Cisco 7206 - VXR Router Configuration Manual page 223

Chapter 7 Configuring vPCs
S e n d d o c u m e n t c o m m e n t s t o n e x u s 7 k - d o c f e e d b a c k @ c i s c o . c o m
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vPC and LACP
LACP uses the system MAC address of the vPC domain to form the LACP Aggregation Group (LAG) ID
for the vPC. (See
You can use LACP on all the vPC port channels, including those channels from the downstream device.
We recommend that you configure LACP with active mode on the interfaces on each port channel on the
vPC peer devices. This configuration allows you to more easily detect compatibility between devices,
unidirectional links, and multihop connection, and provides dynamic reaction to run-time changes and
link failures.
With M- series modules and LACP, vPC peer link supports 16 LACP interfaces: 8 active links and 8 hot
standby links. You can configure 16 LACP links on the downstream vPC channel: 8 active links and 8
hot standby links. If you configure the port channels without using LACP, you can have only 8 links in
each channel. With F-Series line-cards, vPC peer link and downstream vPC channels support upto 16
active LACP links. You can have 16 links in each channel even if the port channels are not configured
using LACP.
We recommend that you manually configure the system priority on the vPC peer link devices to ensure
that the vPC peer link devices have a higher LACP priority than the downstream connected devices. A
lower numerical value system priority means a higher LACP priority.
When manually configuring the system priority, you must ensure that you assign the same priority value
Note
on both vPC peer devices. If the vPC peer devices have different system priority values, vPC will not
come up.
vPC Peer Links and STP
Although vPCs provides a loop-free Layer 2 topology, Spanning Tree Protocol (STP) is still required to
provide a "fail-safe" mechanism to protect against any incorrect or defective cabling or possible
misconfiguration. When you first bring up vPC, STP reconverges. STP treats the vPC peer link as a
special link and always includes the vPC peer link in the STP active topology.
We recommend that you set all the vPC peer link interfaces to the STP network port type so that Bridge
Assurance is automatically enabled on all vPC peer links. We also recommend that you do not enable
any of the STP enhancement features on vPC peer links. It will not cause any problems if the STP
enhancements are already configured, but you need not configure these.
When you are running both MST and Rapid PVST+, ensure that the PVST simulation feature is correctly
configured.
See the Cisco Nexus 7000 Series NX-OS Layer 2 Switching Configuration Guide, Release 5.x, for
information on STP enhancement features and PVST simulation.
You must configure a list of parameters to be identical on the vPC peer devices on both sides of the vPC
Note
peer link. See the
about these required matched settings.
OL-23435-03
CFSoE, page 7-26
vPC and Orphan Ports, page 7-27
Chapter 6, "Configuring Port Channels,"
"Compatibility Parameters for vPC Interfaces" section on page 7-15
Cisco Nexus 7000 Series NX-OS Interfaces Configuration Guide, Release 5.x
Information About vPCs
for information on LAG-ID and LACP.)
for information
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