EVPN/VXLAN MTU Troubleshooting: Why Ping Works but Applications Fail

MTU bugs in an EVPN/VXLAN fabric are frustrating because the control plane usually looks healthy. BGP EVPN is established, VNIs are present, MAC/IP routes are learned, and a normal ping may work. Then a backup job, storage mount, database replication stream or RoCEv2 workload starts moving real payloads and traffic becomes intermittent.

The root cause is often simple: one link, port-channel member, routed subinterface, firewall hop, DCI handoff or host interface cannot carry the larger encapsulated frame. This article gives a practical workflow to prove or eliminate MTU as the issue without guessing.

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BGP Unnumbered Leaf-Spine: Practical Design and Troubleshooting Checklist

BGP unnumbered is one of those data-center fabric features that looks almost too simple when it works: no per-link IPv4 addressing, a repeatable interface template, and eBGP sessions built over IPv6 link-local addresses. The operational catch is that the failure mode moves from “is this /31 correct?” to “is neighbor discovery, peer discovery, policy and next-hop resolution all aligned?”

This post is a practical checklist for building and troubleshooting a small leaf-spine fabric with BGP unnumbered. It is vendor-neutral in structure, with sample commands shown as patterns rather than copy-paste production configuration.

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MPLS L3VPN Route Target Troubleshooting: Fix Missing VRF Routes Safely

MPLS L3VPN route-target troubleshooting usually starts with a simple ticket: “the route is not in the VRF”, “site B cannot reach site A”, or “the shared service network disappeared after a change”. The fix is rarely to paste another broad route-target import line. A missing VPN route can be caused by CE routing, VRF export policy, MP-BGP propagation, route-reflector behavior, next-hop reachability, import policy, firewalling, or a missing return path.

This practical checklist shows a safe way to troubleshoot MPLS L3VPN and VRF route leaking without turning a clean segmentation design into an accidental any-to-any network. It is written in vendor-neutral terms, so you can adapt it to IOS-XR, IOS-XE, NX-OS, Junos, SR OS, FRR or a controller-driven environment.

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Weekly BGP Table Watch: IPv4, IPv6 and ASN Changes — 2026-08-17

The global BGP table keeps moving every day. This weekly BGP Table Watch snapshot tracks IPv4 prefixes, IPv6 prefixes, visible ASNs and the largest routing-table changes reported during the last week.

The goal is not to alarm on every change. BGP is noisy by design. The goal is to build a simple operational habit: watch the size of the routing table, notice large origin-AS changes, and keep an eye on where new ASNs and route withdrawals appear.

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Backup Network Segmentation: VLANs, VRFs and Firewall Rules Against Ransomware

Backup network segmentation is one of the cheapest controls that can stop a ransomware incident from becoming a total rebuild. Many small and mid-size environments protect production servers with decent backup software, but then place the backup console, proxies and repository in the same routing domain as users, printers, Wi-Fi clients or general server management. When an attacker gets an admin token or moves laterally, the backup platform becomes just another target.

This article shows a practical, vendor-neutral design for separating backup traffic with VLANs, VRFs and firewall rules. It fits SMB, home lab, branch and small data-center networks, and it complements the Start Here networking topics, Data Center Networking and Resources pages.

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RoCEv2 Troubleshooting Checklist: PFC, ECN and GPU Storage Latency

RoCEv2 troubleshooting is hard because the failure often looks like an application problem: GPU jobs stall, checkpoint writes take longer, a storage node looks slow, or one rack suddenly drags down the rest of the pod. The network may show no classic packet loss on a normal interface graph, while the real issue is hiding in priority queues, ECN marking, PFC pause frames, NIC classification, or a backup flow accidentally sharing the lossless class.

This practical checklist is for small and mid-size AI clusters, data-center labs and private GPU pods where RoCEv2 is used for storage, distributed training or low-latency east-west traffic. It complements the AI Infrastructure hub, the Data Center Networking hub, and the broader Start Here networking topics page.

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Out-of-Band Management Network Design: A Practical Recovery Checklist

Out-of-band management network design is not a luxury reserved for very large data centers. A small colocation rack, AI lab, branch office or secure SMB environment needs a recovery path that still works when the firewall policy is wrong, the EVPN/VXLAN fabric is unstable, a route leak breaks the WAN, or ransomware reaches user subnets.

This article turns the idea into a practical design checklist: what to separate, what to allow, what to monitor, and how to verify that the management network is actually useful during an incident. For related design topics, see Start Here, the Data Center Networking hub, AI Infrastructure, and the Resources page.

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AI Cluster Storage Network Design: Stop Backups from Breaking GPU Jobs

AI cluster storage networking is where many small GPU pods quietly become unreliable. The compute network may look healthy, but training jobs still stall because NFS reads, checkpoint writes, storage rebuilds and backup copies compete in the same queues.

