Cfsoe; Vpc Peer Switch - Cisco Nexus 3548 Configuration Manual

CFSoE

STP is distributed; that is, the protocol continues running on both vPC peer switches. However, the configuration
on the vPC peer switch elected as the primary switch controls the STP process for the vPC interfaces on the
secondary vPC peer switch.
The primary vPC switch synchronizes the STP state on the vPC secondary peer switch using Cisco Fabric
Services over Ethernet (CFSoE).
The vPC manager performs a proposal/handshake agreement between the vPC peer switches that sets the
primary and secondary switches and coordinates the two switches for STP. The primary vPC peer switch then
controls the STP protocol for vPC interfaces on both the primary and secondary switches.
The Bridge Protocol Data Units (BPDUs) use the MAC address set for the vPC for the STP bridge ID in the
designated bridge ID field. The vPC primary switch sends these BPDUs on the vPC interfaces.
Note Display the configuration on both sides of the vPC peer link to ensure that the settings are identical. Use the
show spanning-tree command to display information about the vPC.
CFSoE
The Cisco Fabric Services over Ethernet (CFSoE) is a reliable state transport mechanism that you can use to
synchronize the actions of the vPC peer devices. CFSoE carries messages and packets for many features linked
with vPC, such as STP and IGMP. Information is carried in CFS/CFSoE protocol data units (PDUs).
When you enable the vPC feature, the device automatically enables CFSoE, and you do not have to configure
anything. CFSoE distributions for vPCs do not need the capabilities to distribute over IP or the CFS regions.
You do not need to configure anything for the CFSoE feature to work correctly on vPCs.
You can use the show mac address-table command to display the MAC addresses that CFSoE synchronizes
for the vPC peer link.
Note
Do not enter the no cfs eth distribute or the no cfs distribute command. CFSoE must be enabled for vPC
functionality. If you do enter either of these commands when vPC is enabled, the system displays an error
message.
When you enter the show cfs application command, the output displays "Physical-eth," which shows the
applications that are using CFSoE.

vPC Peer Switch

The vPC peer switch feature was added to address performance concerns around STP convergence. This
feature allows a pair of Cisco Nexus 3500 Series switches to appear as a single STP root in the Layer 2
topology. This eliminates the need to pin the STP root to the vPC primary switch and improves vPC convergence
if the vPC primary switch fails.
To avoid loops, the vPC peer link is excluded from the STP computation. In vPC peer switch mode, STP
BPDUs are sent from both vPC peer devices to avoid issues related to STP BPDU timeout on the downstream
switches, which can cause traffic disruption.
vPC peer switch can be used with the pure peer switch topology in which the devices all belong to the vPC.
Cisco Nexus 3548 Switch NX-OS Interfaces Configuration Guide, Release 9x
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Configuring Virtual Port Channels