Arista on Council of Elrond

Cheat_Sheet

Tue, 21 Jul 2026 04:00:00 +0800

Every verification and troubleshooting command from the lab posts on this blog, collected in one place and organized by vendor — because that’s how you reach for a cheat sheet: you’re on a box, and you need to know what to run. Each subsection links back to the post it came from and explains what each command shows and what a healthy result looks like — a command you can’t interpret is just noise.

Arista_VXLAN_EVPN_Lab

Tue, 21 Jul 2026 00:30:00 +0800

A VXLAN fabric has to answer one question before any host can talk: how does BUM traffic (Broadcast, Unknown unicast, Multicast) reach every remote VTEP? There are only two data-plane answers — head-end replication (HER, also called ingress replication) or an IP multicast underlay — and two control-plane ways to drive each of them (static configuration or BGP EVPN).

This lab builds the same Arista fabric four times, once per combination:

Arista_EOS_RoCEv2_Lossless_Config

Mon, 20 Jul 2026 04:00:00 +0800

On Cisco NX-OS, enabling PFC for RoCE normally involves several MQC (Modular QoS CLI class-map -> policy-map -> system qos) layers. On Arista EOS, basic PFC can be enabled directly on an interface with two commands:

priority-flow-control on
priority-flow-control priority 3 no-drop

Those two commands are only the PFC portion of a complete RoCEv2 design. A deployable configuration must also define classification, queue scheduling, ECN, watchdog behavior, buffer thresholds, and the policy on every possible congestion point.