HP Cisco Nexus 5000 Cisco Nexus 5000 Series Switch CLI Software Configuration - Page 179

vPC Number, vPC Interactions with Other Features, vPC and LACP, vPC Peer Links and STP

Page 179 highlights

Information About vPCs vPC Number • We recommend that you configure Unidirectional Link Detection (UDLD) on both sides of the vPC peer link. vPC Number Once you have created the vPC domain ID and the vPC peer link, you can create EtherChannels to attach the downstream switch to each vPC peer switch. That is, you create one EtherChannel from the downstream switch to the primary vPC peer switch and you create another EtherChannel from the downstream switch to the secondary peer switch. On each vPC peer switch, you assign the same vPC number to the EtherChannel that connects to the downstream switch. You will experience minimal traffic disruption when you are creating vPCs. To simplify the configuration, you can assign the vPC ID number for each EtherChannel to be the same as the EtherChannel itself (that is, vPC ID 10 for EtherChannel 10). Note The vPC number that you assign to the EtherChannel connecting to the downstream switch from the vPC peer switch must be identical on both vPC peer switches. vPC Interactions with Other Features vPC and LACP The Link Aggregation Control Protocol (LACP) uses the system MAC address of the vPC domain to form the LACP Aggregation Group (LAG) ID for the vPC. You can use LACP on all the vPC EtherChannels, including those channels from the downstream switch. We recommend that you configure LACP with active mode on the interfaces on each EtherChannel on the vPC peer switches. This configuration allows you to more easily detect compatibility between switches, unidirectional links, and multihop connections, and provides dynamic reaction to run-time changes and link failures. The vPC peer link supports 16 EtherChannel LACP interfaces. You should manually configure the system priority on the vPC peer-link switches to ensure that the vPC peer-link switches have a higher LACP priority than the downstream connected switches. A lower numerical value system priority means a higher LACP priority. Note When manually configuring the system priority, you must ensure that you assign the same priority value on both vPC peer switches. If the vPC peer switches have different system priority values, vPC will not come up. vPC Peer Links and STP When you first bring up the vPC functionality, 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. OL-16597-01 Cisco Nexus 5000 Series Switch CLI Software Configuration Guide 133

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• We recommend that you configure Unidirectional Link Detection (UDLD) on both sides of the vPC
peer link.
vPC Number
Once you have created the vPC domain ID and the vPC peer link, you can create EtherChannels to attach the
downstream switch to each vPC peer switch. That is, you create one EtherChannel from the downstream
switch to the primary vPC peer switch and you create another EtherChannel from the downstream switch to
the secondary peer switch.
On each vPC peer switch, you assign the same vPC number to the EtherChannel that connects to the downstream
switch. You will experience minimal traffic disruption when you are creating vPCs. To simplify the
configuration, you can assign the vPC ID number for each EtherChannel to be the same as the EtherChannel
itself (that is, vPC ID 10 for EtherChannel 10).
The vPC number that you assign to the EtherChannel connecting to the downstream switch from the vPC
peer switch must be identical on both vPC peer switches.
Note
vPC Interactions with Other Features
vPC and LACP
The Link Aggregation Control Protocol (LACP) uses the system MAC address of the vPC domain to form
the LACP Aggregation Group (LAG) ID for the vPC.
You can use LACP on all the vPC EtherChannels, including those channels from the downstream switch. We
recommend that you configure LACP with active mode on the interfaces on each EtherChannel on the vPC
peer switches. This configuration allows you to more easily detect compatibility between switches, unidirectional
links, and multihop connections, and provides dynamic reaction to run-time changes and link failures.
The vPC peer link supports 16 EtherChannel LACP interfaces. You should manually configure the system
priority on the vPC peer-link switches to ensure that the vPC peer-link switches have a higher LACP priority
than the downstream connected switches. 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
on both vPC peer switches. If the vPC peer switches have different system priority values, vPC will not
come up.
Note
vPC Peer Links and STP
When you first bring up the vPC functionality, 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.
Cisco Nexus 5000 Series Switch CLI Software Configuration Guide
OL-16597-01
133
Information About vPCs
vPC Number