snooping has to be enabled on the translated VLAN, that
is the local VLAN.
• The following should be taken into consideration when spanning tree (STP) mode is enabled:
Figure 3: VLAN Mapping with SSTP
Cisco Nexus 6000 Series NX-OS Layer 2 Switching Configuration Guide, Release 7.x
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◦ SW1 and SW2 are connected using trunk T that carries VLAN 101. On SW2, per port VLAN
mapping is enabled on trunk port P and one of the mappings is 101 to 202. In the previous diagram,
on the wire BPDU from SW1 has .1q VLAN and TLV VLAN as 101. When this BPDU reaches
port P , its dot1q VLAN is changed from 101 to 202 per the VLAN mapping on Port P. However,
the BPDU TLV VLAN remains 101. When it reaches the spanning tree process, spanning tree
concludes that VLAN 101's BPDU is received on VLAN 202 and spanning tree reports this as an
inconsistent port. To correct the problem, spanning tree should process this BPDU in VLAN 202
and the TLV VLAN should be mapped to translate VLAN and check for consistency. Spanning
tree instance 101 of SW1 is merged with spanning tree instance 202 of SW2. The same process is
Configuring VLANs