Step-by-step Junos troubleshooting: BGP flaps, L2 loops, interface errors and log analysis.
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.
MAC learning storms of invalid addresses, packets flooded out every port, unknown-unicast floods — the Juniper community sees this EX-series problem weekly. The causes are usually one of four: a loop, silent P2P failures, asymmetric routing or a leaking device.
BGP stuck in Active or Connect means TCP never establishes. This guide covers the real-world causes from Juniper forums: missing routes, loopback peering without local-address, eBGP multihop, blocked TCP/179 and auth mismatch.
OSPF neighbors stuck in ExStart is one of the most common Junos troubleshooting questions on the Juniper community. Most of the time it is an MTU mismatch — here is how to confirm it in 60 seconds and fix every other cause too.
An EX3400 Virtual Chassis that shows a missing member after a reboot, or splits into two masters, is one of the most-searched EX-series problems. Here is how split-and-merge works and the command path to recover cleanly.