51VLAN StackingWith the virtual local area network (VLAN)-stacking feature (also called stackable VLANs and QinQ), you can “stack”VLANs into one tunnel and switch them through the network transparently.This feature is supported by the Dell Force10 operating software (FTOS) on the C-Series, E-Series, S-Series, Z-Series, orS4810 platforms.For more information about basic VLAN commands, refer to theVirtual LAN (VLAN) Commands section in the Layer 2chapter.Important Points to Remember• If you do not enable the spanning tree protocol (STP) across the stackable VLAN network, STP bridge protocoldata units (BPDUs) from the customer’s networks are tunneled across the stackable VLAN network.• If you do enable STP across the stackable VLAN network, STP BPDUs from the customer’s networks areconsumed and not tunneled across the stackable VLAN network unless you enable protocol tunneling.NOTE: For more information about protocol tunneling on the E-Series, refer to Service Provider Bridging.• Layer 3 protocols are not supported on a stackable VLAN network.• Assigning an IP address to a stackable VLAN is supported when all the members are only stackable VLAN trunkports. IP addresses on a stackable VLAN-enabled VLAN is not supported if the VLAN contains stackable VLANaccess ports. This facility is provided for the simple network management protocol (SNMP) management over astackable VLAN-enabled VLAN containing only stackable VLAN trunk interfaces. Layer 3 routing protocols onsuch a VLAN are not supported.• Dell Force10 recommends that you do not use the same MAC address, on different customer VLANs, on thesame stackable VLAN.• Interfaces configured using stackable VLAN access or stackable VLAN trunk commands are not switch trafficfor the default VLAN. These interfaces are switch traffic only when they are added to a non-default VLAN.• Starting with FTOS version 7.8.1 for C-Series and S-Series (FTOS version 7.7.1 for E-Series, 8.2.1.0 for E-SeriesExaScale), a vlan-stack trunk port is also allowed to be configured as a tagged port and as an untagged port forsingle-tagged VLANs. When the vlan-stack trunk port is also a member of an untagged vlan, the port must be inHybrid mode. Refer to portmode hybrid.dei enableMake packets eligible for dropping based on their DEI value.C-Series, S-Series, S4810Syntax dei enableDefaults Packets are colored green; no packets are dropped.1445
