Step-by-step Junos troubleshooting: BGP flaps, L2 loops, interface errors and log analysis.
A Juniper EX BPDU error means a BPDU-protected port received a spanning tree BPDU, so Junos shut it down until someone clears it. This guide shows how to confirm the error, find the source, clear it on ELS and non-ELS switches, and set auto-recovery without creating a flapping loop.
An SRX chassis cluster node goes disabled to prevent split brain, usually after the control link or fabric link fails. This guide shows how to read the Events reason, checks both links in order from cheapest to most expensive, ranks the root causes, and explains how to bring the node back safely.
A Junos LACP ae interface that stays down is usually caused by the far end, not the Juniper box. Here is an ordered diagnostic, with root causes ranked by how often we see them, to get from Defaulted or Detached to Collecting distributing.
'My SRX345 is at 100% CPU' and 'EX switch high CPU' are constant Reddit and Juniper KB topics. Learn to identify rpd, snmpd, httpd and eventd as the culprit process and apply the right fix for each.
NMS dashboards full of 'SNMP timeout' on Juniper gear is a permanent support-checklist item. Juniper's own SNMP troubleshooting checklist covers the causes — polling method, bulk walks, large tables and firewall filtering. Here they are, in field order.
'Input errors are climbing — is it the cable, the optic or the config?' Juniper KB and Reddit threads answer this constantly. Here is every counter in show interfaces extensive explained, with the isolation method that finds the guilty component.