This guide gives a practical design and troubleshooting checklist for RoCEv2, NVMe/TCP, NFS or parallel file system traffic in a modest AI cluster. It is written for engineers building private GPU pods, data center labs or SMB AI infrastructure without a huge observability stack. For adjacent topics, see the AI Infrastructure hub, Data Center Networking, and the Start Here page.

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EVPN/VXLAN Monitoring Checklist: Find Fabric Problems Before Users Do

EVPN/VXLAN monitoring should answer one operational question quickly: is the problem in the transport underlay, the EVPN overlay, or the tenant service? Without that separation, a single application complaint can turn into a long hunt through BGP sessions, NVE state, MAC tables, firewall policy and endpoint behavior.

This practical guide builds a small but useful monitoring checklist for leaf-spine fabrics. It is aimed at network engineers running data center fabrics, AI/GPU pods, lab environments or SMB private clouds where a full commercial observability platform may not be available yet. For related design topics, see the Data Center hub, the AI Infrastructure page and the Start Here networking topics page.

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AI-Assisted Network Change Review: Guardrails for BGP and EVPN/VXLAN Automation

AI-assisted network change review is useful when it behaves like a strict senior engineer: it reads the intended change, asks boring questions, points out risky lines, and produces verification commands. It is dangerous when it becomes an unguarded shortcut that receives raw customer data or is allowed to push configuration without human control.

This practical workflow shows how to add AI guardrails around BGP, EVPN/VXLAN and data center changes while keeping secrets, customer details and approvals outside the model. If you are building a broader automation practice, start with the Start Here networking topics page and the AI Infrastructure hub.

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EVPN/VXLAN Change Validation: Practical Pre-Checks, Post-Checks and Rollback Triggers

EVPN/VXLAN change validation is where many otherwise clean data-center changes succeed or fail. The configuration is rarely the hardest part; the harder part is proving that the underlay, BGP EVPN control plane, VNI mapping, anycast gateway and host reachability all still agree after the change.

This practical workflow is designed for adding a VLAN/VNI, extending a tenant VRF, replacing a leaf, or changing an anycast gateway in a leaf-spine fabric. It is vendor-neutral, with NX-OS-style command examples because that format is familiar to many operators. For broader context, see the Data Center hub and the AI Infrastructure page.

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Weekly BGP Table Watch: IPv4, IPv6 and ASN Changes — 2026-08-10

The global BGP table keeps moving every day. This weekly BGP Table Watch snapshot tracks IPv4 prefixes, IPv6 prefixes, visible ASNs and the largest routing-table changes reported during the last week.

The goal is not to alarm on every change. BGP is noisy by design. The goal is to build a simple operational habit: watch the size of the routing table, notice large origin-AS changes, and keep an eye on where new ASNs and route withdrawals appear.

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BGP Maintenance Drain: Practical Checklist for Zero-Downtime Network Changes

BGP maintenance draining is one of those small operational habits that prevents a planned change from looking like an outage. The idea is simple: before reloading a leaf switch, replacing an optic, moving a firewall uplink, or touching an edge router, make the affected path less attractive, prove traffic has moved, and only then take the disruptive action.

This article shows a practical workflow for data center and service-provider style networks using BGP, EVPN/VXLAN, MPLS VPN or plain Internet edge routing. It is intentionally vendor-neutral, with generic examples you can adapt to IOS-XR, NX-OS, Junos, FRR, Arista EOS or your automation system.

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EVPN/VXLAN Anycast Gateway Troubleshooting: A Practical Leaf-Spine Checklist

EVPN/VXLAN anycast gateway troubleshooting is easiest when you separate the underlay, BGP EVPN control plane, VNI mapping and host evidence instead of staring at one broken ping. The common failure pattern is simple: hosts in the same rack work, but inter-rack or inter-subnet traffic fails after a new VLAN, VRF or leaf pair is added.

This checklist is vendor-neutral, but the commands use familiar NX-OS style wording because many data-center fabrics expose EVPN state in that form. Adapt the command names to your platform and keep the verification order. If you are new to the fabric vocabulary, start with the Data Center hub and the Start Here page.

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EVPN/VXLAN Troubleshooting Checklist: Fix Host Reachability in a Leaf-Spine Fabric

EVPN/VXLAN troubleshooting becomes much easier when you stop treating it as a magic overlay and split the fault into three layers: local switching, BGP EVPN control plane and VXLAN data plane. This guide gives a practical checklist for the common case: two endpoints should communicate through a leaf-spine fabric, but ping, ARP, TCP or a VM migration test fails.

The examples use documentation-style names such as leaf-1, vni-10100 and RFC 5737/RFC 3849 addressing. Replace them with your platform commands and real values in the lab, but keep the same order of operations.

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