Dell N2000 Series, Configuration Manual

Page: 949 / 1460

Configuring Link Aggregation
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L3 VLAN Termination on MLAG Not Supported
In the “two-armed” fully routed scenario shown in Figure 28-14, both the
routed network and the switched network are in the MLAG. Switched traffic
to and from the upstream network is automatically unblocked over the peer-
link when an MLAG link fails. But, because the failed link is part of an L3
port-channel (with a unique VLAN), the peer-link does not automatically
unblock the downstream routed VLANs (which are not correlated with the
upstream MLAG VLANs) across the peer link. Specifically, MLAG does not
correlate the failure in VLAN 30 with VLAN 20. This leads to a black hole.
Adding a backup routed link solves the black hole issue, but it also makes the
MLAG solution unnecessary. L3-routed VLAN termination on the MLAG
peers is not supported—VLANs must extend across the MLAG peers to two
MLAG partners.
Figure 28-14. L3 VLAN Termination on MLAG, Example 1
MLAG Router Peer MLAG Router Peer
Peer-Link
MLAG
Router
MLAG
VLAN 30
Failed Link
Switched Network
Only
VLAN 20