[j-nsp] JunOS 18, ELS vs non-ELS QinQ native vlan handling.

[Alexandre Snarskii]

On Fri, Mar 22, 2019 at 04:21:47PM -0400, Andrey Kostin wrote:
> Hi Alexandre,
> 
> Did it pass frames without C-tag in Junos versions < 18?

Yes. 

tcpdump from upstream side when switch running 17.4R1-S6.1:

tcpdump: listening on ix1, link-type EN10MB (Ethernet), capture size 262144 bytes
17:59:15.742379 0c:c4:7a:93:a6:8e > ff:ff:ff:ff:ff:ff, ethertype 802.1Q (0x8100), length 64: vlan 171, p 0, ethertype ARP, Ethernet (len 6), IPv4 (len 4), Request who-has 10.11.1.2 tell 10.11.1.1, length 46
17:59:16.773827 0c:c4:7a:93:a6:8e > ff:ff:ff:ff:ff:ff, ethertype 802.1Q (0x8100), length 64: vlan 171, p 0, ethertype ARP, Ethernet (len 6), IPv4 (len 4), Request who-has 10.11.1.2 tell 10.11.1.1, length 46

exactly the same setup, switch upgraded to 18.3R1-S2.1:

18:19:28.535143 0c:c4:7a:93:a6:8e > ff:ff:ff:ff:ff:ff, ethertype 802.1Q (0x8100), length 68: vlan 171, p 0, ethertype 802.1Q, vlan 1, p 0, ethertype ARP, Ethernet (len 6), IPv4 (len 4), Request who-has 10.11.1.2 tell 10.11.1.1, length 46
18:19:29.598700 0c:c4:7a:93:a6:8e > ff:ff:ff:ff:ff:ff, ethertype 802.1Q (0x8100), length 68: vlan 171, p 0, ethertype 802.1Q, vlan 1, p 0, ethertype ARP, Ethernet (len 6), IPv4 (len 4), Request who-has 10.11.1.2 tell 10.11.1.1, length 46

as you see, packets that were transferred with only S-vlan tag
now encapsulated with both S-vlan and 'native' vlan..


> 
> Kind regards,
> Andrey
> 
> Alexandre Snarskii писал 2019-03-22 13:03:
> > Hi!
> > 
> > Looks like JunOS 18.something introduced an incompatibility of native
> > vlan handling in QinQ scenario between ELS (qfx, ex2300) and non-ELS
> > switches: when ELS switch forwards untagged frame to QinQ, it now adds
> > two vlan tags (one specified as native for interface and S-vlan) 
> > instead
> > of just S-vlan as it is done by both non-ELS and 'older versions'.
> > 
> > As a result, if the other end of tunnel is non-ELS (or third-party)
> > switch, it strips only S-vlan and originally untagged frame is passed
> > with vlan tag :(
> > 
> > Are there any way to disable this additional tag insertion ?
> > 
> > PS: when frames sent in reverse direction, non-ELS switch adds only
> > S-vlan and this frame correctly decapsulated and sent untagged.
> > 
> > ELS-side configuration (ex2300, 18.3R1-S1.4. also tested with
> > qfx5100/5110):
> > 
> > [edit interfaces ge-0/0/0]
> > flexible-vlan-tagging;
> > native-vlan-id 1;
> > mtu 9216;
> > encapsulation extended-vlan-bridge;
> > unit 0 {
> >     vlan-id-list 1-4094;
> >     input-vlan-map push;
> >     output-vlan-map pop;
> > }
> > 
> > (when native-vlan-id is not configured, untagged frames are not
> > accepted at all).
> > 
> > _______________________________________________
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>