EIGRP Metric and K-Values Explained: Formula, Examples and Troubleshooting

EIGRP metric questions usually test three things: which inputs matter by default, how bandwidth and delay combine, and why mismatched K-values prevent neighbors from forming.

Short answer: with default K-values, EIGRP uses minimum path bandwidth and cumulative delay; for classic metrics, the calculation is 256 × (10^7 / minimum bandwidth in kbps + total delay in tens of microseconds).[1] K1 and K3 default to 1; K2, K4 and K5 default to 0, so load and reliability do not contribute to the default calculation.[1]

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RoCE PFC Buffer Sizing Guide: 400G Headroom Worksheet and ECN Checklist

A GPU cluster can pass a quiet link test and still collapse under synchronized traffic. Before buying switches with a bigger advertised buffer, ask a more precise question: how much traffic can arrive after a congested port requests a pause, and where can that traffic be stored? This guide provides a headroom worksheet, an incast calculation and a deployment test matrix for that decision.

The worked design is hypothetical: 32 servers, eight GPUs per server, and a selected 400 Gb/s Ethernet fabric. Calculations are executed arithmetic, not benchmark measurements or validated switch settings. The configuration examples are explicitly pinned to NVIDIA Cumulus Linux 5.9 documentation; they are not claims about the newest release or every Spectrum generation. Use your actual ASIC, network operating system and NIC support matrix before making changes.

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EIGRP Stuck in Active Explained: SIA Troubleshooting and Prevention

EIGRP Stuck in Active (SIA) means that a route's distributed computation has not received a required Reply within the permitted time; Cisco implementations can reset the unresponsive neighbor and remove routes learned through it.[1] For an interview, distinguish normal Active route computation from Stuck in Active, then explain how you would trace the missing reply and reduce query scope.[1][2]

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Weekly BGP Table Watch: IPv4, IPv6 and ASN Changes — 2026-09-28

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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Palo Alto SSL Decryption Breaking Applications: Troubleshooting Matrix and Exception Checklist

When an application stops working after SSL decryption is enabled, the useful question is not simply “should we bypass it?” It is: which connection leg failed, which certificate did the client receive, and what evidence distinguishes a trust problem from certificate pinning? This guide provides a troubleshooting matrix, a controlled comparison workflow and an exception-review worksheet for Palo Alto Networks SSL Forward Proxy deployments.

Scope: outbound SSL Forward Proxy, not inbound inspection or a GlobalProtect portal certificate. The worksheets and hypothetical example are original operational recommendations, not a report of executed firewall tests. Confirm menus, log availability and supported settings against your PAN-OS release and management platform before using them.

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Network freak Weekly Roundup: 2026-W39

This is the weekly Network freak roundup for 2026-W39. It collects the latest practical networking articles published this week, so the X feed can stay quiet while readers still get all links in one place.

EIGRP Successor and Feasible Successor Explained: FD, RD and Feasibility Condition

A second EIGRP path is not automatically a ready-to-use backup. The interview question is: what makes a neighbor a successor or feasible successor, and which distances does EIGRP compare?

Short answer: a successor is a neighbor providing a least-cost path that satisfies EIGRP's feasibility condition; a feasible successor is a neighbor whose reported distance is strictly less than the local feasible distance for that destination.[1]

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Top 10 Claude Opus 5.5 Projects and Demos: What It Does Better Than GPT-6 Astra

Claude Opus 5.5 is producing its strongest public demos where code becomes the medium: games, browser worlds, explainer videos, visual tools, repo analysis, and long-running agent workflows. The best examples are not ordinary chat answers. They are artifacts that can be opened, tested, inspected, or replayed.

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Palo Alto Configuration Rollback Checklist: Revert vs Load vs Panorama Push

A Palo Alto firewall change has broken an application. You click Revert to running configuration, but the outage remains. The key distinction: that operation discards uncommitted candidate edits; it does not undo the configuration that is already running. To restore an older committed firewall configuration, load the intended saved version and commit it after reviewing the differences.[1]

This guide answers how to roll back a Palo Alto configuration safely, including the additional deployment boundary introduced by Panorama. It provides a decision table, a change-control worksheet and a recovery acceptance matrix. The workflow is an original operational recommendation, not a record of a production incident or a tested recovery-time guarantee.

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HSRP vs VRRP vs GLBP Explained: Preempt, Tracking and Failover

HSRP vs VRRP vs GLBP is not just a question about protocol names. The useful interview question is: which router forwards for the default gateway, what makes that responsibility move, and what happens when only the upstream path fails?

Short answer: HSRP uses an active/standby model for a group; VRRP elects an Active Router with Backup Routers for a virtual router; GLBP separates the active virtual gateway (AVG) from active virtual forwarders (AVFs), allowing multiple routers to forward for the same virtual IP through different virtual MAC addresses.[2][1][3]

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F5 BIG-IP Disabled vs Forced Offline: Pool Member Drain Checklist

You disable an F5 BIG-IP pool member for maintenance, but requests keep arriving. That does not necessarily mean the command failed: a Disabled member can still accept new connections belonging to an existing persistence session.[6] The operational question is not simply “is the icon disabled?” but “which traffic must stop, and what evidence proves it has stopped?”

This guide provides a Disabled-versus-Forced-Offline decision table, a staged maintenance runbook, and an acceptance matrix. It is about intentional traffic withdrawal—not fixing a failed health monitor. Examples are fictional, commands are unexecuted templates, and no production maintenance or performance test is claimed.

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Claude Opus 5.5 Capability Deep Dive: Coding Agents, Computer Use and Real-World Limits

Claude Opus 5.5 is best understood as an agent model, not just a smarter chat model. The useful question is not whether it can answer a prompt nicely. The useful question is whether it can hold a large codebase or work package in context, call tools safely, recover from mistakes, and finish multi-step work at a cost that makes sense.

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Claude Opus 5.5 Current News Update: Availability, Copilot Rollout, Pricing and Builder Reaction

Claude Opus 5.5 is no longer just a launch announcement. It is now a live model in the Claude API, Claude Code, major cloud platforms and GitHub Copilot, with early public testing focused less on chat and more on long-running agent work. The practical question for builders is not whether the benchmark chart is impressive. It is whether the model is cheaper to run, easier to govern, available in the tools teams already use, and reliable enough for unattended coding or knowledge-work loops.

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LACP EtherChannel Explained: Active vs Passive, Link Limits and Load Balancing

What is LACP EtherChannel, and why does active/passive matter? EtherChannel groups compatible physical Ethernet links into one logical port-channel; LACP negotiates membership rather than forcing links into a static bundle.[1]

Short answer: active starts LACP negotiation, passive responds, and passive/passive does not form an LACP bundle.[1] For the Catalyst 9300 release documented here, an LACP group supports up to eight active members plus up to eight standby members; treat that as a platform limit, not a universal definition of LACP.[1]

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AI GPU Cluster Acceptance Checklist: A 256-GPU NCCL and DCGM Test Plan

A GPU cluster is not ready for handover just because every server boots and one AllReduce finishes. The buyer needs a repeatable answer to a narrower question: does this exact hardware and software build deliver correct, stable communication across every intended failure domain, and can operations reproduce the evidence?

This AI GPU cluster acceptance checklist turns that question into a staged test plan for a hypothetical 256-GPU deployment. The durable assets are a commissioning matrix, coverage worksheet, evidence manifest and sign-off gates. It is a handover guide, not another list of NCCL tuning variables. All sizing figures are calculated examples; no GPU benchmarks were executed for this article.

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