Juniper routes and neighbor checks cheat sheet
Inspect routes, ARP entries and discovered neighbors in Junos.
Junos operational mode; LLDP and routing-instance behavior depend on configuration.
Updated · Juniper · 7 min read
| Command | What it does |
|---|---|
show route | Inspect the routing table |
show arp no-resolve | Inspect IPv4 neighbor mappings |
show lldp neighbors | Read adjacent device information |
show interfaces extensive | Inspect detailed interface counters |
Walkthrough
Use an operational read account. Confirm whether the workload uses the default routing table or a separate routing instance.
Step 1: Inspect the routing table
show route
Identify the active route marker, protocol and next hop. For non-default routing instances, inspect the correct table rather than assuming the global table applies.
Step 2: Inspect IPv4 neighbor mappings
show arp no-resolve
Compare learned neighbors with directly attached subnets. no-resolve avoids DNS name lookup and keeps the output focused on addresses.
Step 3: Read adjacent device information
show lldp neighbors
Map local and remote ports to the cabling plan. Empty output can mean LLDP is disabled or unsupported on either endpoint.
Step 4: Inspect detailed interface counters
show interfaces extensive
Focus on the affected interface and compare error trends over time. This broad command can produce large output; use an interface-specific form after locating the port.