Routing

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  • 1.  Multiple same IPs on a device

    Posted 08-19-2022 17:53
    Recently I came across a scenario from Juniper Training Lab as follows:
    The virtual router has the same IPs on two interfaces.
    set interfaces ge-0/0/3 unit 60 family inet address 192.16.123.2/24
    set interfaces ge-0/0/4 unit 60 family inet address 192.16.123.2/24
    
    set routing-instances vpls-vr instance-type virtual-router
    set routing-instances vpls-vr interface ge-0/0/3.60
    set routing-instances vpls-vr interface ge-0/0/4.60
    
    root@LS-1# run show route table vpls-vr.inet.0
    
    vpls-vr.inet.0: 2 destinations, 2 routes (2 active, 0 holddown, 0 hidden)
    + = Active Route, - = Last Active, * = Both
    
    192.16.123.0/24    *[Direct/0] 00:46:29
                        > via ge-0/0/4.60
    192.16.123.2/32    *[Local/0] 00:46:29
                          Local via ge-0/0/4.60
    
    
    
    ​

    How is IP selected to be active ?
    How does it fail over to other interface ? automatically ? 
    after I disabled ge-0/0/4, I got the following:

    root@LS-1# run show route table vpls-vr.inet.0
    
    vpls-vr.inet.0: 1 destinations, 1 routes (1 active, 0 holddown, 0 hidden)
    + = Active Route, - = Last Active, * = Both
    
    192.16.123.2/32    *[Local/0] 00:48:50
                          Reject
    

    Any docs talk about this ?

    thanks !!









  • 2.  RE: Multiple same IPs on a device

    Posted 08-21-2022 19:52
    That scenario is not valid, the duplicate ip address in the same layer 2 domain will not create a good situation.

    Can you share the document where this is recommended so we can evaluate what adjustment needs to be made?

    ------------------------------
    Steve Puluka BSEET - Juniper Ambassador
    IP Architect - DQE Communications Pittsburgh, PA (Metro Ethernet & ISP - Retired)
    http://puluka.com/home
    ------------------------------



  • 3.  RE: Multiple same IPs on a device

    Posted 08-21-2022 21:41
    As this is not allowed in Cisco. So I was so surprised to see it. It is done in one of the Juniper training Lab.  The VPLS routers are configured as multihome. Originally I thought I should have used ae interfaces facing two VPLS routers. But the lab uses the above setting. very odd.

    I just like to make sure nothing I missed.

    thanks for taking a look!!


  • 4.  RE: Multiple same IPs on a device

    Posted 08-22-2022 06:09
    There is a feedback button on Juniper pages where comments like this can be sent to the page owner.  It would be good to report this issue so the Juniper education team could fix the example.

    ------------------------------
    Steve Puluka BSEET - Juniper Ambassador
    IP Architect - DQE Communications Pittsburgh, PA (Metro Ethernet & ISP - Retired)
    http://puluka.com/home
    ------------------------------



  • 5.  RE: Multiple same IPs on a device

    Posted 08-22-2022 10:58
    I already did. The Juniper Education team has always been very nice to offer help.

    thanks a lot !!


  • 6.  RE: Multiple same IPs on a device

    Posted 08-22-2022 18:06
    Gongya,

    I have responded to your query about this through the Zendesk ticket you submitted.

    In the setup being used (vr-configs), it is not important that we used the same IP address because with the VPLS multihoming we have you configure,  only one of the multihomes PEs to be active at a time so there will only be one connection to that IP at any given time. I don't necessarily think it is reality (or even good practice (I would choose to do it quite different)) to have this setup, but we reuse a lot of configurations from other parts of the SSB to simulate connections that may not be there or provide actual communication through you core. The VR device configurations are very complex and there is a lot going on there which makes it difficult to build unique configurations for each chapter and super lab individually..

    Please let me know through the Zendesk ticket if my explanation provides some clarity for you on the setup.

    ------------------------------
    Josh Verhaal
    ------------------------------



  • 7.  RE: Multiple same IPs on a device

    Posted 08-22-2022 18:23
    thanks so so so much for your explanation !!!


  • 8.  RE: Multiple same IPs on a device

    Posted 08-24-2022 15:43
    Just wanted to update this thread with the changes made to make it a bit more real world and work according to plan. We changed the two physical interfaces to bridge (l2 interfaces) and configured an IRB with the IP. We also created bridge domain with the IRB as the routing interface. That way the VPLS connections came in layer 2 interface and the overlay IP connectivity from CE1 terminated at the same IP on CE2.

    ------------------------------
    Josh Verhaal
    ------------------------------



  • 9.  RE: Multiple same IPs on a device

    Posted 08-24-2022 16:13
    WOW, You are so diligent and serious about this.

    A million thanks !!


  • 10.  RE: Multiple same IPs on a device

    Posted 08-24-2022 16:13
    Thanks for making that adjustment and follow up.  Definitely using an irb interface in the bridge domain is more normal real world deployment.

    ------------------------------
    Steve Puluka BSEET - Juniper Ambassador
    IP Architect - DQE Communications Pittsburgh, PA (Metro Ethernet & ISP - Retired)
    http://puluka.com/home
    ------------------------------