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use of the set vlan-tagging command in trunk mode

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  • 1.  use of the set vlan-tagging command in trunk mode

    Posted 04-14-2020 11:21

    Bonjour,

    I am configuring trunks on a EX2300 switch .

    My question is about the usefulness of the set vlan-tagging command.

    After configuring my vlans and creating 2 ports with the same set interface ,,, unit 0 family ethernet switching interface-mode trunk and vlan member statements  I see my trafic flowing flawlessly from one port to another.

    set interfaces ge-0/0/4 unit 0 family ethernet-switching interface-mode trunk
    set interfaces ge-0/0/4 unit 0 family ethernet-switching vlan members MRCRN_Vlans
    set interfaces ge-0/0/6 unit 0 family ethernet-switching interface-mode trunk
    set interfaces ge-0/0/6 unit 0 family ethernet-switching vlan members MRCRN_Vlans

    set vlans MRCRN_Vlans vlan-id-list 3350-3397

    So is there a use in adding a set vlan-tagging command ? 

    Juniper documentation says 

    To configure a device to receive and forward single-tag frames with 802.1Q VLAN tags, include the vlan-tagging statement at the [edit interfaces interface-name] hierarchy level:

    but my trunk seems to work perfectly without it. 

    just curious ...

    Thanks,

    Michel

     

     



  • 2.  RE: use of the set vlan-tagging command in trunk mode

     
    Posted 04-14-2020 12:26

    Hi Michel,

     

    It looks like the use of the vlan-tagging command is more a workaround for certain platforms, for example the MX platform will need this statement for a trunk port to work properly as you can see on below link,

    https://kb.juniper.net/InfoCenter/index?page=content&id=KB27031&cat=MX5_1&actp=LIST

     

    The 4 bytes of the vlan tag will not be added to the MTU until you configure the vlan-tagging statement, same applies for the EX92* platforms that are similar to the MX platforms. In your case the EX2300 device should be working properly without the need of this command, in fact it is not support to use it with the configuration you have as you can see here,

    https://www.juniper.net/documentation/en_US/junos/topics/reference/configuration-statement/vlan-tagging-edit-interfaces.html

     

    "On EX Series switches except for EX4300 and EX9200 switches, the vlan-tagging and family ethernet-switching statements cannot be configured on the same interface"

     

    Hope you find this information usefull for your concern.

     

    Please mark as Solved if this worked for you.

     

    Jeffry



  • 3.  RE: use of the set vlan-tagging command in trunk mode

    Posted 04-14-2020 18:21

    merci beaucoup Jeffry for the explanation. 

    interesting reading. 

    however, I am scared now: the Juniper note says that the configuration I am now running on 70 EX2300 installed in the field cannot be ...

     show interfaces ge-0/0/0  
    vlan-tagging;
    unit 0 {
        family ethernet-switching {
            interface-mode trunk;
            vlan {
                members Z-Legacy;
            }
            filter {
                input client-filter-1g;
                output client-filter-1g;
            }
            storm-control default;
        }
    }

    I clearly have vlan-tagging statement and family ethernet-switching on a EX serie switch .

    any thoughts ? 

    merci again,

    Michel

     



  • 4.  RE: use of the set vlan-tagging command in trunk mode
    Best Answer

     
    Posted 04-14-2020 18:59

    Hi Michel,

     

    You are very welcome, regarding the configuraiton you have, this could be a commit not introduced on certain codes, maybe the configuration is not giving you commit errors, however as mentioned the behavior of this platform is that by simply having the interface as trunk the 4 byte for the MTU would be added so no need of vlan-tagging command

     

    Please mark as Solved if this worked for you.

     

    Regards,

     

    Jeffry



  • 5.  RE: use of the set vlan-tagging command in trunk mode

     
    Posted 04-14-2020 19:22

    Agree with @Jeff33.  The command is accepted, as it is a 'standard' Junos command, but I believe it has no affect on certain specific platforms.  So you can set it, but it actually does nothing, neither good or bad.

     

    This is not that uncommon is Junos, seeing that this OS crosses many different products, each with its own best use cases.  Changing this behavior, would be VERY difficult to change, especially with how long Junos OS has been around, IMHO.