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  • 1.  MC-LAG with RSTP on EX4600

    Posted 04-12-2021 02:27
    Hi,

    I am working on setting up MC-LAG on two EX4600 towards EX4300 as "client".
    But due to existing topology, the layout is as follows:

    --trunk-to-other-EX-device-RSTP-->[EX4600]<-->[EX4600]<--trunk-to-other-EX-device-RSTP--
    The EX4600 is connected with 1 RSTP trunk, and 1 ICCP/ICL interface.
    The EX4300 is connected (will be) to both EX4600. 
    The links "other-EX" is a part of the existing RSTP-domain.
    To maintain the availability with the loop and traffic, we need, for some time, run both RSTP and MC-LAG.

    We were recommended (based from Junipers homepage about MC-LAG) to remove all mcae-VLANs from the RSTP trunk and add them to the non-RSTP-ICL/ICCP link.
    At this point, the mcae was not up.
    We noticed that some hosts, connected directly to the EX4600 couldnt ping/connect to devices in other parts of the network. I guess ARP-issues.

    What I was thinking as a possible cause within this scenario is maybe, maybe.... we should have "all VLANs" allowed on the RSTP-trunk (except ICCP) and also have the same VLANs allowed on the ICL-trunk, to get the traffic to flow between the EX4600 as before, since i think that is a major part of the issue we've seen.

    Any inputs or ideas on this scenario is welcome.
    I have not seen any good documentation from Juniper on this kind of scenario, but are still searching :)

    //Rob

    ------------------------------
    Rob
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  • 2.  RE: MC-LAG with RSTP on EX4600

    Posted 04-12-2021 03:13
    Hi Rob ,

    Good day !
    To be more specific can you provide the below details

    >by connectivity issues do you see connectivity issue on the same vlan or different vlan 
    >if this device (ex4600) is used as layer 3 then we need to use VRRP for layer 3 connectivity 
    >stp should not be enabled in MC-ae interface and the ICL and iccp 
    >need to use different like for icl and iccp 
    >RSTP can be used on non mc-ae interfaces 
    >have you check the arp and the ethernet switching table at the time of issue 
    >the forwarding table 

    Regards ,
    Sharanya


  • 3.  RE: MC-LAG with RSTP on EX4600

    Posted 04-12-2021 10:56
    Hi Sharanya,
    It was a VLAN that was enabled on the ICL link, and removed on the RSTP-link that is running between the EX4600.
    STP is not enabled on the ICL, neither on the mcae (which we have not yet been enabling, due to the issue occurred before we came that far).
    The ICL and ICCP is running on the same ae-interface. ICCP on VLAN X with IRB-interfaces.

    The topology holds a few legacy things, such as;
    (1)EX4600 <-> (2)EX4600
    The number 1 has a couple of IRB interfaces, running VRRP, with another device located in the network.
    We did not check the arp table during the issue, we just noticed that it couldnt reach the other node over the network, so we performed full rollback.
    I also suspect that the RSTP-break/BLK togheter with my ideas that the ICL didnt forward traffic between "2" to "1" as a regular trunk-port should, did make this issue occur.
    One of the main questions here is if we should have the following between the EX4600
    1 ae for ICL/ICCP with the mcae-VLANs+ICL
    1 ae for RSTP-trunk with all-except-ICP. (As of now, we removed all VLANs that was specified on the ICL, as we thought that would do the necessary job and forward traffic)
    Since, if the EX4600(2) has a BLK on the right side... it will not use that link, as traffic will be a mess if the ICL isnt trunking the VLANs as regular trunks do, in any case of mcae up or down (as it was down now, if that makes any difference).


  • 4.  RE: MC-LAG with RSTP on EX4600

    Posted 04-13-2021 06:06
    Hi Rob ,

    Good day !
    Thank you for the information , i am still confused about the network topology 

    But usually if its the DC environment , the L3 is done at the mc-lag or at a core to maintain consistency

    1 ae for ICL/ICCP with the mcae-VLANs+ICL -

    Answer :it is recommended to have 1 link for icl one separate link for ICCP 

    1 ae for RSTP-trunk with all-except-ICP. (As of now, we removed all VLANs that was specified on the ICL, as we thought that would do the necessary job and forward traffic) -

    Answer :u need to take all the vlans on the ICL and have a separate vlan for ICCP to synchronise traffic 

    Refer to the below link for best practices : https://www.juniper.net/documentation/us/en/software/junos/mc-lag/topics/concept/best-practices-usage-notes.html

    MC-lag configuration : https://www.juniper.net/documentation/us/en/software/junos/mc-lag/topics/topic-map/examples-mc-lag.html 

    I hope this document was useful 

    Regards 
    Sharanya