Vlags Versus Port Lags - Lenovo ThinkSystem NE2552E Application Manual

VLAGs versus Port LAGs

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Though similar to regular port LAGs in many regards, VLAGs differ from regular
port LAGs in a number of important ways:
 A VLAG can consist of multiple ports on two VLAG peers, which are connected
to one logical client device such as a server, switch or another VLAG device.
 The participating ports on the client device are configured as a regular port
LAG.
 The VLAG peers must be the same model and run the same software version.
 VLAG peers require a dedicated inter‐switch link (ISL) for synchronization. The
ports used to create the ISL must have the following properties:
ISL ports must have VLAN tagging turned on.

ISL ports must be configured for all VLAG VLANs.

ISL ports must be placed into a regular port LAG (dynamic or static).

A minimum of two ports on each switch are recommended for ISL use.

Dynamic routing protocols, such as OSPF, cannot terminate on VLAGs.

 Routing over VLAGs is not supported. However, IP forwarding between
subnets served by VLAGs can be accomplished using VRRP.
 VLAGs are configured using additional commands.
 It is recommended that end‐devices connected to VLAG switches use NICs with
dual‐homing. This increases traffic efficiency, reduces ISL load and provides
faster link failover.
Chapter 11: Virtual Link Aggregation Groups
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