VXLAN EVPN Troubleshooting: What Actually Breaks
Four faults hit in a real Nexus fabric, the output that identified them, and an ordered method for the next one.
Go Deeper on Enterprise Networking
In-depth tutorials on OSPF, BGP, 802.1X, and more- for engineers who want to understand the why, not just the how.
OSPF
Open Shortest Path First, the link-state IGP behind most enterprise networks. Articles tagged OSPF cover neighbor relationships, LSA types, areas, DR/BDR election, and Cisco IOS XE configuration.
61 posts
BGP
Border Gateway Protocol, the path-vector protocol that holds the internet together and increasingly runs inside enterprise data centers. Articles tagged BGP cover fundamentals, neighbor states, path attributes, best-path selection, traffic engineering, and Cisco IOS XE configuration.
60 posts
802.1X
Port-based network access control, the standard for authenticating users and devices onto wired and wireless networks. Articles tagged 802.1X cover supplicant and authenticator behavior, RADIUS, EAP methods, Cisco ISE, dynamic VLANs, dACLs, host modes, and phased deployment.
38 posts
VLAN
Virtual LANs and Layer 2 switching, the foundation of every campus network. Articles tagged VLAN cover fundamentals, trunking, inter-VLAN routing, EtherChannel, troubleshooting, and campus design on Cisco Catalyst switches.
47 posts
Wireless
Enterprise Wi-Fi on Cisco Catalyst 9800, the WLC platform that replaced the AireOS generation. Articles tagged Wireless cover the configuration model, AP join, WPA3, FlexConnect, RRM, fast roaming, SSO HA, and IOS XE troubleshooting.
52 posts
STP
Spanning Tree Protocol, the loop-prevention mechanism that keeps Layer 2 networks stable. Articles tagged STP cover port roles and states, RSTP and MST, root bridge configuration, BPDU Guard and Root Guard hardening, and Cisco Catalyst troubleshooting.
36 posts
Latest posts
EVPN L3VNI and the Distributed Anycast Gateway
Symmetric IRB routes between VNIs on the leaf that receives the packet. Here is the L3VNI build and the real output that proves it worked.
A Real VXLAN Packet, Header by Header
A genuine VXLAN packet captured between a spine and a leaf, taken apart byte by byte from the outer MAC down to the ICMP echo request inside.
VXLAN L2VNI Configuration on Nexus, Proven
An L2VNI build on a real Nexus fabric, including the vPC anycast VTEP mistake that produced an empty peer table and how it was fixed.
BGP EVPN Route Types Explained with Real Output
EVPN route types stop being abstract the moment you read them off a real fabric. Here are Types 2, 3 and 5 from a working Nexus lab.
Ingress Replication vs PIM Anycast RP in VXLAN
BUM traffic still has to get everywhere in a VXLAN fabric. Here is how ingress replication handles it, and what you give up by not running PIM.
Spine-Leaf Underlay with OSPF on Nexus
A spine-leaf underlay should be the least interesting part of your fabric. Here is the OSPF build that gets you there, with real Nexus output.
vPC Failure Modes: Peer-Link, Keepalive, Type-1
The vPC failure matrix, with the Type-1 mismatch demonstrated on real hardware and the peer-link and keepalive rows explained rather than faked.
vPC Explained: Build It and Read Its Health
A real NX-OS vPC build with the warnings it emits, the health output decoded field by field, and an honest look at orphan ports.
Nexus Port-Channels and LACP: Suspended Members
Why NX-OS rejects channel-group before feature lacp, how to read the port-channel flags legend, and what a suspended member actually means.
NX-OS Fundamentals: Your First Thirty Minutes on a Nexus
A practical orientation for your first console session on a Cisco Nexus: what the box is, what is turned on, which VRF you are in, and how to save it properly.
NX-OS vs IOS XE: What Changes on Your First Nexus
If you know IOS XE cold, most of NX-OS will feel familiar until it suddenly does not. Here are the six differences that bite on day one, with real Nexus 9000v output.