MCLAG Overview Configuring Multi-chassis Link Aggregation
page 10-10 OmniSwitch AOS Release 7 Network Configuration Guide June 2013
Edge Switches are any L2 standards-based device, such as a switch or server, that provides network
access to client equipment, such as PCs, servers, and printers. These devices dual home (active/active) into
MCLAG groups aggregated across a pair of OmniSwitch multi-chassis peers.
Multi-Chassis Peer Switches are switches that terminate the aggregate links coming from multiple edge
devices. This implementation supports two peer switches per multi-chassis domain (group).
• Each peer switch can be a member of only one multi-chassis group and must be assigned a unique
chassis ID. MCLAG functionality will remain operationally down if duplicate chassis IDs are detected.
• Each peer switch in a multi-chassis group must be assigned the same group ID number. The group ID
number uniquely identifies a pair of switches operating in the multi-chassis mode. MCLAG functional-
ity will remain operationally down if the same group ID is not used on each switch within the group.
• One of the two peer switches within the domain serves as the primary switch (the switch with the
lowest chassis ID). The role of the switch is automatically determined and only effective when both
switches are up and MCLAG is operational.
• The system MAC address of the primary switch is used throughout the MCLAG domain to create the
LAG Group ID.
Multi-Chassis Link Aggregate is an aggregate of multiple switch ports in which subsets of the ports are
connected to a pair of aggregation switches. This type of aggregate is used to form a dual-homed (active/
active) connection between edge devices and the peer switches.
Virtual Fabric Link (VFL) is an aggregated group of 10G ports that connects the multi-chassis peer
switches. As one of the basic building blocks of a MCLAG configuration, the VFL facilitates the flow of
traffic and the transfer of control data between the multi-chassis peer switches.
IPC VLAN is a special type of VLAN reserved for the inter-chassis communication exchange between
multi-chassis peers. Only VFL ports are assigned to this VLAN, and no other ports are allowed to join the
IPC VLAN.
Virtual IP (VIP) VLAN is a special type of VLAN used to provide the underlying LAN infrastructure for
the support of basic IP/Layer 3 services on a multi-chassis link aggregation group. MCLAG basically
extends L2 aggregated groups across multiple switches. Each multi-chassis peer needs to identify MCLAG
VLANs from non-MCLAG VLANs to manage multi-chassis operations for respective applications,
including IP interfaces and services.
VIP VLAN IP Interface is an IP interface configured for a VIP VLAN that consists of two IP addresses:
a virtual IP address that is the same on each peer switch and a local IP address to provide management
access to a specific switch. Configuring a VIP VLAN IP interface is the recommended way to access an
MCLAG configuration over a routed network. This implementation of a VIP interface:
• Provides a common IP address for both multi-chassis peer switches.
• Synchronizes the ARP information between the two peer switches, allowing either one of the peer
switches to respond to ARP requests coming from the MCLAG aggregates.
• Serves as the default gateway for devices attached to the respective subnet.
• Cannot be bound to any routing protocol or establish any routing adjacencies.
• Routes only locally between MCLAG subnets. By configuring route maps, VIP subnets can converge
with external routes.
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