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  • 1.  Unnumbered interface with bridge-domain

    Posted 10-11-2019 02:56


    There is a problem that I just can’t figure out 🙂
    Juniper MX80 has three vlan 10,20,30 on tagged port ge-1/1/8 with vlan-per user clients which use static IP addressing through unnumbered.

    Here is a part of a working configuration:

    Loopback interface

    interfaces lo0
    unit 0 {
         family inet {

    Access interfaces

    interfaces ge-1/1/8 {
    encapsulation flexible-ethernet-services;
    unit 20 {
          vlan-id 20
          family inet {
            unnumbered-address lo0.0;
    unit 30 {
         vlan-id 30
         family inet {
            unnumbered-address lo0.0;

    Route to client

    static {
        route {
            qualified-next-hop ge-1/1/8.20;
        route {
            qualified-next-hop ge-1/1/8.30;

    We run a STP ring to theese clients to improve connectivity and now that vlans can be reached out via ge-1/1/7 or ge-1/1/8 tagged ports. I decided to do this through the bridge-domain and irb interface, but there is a restriction that that does not allow setting an unnumbered address on the irb interface. For now I decided to put a copper patch or logical-tunnel between the ports in the router to collect these vlan at one point and terminate them with unnumbered.
    But this scheme seems to be wrong.


    Is it a technical limitation of the architecture?

    Any other correct way?

    Thank you in advance!



  • 2.  RE: Unnumbered interface with bridge-domain

    Posted 10-11-2019 03:08



    I assume unnumbered addresses are meant for P2P interfaces and since irb are not P2P, an unnumbered address is not supported.




  • 3.  RE: Unnumbered interface with bridge-domain
    Best Answer

    Posted 10-11-2019 03:30

    Bridge domains are layer 2 interface bridges.  The only layer 3 address allowed is the one you create for the bridge itself.


    You can only add layer 2 interfaces to the bridge and only when they are family bridge.  So an unnumbered layer 3 family inet interface would not be allowed.


  • 4.  RE: Unnumbered interface with bridge-domain

    Posted 10-11-2019 04:42

    thanks for your replies!

    As I understand it, the physical loop between the two ports is the only way out in this situation?

  • 5.  RE: Unnumbered interface with bridge-domain

    Posted 10-12-2019 02:32

    It sounds like you don't really need the links to be layer 3 at all for this connection.


    If that is true you could simply remove the family inet unnumbers and convert the links to family bridge and place them directly into your per vlan bridge domain.


  • 6.  RE: Unnumbered interface with bridge-domain

    Posted 03-01-2022 09:42
    I do see why they have done it, but i can't see that there is any reason for it.

    If you wanted a dedicated link between 2 switches, and can't use IRB for point to point links, you have 2 option, both cost more to do:
    1. use a /31. More work with manage IP-address's, and configuration, then a IRB with UN.
    2. use a dedicated interface. Needs dedicated ports, fiber , physical work.

    *3. Set a interface a unnumbered, set a different interface a access.  More config, dedicated ports,  SFP, physical work. (If you really want to use unnumbered address)