Routing

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  • 1.  What is the practical use of encapsulation-type knob under 'protocols l2circuits'

     
    Posted 06-24-2015 05:39

    Hi,

     

    Junos documentation says that if configured, the encapsulation-type knob under 'protocols l2circuits' will specify the L2circuit encapsulation advertised in the PE's FEC128. If not configured, the PE's AC interface encapsulation configuration will be what's advertised in the PE's FEC128.

     

    But configuring the PE's AC encapsulation is mandatory for bringing up an L2circuit, with or without the encapsulation-type knob, which means the AC interface encapsulation will always be configured. So what is the practical benefit of configuring the same encapsulation under 'protocols l2circuit' as illustrated below? Are there scenarios in which we want the encapsulation types configured on the PE's AC interface and under 'protocols l2circuit' to be different?

     

    [edit]

    regress@PE1# show interfaces ge-4/0/1

    vlan-tagging;

    encapsulation vlan-ccc; <<<<<<

    unit 512 {

        encapsulation vlan-ccc;  <<<<<

        vlan-id 512;

    }

     

    [edit]

    regress@PE1# show protocols l2circuit

    neighbor 3.3.3.3 {

        interface ge-4/0/1.512 {

            virtual-circuit-id 1;

            encapsulation-type ethernet-vlan;    <<<<<<<<<<  What is this useful for? Everything works fine without it.

        }

    }

     

     



  • 2.  RE: What is the practical use of encapsulation-type knob under 'protocols l2circuits'
    Best Answer

    Posted 06-24-2015 08:07

    Hello,

    Consider the scenario where You want to transport a bunch of VLANs over single PW. The working config is:

     

    [edit]
regress@PE1# show interfaces ge-4/0/1
vlan-tagging;
encapsulation vlan-ccc; <<<<<<
unit 512 {
    encapsulation vlan-ccc;  <<<<<
    vlan-id-list [ 512 514 516 518 520 ];
}
 
[edit]
regress@PE1# show protocols l2circuit
neighbor 3.3.3.3 {
    interface ge-4/0/1.512 {
        virtual-circuit-id 1;
        encapsulation-type ethernet;    
    }
}

    If memory serves, leaving the PW encaps to defaults in this sutuation means the PW will be signalled with Type-4 (VLAN-based) and 1st VLAN in the list will be used. Which creates problems adding or removing VLANs since each time the 1st VLAN changes, the PW is resignaled and possibly fails because of far-end VLAN mismatch.

    Hence You need either "encapsulation-type etherbet-vlan"+"ignore-vlan-mismatch" or simply "encapsulation-type ethernet" - the latter is more powerful since it allows to decouple ingress interface encaps from PW type.

    HTH

    Thanks

    Alex