- * For cisco VIC vNIC, set default to VLAN strip enabled, unless
- * specified otherwise in the startup config.
- * For other NICs default to VLAN strip disabled, unless specified
+ * A note on Cisco VIC (PMD_ENIC) and VLAN:
+ *
+ * With Cisco VIC vNIC, every ingress packet is tagged. On a
+ * trunk vNIC (C series "standalone" server), packets on no VLAN
+ * are tagged with vlan 0. On an access vNIC (standalone or B
+ * series "blade" server), packets on the default/native VLAN
+ * are tagged with that vNIC's VLAN. VPP expects these packets
+ * to be untagged, and previously enabled VLAN strip on VIC by
+ * default. But it also broke vlan sub-interfaces.
+ *
+ * The VIC adapter has "untag default vlan" ingress VLAN rewrite
+ * mode, which removes tags from these packets. VPP now includes
+ * a local patch for the enic driver to use this untag mode, so
+ * enabling vlan stripping is no longer needed. In future, the
+ * driver + dpdk will have an API to set the mode after
+ * rte_eal_init. Then, this note and local patch will be
+ * removed.
+ */
+
+ /*
+ * VLAN stripping: default to VLAN strip disabled, unless specified