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[MX] Behavior of logical interface when logical interface at other end is administratively shut down

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Article ID: KB36370 KB Last Updated: 29 Dec 2020Version: 1.0
Summary:
 

This article describes the behavior of a logical interface when the logical interface at the other end is administratively shut down.

 

Symptoms:
 

Topology

MX1(ge-1/0/1)---------(ge-1/0/0)MX2

Unit 0 and unit 1 are configured with vlan-id 10 and 20, respectively, with IP addressing on both routers, in the above topology.

labroot@MX1> show configuration | match ge-1/0/1 | display set
set interfaces ge-1/0/1 flexible-vlan-tagging
set interfaces ge-1/0/1 unit 0 vlan-id 10
set interfaces ge-1/0/1 unit 0 family inet address 10.1.1.1/24
set interfaces ge-1/0/1 unit 1 vlan-id 20
set interfaces ge-1/0/1 unit 1 family inet address 10.2.1.1/24

labroot@MX2> show configuration |display set| match ge-1/0/0
set interfaces ge-1/0/0 flexible-vlan-tagging
set interfaces ge-1/0/0 unit 0 vlan-id 10
set interfaces ge-1/0/0 unit 0 family inet address 10.1.1.2/24
set interfaces ge-1/0/0 unit 1 vlan-id 20
set interfaces ge-1/0/0 unit 1 family inet address 10.2.1.2/24

labroot@MX1> show interfaces terse | match ge-1/0/1
ge-1/0/1                up    up
ge-1/0/1.0              up    up   inet     10.1.1.1/24
ge-1/0/1.1              up    up   inet     10.2.1.1/24
ge-1/0/1.32767          up    up   multiservice

labroot@MX2> show interfaces terse | match ge-1/0/0
ge-1/0/0                up    up
ge-1/0/0.0              up    up   inet     10.1.1.2/24
ge-1/0/0.1              up    up   inet     10.2.1.2/24
ge-1/0/0.32767          up    up   multiservice

Disabled interface ge-1/0/1 unit 0 on MX1 router:
[edit]
labroot@MX1# set interfaces ge-1/0/1 unit 0 vlan-id 10 disable

[edit]
labroot@MX1# commit
commit complete

When unit 0 is disabled on MX1 router, the logical interface goes down, but at the other end, the logical interface stays up.

labroot@MX1> show interfaces terse | match ge-1/0/1
ge-1/0/1                up    up
ge-1/0/1.0              down  up   inet     10.1.1.1/24
ge-1/0/1.1              up    up   inet     10.2.1.1/24
ge-1/0/1.32767          up    up   multiservice

labroot@MX2> show interfaces terse | match ge-1/0/0
ge-1/0/0                up    up
ge-1/0/0.0              up    up   inet     10.1.1.2/24
ge-1/0/0.1              up    up   inet     10.2.1.2/24
ge-1/0/0.32767          up    up   multiservice

 

Solution:
 

This is expected behavior. The logical interface port status depends on the underlying physical interface status. The port status of the logical interface changes according to the underlying physical interface status on the local device.

 

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