Configuring the VXLAN Underlay Network

Configuring the underlay network involves the configuration of (at least) the following base features:

  • Layer 2
  • Layer 3
  • The fabric
  • Clustering
  • vLAGs
  • Optionally (even though it’s highly recommended), traffic analytics

Readers are referred to the respective configuration sections of each feature for more details.

In addition, on Arista switches jumbo frame support can be enabled on the appropriate interfaces to accept frames with an MTU larger than 1500 bytes (namely, with a ‘jumbo’ size). Refer to the Enabling Jumbo Frame Support section earlier in this guide for details.

This guarantees that all standard maximum size packets to be transmitted in the overlay network are not dropped by the underlay.

Moreover, starting from release 2.5.0, NetVisor OS enforces a routing MTU size in hardware, which can be set with the mtu option when adding vRouter interfaces (see examples below).

Therefore, in order to avoid large frames to be dropped during Layer 3 forwarding or during encapsulation, in addition to enabling jumbo frames on physical interfaces, it is also important to configure routed interfaces with the proper MTU settings (typically between 1580 and 9398 bytes).

Changes to interface attributes (such as the MTU) are recommended to be applied in the initial phases of the underlay configuration. Moreover, changing the MTU on certain higher-level entities such as trunk ports may require more specific commands (such as trunk-modify instead of the basic port-config-modify command).