Users Guide

1124 Link Aggregation
Alternative Recommended Layer-3 Connectivity
The loop-free topology shown in Figure 28-13 uses the MLAG switches as
Layer-2 switches in an EOR role. The single VLAN traverses the MLAG
topology from the top router to the bottom storage and servers. Multiple
VLANs in different VPCs may be used to isolate clusters of storage/servers
from each other. This topology is highly recommended, as it utilizes MLAG in
the scenario for which it was intended (redundant full-bandwidth
replacement for spanning tree in a fully Layer-2 topology) and allows the
MLAG peers to detect failures and unblock the appropriate VLANs on the
peer link so that traffic flow can continue unimpeded.
The lower pair of switches connects clusters of storage and servers in a TOR
role in support of devices that do not support link aggregation. Switching
between the storage and the servers within the rack proceeds in the normal
manner and remains isolated on the lower switch pair that is not part of the
MLAG domain. Traffic entering or exiting the rack proceeds over the EOR
MLAG.
Figure 28-13. Alternative Recommended Layer-3 Connectivity
MLAGPeerSwitchMLAGPeerSwitch
MLAG
Router
MLAG
MLAG
Switch(notpartof
MLAGdomain)
Switch(notpartof
MLAGdomain)
Storage
Server
Storage
Server