Juniper EX: Troubleshoot an IRB or VLAN Interface (KB22220)

An IRB (integrated routing and bridging) interface — also called a VLAN interface — that refuses to come up is one of the most common Juniper EX support cases, and the cause is usually a chain of simple checks rather than a single exotic failure. This resolution guide, adapted from Juniper KB22220, walks the exact decision tree Juniper support engineers use: admin status first, then link status, then VLAN-to-interface mapping, and finally the physical layer. Each step includes the legacy and ELS command variants so it works across EX and QFX platforms alike.

Step 1 — Check the Admin Status

Display the admin and link state of the IRB or VLAN interface:

root@switch> show interfaces irb.15 terse          # ELS
root@switch> run show interfaces vlan.10 terse     # legacy

If Admin is Down, the interface was administratively disabled. Confirm with show configuration interfaces | display set — you will see set interfaces vlan unit 30 disable. Re-enable it (check with the network owner first, as it alters topology):

delete interfaces vlan unit 30 disable      # legacy
delete interfaces irb unit 15 disable       # ELS

Step 2 — Check the Link Status

If Admin is up but Link is Down, the IRB has no active member in the VLAN. Verify that the physical interfaces are mapped to the VLAN:

root@switch> show vlans DATA-1
Name       Tag     Interfaces
DATA-1     10      ae0.0, ge-0/0/0.0*, ge-0/0/3.0, ge-0/0/10.0

Missing members? Add them:

set interfaces ge-0/0/0 unit 0 family ethernet-switching vlan members DATA-1

Step 3 — Confirm an Active Member Exists

An IRB can only be up if at least one physical interface in the VLAN is active. The asterisk (*) marks the active connection:

root@switch> show vlans TEST
Name   Tag  Interfaces
TEST   30   ge-0/0/0.0*, ge-0/0/1.0

• Yes, there is a * — your IRB should be up. If it is still down, contact support.
• No * — work through the physical-interface resolution guide (KB19797) for every member without an asterisk, then the IRB should come up.

Rollback Safety

If any configuration change goes wrong, roll back immediately and commit:

rollback 1
commit

Related Junos troubleshooting: inter-VLAN communication on EX Series, EVPN MAC-VRF validation on ACX7000, and SR-TE LSPs through a multi-domain network.

原文链接：https://supportportal.juniper.net/s/article/Resolution-Guide-EX-Troubleshoot-VLAN-Interface