Cisco Nexus 7000 Series Configuration Manual page 28

Guidelines and Limitations for VXLAN
• For multicast, the VPC node that receives the (S, G) join from the RP (rendezvous point) becomes the
DF (designated forwarder). On the DF node, encap routes are installed for multicast.
Decap routes are installed based on the election of a decapper from between the VPC primary node and
the VPC secondary node. The winner of the decap election is the node with the least cost to the RP or
the source. However, if the cost to the RP is the same for both nodes, the VPC primary node is elected.
The winner of the decap election has the decap mroute installed. The other node does not have a decap
route installed.
• On a VPC device, BUM traffic (broadcast, unknown-unicast, and multicast traffic) from hosts is replicated
on the vPC peer-link. A copy is made of every native packet and each native packet is sent across the
vPC peer-link to service orphan-ports connected to the peer VPC switch.
To prevent traffic loops in VXLAN networks, native packets ingressing the vPC peer-link cannot be
sent to an uplink. However, if the peer switch is the encapper, the copied packet traverses the vPC
peer-link and is sent to the uplink.
In a VXLAN vPC deployment with peer switch, encapsulation profile, and bridge domain configurations,
the vPC secondary peer switch does not generate or process BPDUs for bridge domains.
• When vPC peer-link is shut, the loopback primary address is used as the source IP address for
encapsulation by both vPC switches.
Note
• When vPC peer-link is no-shut, the NVE loopback secondary address is used.
• For VPC, the loopback interface has 2 IP addresses: the primary IP address and the secondary IP address.
The primary IP address is unique and is used by Layer 3 protocols.
The secondary IP address on loopback is necessary because the interface NVE uses it for the VTEP IP
address. The secondary IP address must be same on both vPC peers.
• The VPC peer-gateway feature must be enabled on both peers.
As a best practice, use peer-switch, peer gateway, ip arp sync, ipv6 nd sync configurations for improved
convergence in VPC topologies.
The following is an example (best practice) of a VPC configuration:
switch# sh ru vpc
version 6.1(2)I3(1)
feature vpc
vpc domain 2
peer-switch
peer-keepalive destination 172.29.206.65 source 172.29.206.64
peer-gateway
ipv6 nd synchronize
Cisco Nexus 7000 Series NX-OS VXLAN Configuration Guide
20
◦ Using different primary IP addresses.
◦ Consistent NVE interface to VNI mapping.
◦ Consistent VNI to group mapping.
Orphans connected to the VPC secondary will experience loss of traffic for the period
that the vPC peer-link is shut. This is similar to Layer 2 orphans in a VPC secondary of
a traditional VPC setup.
Configuring VXLAN Flood and Learn