Configuring Multi-chassis Link Aggregation
Interaction with Other Features
OmniSwitch AOS Release 7 Network Configuration Guide
June 2013
page 10-21
Interaction with Other Features
This section contains important information about how other OmniSwitch features interact with MCLAG
instances. Refer to the specific chapter for each feature to get more detailed information about how to
configure and use the feature. MCLAG interaction with other features like:
Spanning Tree Protocol
•
Spanning Tree protocol is not allowed on logical (edge) dual-homed MCLAG aggregates or on local
MCLAG aggregates. Spanning Tree must be disabled on the local MCLAG aggregates within each
multi-chassis peer. This is true regardless of the presence of active ports on both peer switches.
•
MCLAG provides an alternative to Spanning Tree while supporting dual-homed connections between
the edge and aggregation. switches.
•
Since Spanning Tree is disabled on MCLAG ports, MCLAG provides a loop detection mechanism to
detect an invalid network topology. This mechanism provides loop detection for any potential loops
that include a set of MCLAG aggregate ports. For more information, see
.
•
By default, only 802.1D (STP), 802.1w (RSTP), and 802.1Q (MSTP) BPDUs are dropped on MCLAG
ports. Enabling PVST+ compatibility (
spantree pvst+ compatibility enable
) is recommended when
connecting MCLAG devices using the PVST+ protocol.
•
Spanning Tree can run on MCLAG chassis peers, even though Spanning Tree is disabled on MC-LAG
ports. In this case,
>
One of the MCLAG chassis peers should be the Root Bridge of the Spanning Tree domain so that
the VFL is always in the forwarding mode.
>
If 1x1 Spanning Tree is configured, the Root Bridge and backup Root Bridge should be set on
multi-chassis switches for all VLANs.
>
If Flat Spanning Tree mode is used, then set Root Bridge of VLAN 1 on Multi-Chassis ID 1 and
backup Root Bridge on ID 2 switch, vice versa.
>
For MSTP, set the Root Bridge and backup Root Bridge for each MSTP instance on Multi-Chassis
ID 1 and backup Root Bridge on ID 2.
Ethernet Ring Protection
Ethernet Ring Protection (ERP) is not configurable on MCLAG aggregates. ERP can be configured on the
virtual fabric link so that ERP packets can flow on this link. MCLAG prevents VFL from going to a
blocking state on either side of the link regardless of the network topology when the VFL is part of the
ERP ring. In this case, if the VFL is never blocked due to ERP convergence, a trap is generated and switch
log is recorded and informed.
Link Aggregation
•
MCLAG ports configured as dual-homed MCLAG do not support standby ports.
•
Static or dynamic link aggregates are used to create the MCLAG aggregates between an edge device
and the two multi-chassis peer switches.
•
Specific static and dynamic link aggregate configuration and
show
command outputs include parame-
ters to configure MCLAG functionality on the aggregate or display MCLAG aggregate information.