Users Guide

Version Description
9.10(0.0) Introduced on the S6100–ON.
9.8(2.0) Introduced on the S3100 series.
9.8(1.0) Introduced on the Z9100–ON.
9.8(0.0P5) Introduced on the S4048-ON.
9.8(0.0P2) Introduced on the S3048-ON.
9.7(0.0) Introduced on the S6000-ON.
9.5(0.1) Introduced on the Z9500.
9.2(0.0) Introduced on the M I/O Aggregator. This command is supported in Programmable-
Mux (PMUX) mode only.
9.0.2.0 Introduced on the S6000.
9.0.0.0 Introduced on the Z9000.
8.3.19.0 Introduced on the S4820T.
8.3.12.0 Added port-channel parameter on the S4810.
8.3.8.0 Introduced on the S4810.
Usage
Information
LACP on the VLT ports (on a VLT switch or access device), which are members of the VLT, are not
brought up until the VLT domain is recognized on the access device.
During boot-up in a stacking configuration, the system must be able to reach the DHCP server with the
boot image and configuration image. To receive an offer on static LAGs between switches, only untagged
DHCP requests are sent to the DHCP server. Configure the DHCP server to start in BMP mode.
If the switches are connected using LACP port-channels (for example, the VLT peer and top of rack
[ToR]), use the port-channel option on the ToR-side configuration to allow member ports of an
ungrouped LACP port-channel to inherit VLAN membership of that port channel. This ensures untagged
VLT peer device packets reach the DHCP server on the ToR.
To ungroup the VLT and port-channel configurations, use the no lacp ungroup member
independent command on a VLT port channel.
If you reboot both VLT peers in BMP mode with static VLT LAGs, the DHCP server reply to the DHCP
discover offer may not be forwarded by the ToR to the correct node. To avoid this issue, configure the
VLT LAGs to the ToR and the ToR port channel to the VLT peers with LACP.
If supported by the ToR, enable the lacp-ungroup feature on the ToR using the lacp ungroup
member-independent port-channel command.
If the lacp-ungroup feature is not supported on the ToR, reboot the VLT peers one at a time. After
rebooting, verify that VLTi (ICL) is active before attempting DHCP connectivity.
Use the lacp ungroup member-independent command only if the system connects to nodes using
bare metal provisioning (BMP) to upgrade or boot from the network. Otherwise, when the member links
flap, the links become independent switch ports and forward the traffic even before LACP is formed on
that port.
Ensure that you configure all port channels as hybrid ports and as untagged members of a VLAN where
the LACP ungroup option is applicable.
BMP uses untagged dynamic host configuration protocol (DHCP) packets to communicate with the
DHCP server.
To disable this feature on VLT and port channels, use no lacp ungroup member-independent
{vlt | port-channel} command under the configuration mode.
Example
DellEMC(conf)#lacp ungroup member-independent ?
port-channel LACP port-channel members become switchports
vlt All VLT LACP members become
switchports
1648 Virtual Link Trunking (VLT)