Network Considerations For Vxlan Deployments - Cisco Nexus 7000 Series Configuration Manual

Configuring VXLAN Flood and Learn
• On a VPC pair, shutting down NVE or NVE loopback on one of the VPC nodes is not a supported
configuration. This means that traffic fail over on one-side NVE shut or one-side loopback shut is not
supported.
• Redundant anycast RPs configured in the network for multicast load-balancing and RP redundancy are
supported on VPC VTEP topologies.
• The following are the examples of SVI with PIM enabled:
switch# show run interface BDI3
interface BDI3
switch# show run interface BDI3
interface BDI3
description special_svi_over_vPC peer-link no shutdown
ipv6 address FE80::290:27FF:FE8C:B709
ip pim sparse-mode
Note
• As a best practice when changing the secondary IP address of an anycast VPC VTEP, the NVE interfaces
on both the VPC primary and the VPC secondary should be shut before the IP changes are made.
• For a VXLAN vPC deployment, you should configure the switchport trunk native vlan tag exclude
control command on the interface port channel configured as the vPC peer-link.

Network Considerations for VXLAN Deployments

• MTU Size in the Transport Network
Due to the MAC-to-UDP encapsulation, VXLAN introduces 50-byte overhead to the original frames.
Therefore, the maximum transmission unit (MTU) in the transport network needs to be increased by 50
bytes. If the overlays use a 1500-byte MTU, the transport network needs to be configured to accommodate
1550-byte packets at a minimum. Jumbo-frame support in the transport network is required if the overlay
applications tend to use larger frame sizes than 1500 bytes.
• ECMP and LACP Hashing Algorithms in the Transport Network
As described in a previous section, Cisco Nexus 7000 Series Switches introduce a level of entropy in
the source UDP port for ECMP and LACP hashing in the transport network. As a way to augment this
implementation, the transport network uses an ECMP or LACP hashing algorithm that takes the UDP
source port as an input for hashing, which achieves the best load-sharing results for VXLAN encapsulated
traffic.
• Multicast Group Scaling
The VXLAN implementation on Cisco Nexus 7000 Series Switches uses multicast tunnels for broadcast,
unknown unicast, and multicast traffic forwarding. Ideally, one VXLAN segment mapping to one IP
ip arp synchronize
description special_svi_over_mct
no shutdown
ip address 30.2.1.1/30
ip pim sparse-mode
The SVI must be configured on both VPC peers and requires PIM to be enabled.
Guidelines and Limitations for VXLAN
Cisco Nexus 7000 Series NX-OS VXLAN Configuration Guide
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