https://ittechnetworkk.co.uk/tags/nxos/ Recent content in Nxos on ittechnetworkk Hugo en-US Wed, 08 Apr 2026 10:00:00 +0200 https://ittechnetworkk.co.uk/posts/vpc-nexus-9k/ Wed, 08 Apr 2026 10:00:00 +0200 https://ittechnetworkk.co.uk/posts/vpc-nexus-9k/ <h2 id="what-is-vpc">What is vPC?</h2> <p>Virtual Port Channel (vPC) lets two Nexus switches appear as a single logical switch to downstream devices. Connected hosts or switches see one port-channel spanning both peers — if one peer fails, traffic continues through the other with no STP reconvergence.</p> <p><strong>Key components:</strong></p> <ul> <li><strong>vPC Peer Link</strong> — carries BPDUs, HSRP, control traffic, and orphan port traffic between the two peers. Always a port-channel with at least two 10G/40G/100G members</li> <li><strong>vPC Peer Keepalive</strong> — a lightweight heartbeat (UDP 3200) used only to detect a dual-active (split-brain) scenario. Runs over a dedicated port-channel in a separate VRF — keeping it off the management plane for security and redundancy</li> <li><strong>vPC Member Ports</strong> — port-channels on each peer that share a common <code>vpc</code> ID, forming a single logical channel to the downstream device</li> <li><strong>vPC Domain</strong> — the logical grouping that binds the two peers together</li> </ul> <hr> <h2 id="topology">Topology</h2> <div class="highlight"><pre tabindex="0" class="chroma"><code class="language-fallback" data-lang="fallback"><span class="line"><span class="cl"> ┌──────────┐ ┌──────────┐ </span></span><span class="line"><span class="cl"> │ NEXUS-1 │ │ NEXUS-2 │ </span></span><span class="line"><span class="cl"> │ (vPC Pri)│ │ (vPC Sec)│ </span></span><span class="line"><span class="cl"> └──┬──┬──┬─┘ └─┬──┬──┬──┘ </span></span><span class="line"><span class="cl"> │ │ │ │ │ │ </span></span><span class="line"><span class="cl"> Keepalive──│──│──│───────────│──│──│──Keepalive </span></span><span class="line"><span class="cl"> (Po20/VRF) │ │ │ │ │ │ (Po20/VRF) </span></span><span class="line"><span class="cl"> │ │ └───────────┘ │ │ </span></span><span class="line"><span class="cl"> │ │ Peer Link │ │ </span></span><span class="line"><span class="cl"> │ │ (Po10: 2x40G) │ │ </span></span><span class="line"><span class="cl"> │ │ │ │ </span></span><span class="line"><span class="cl"> │ └────────┬────────┘ │ </span></span><span class="line"><span class="cl"> │ vPC Member │ </span></span><span class="line"><span class="cl"> │ (Po100: 2x10G) │ </span></span><span class="line"><span class="cl"> │ │ │ </span></span><span class="line"><span class="cl"> │ ┌────┴────┐ │ </span></span><span class="line"><span class="cl"> │ │ SERVER │ │ </span></span><span class="line"><span class="cl"> └──────┤ / ToR ├──────┘ </span></span><span class="line"><span class="cl"> └─────────┘</span></span></code></pre></div><hr> <h2 id="addressing-reference">Addressing Reference</h2> <table> <thead> <tr> <th>Device</th> <th>Interface</th> <th>IP Address</th> <th>Purpose</th> </tr> </thead> <tbody> <tr> <td>NEXUS-1</td> <td>Po20 (VRF VPC-KA)</td> <td>10.10.10.1/30</td> <td>Peer Keepalive</td> </tr> <tr> <td>NEXUS-2</td> <td>Po20 (VRF VPC-KA)</td> <td>10.10.10.2/30</td> <td>Peer Keepalive</td> </tr> <tr> <td>NEXUS-1</td> <td>Vlan100</td> <td>172.16.100.2/24</td> <td>HSRP VIP gateway</td> </tr> <tr> <td>NEXUS-2</td> <td>Vlan100</td> <td>172.16.100.3/24</td> <td>HSRP VIP gateway</td> </tr> <tr> <td>HSRP VIP</td> <td>—</td> <td>172.16.100.1/24</td> <td>Default gateway</td> </tr> </tbody> </table> <hr> <h2 id="configuration">Configuration</h2> <p>We&rsquo;ll build this in order — each step depends on the previous one.</p>