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

[Alexandre Snarskii]

On Tue, Jul 23, 2019 at 01:45:19AM +0200, Olivier Benghozi wrote:
> 4 months old thread, but (since I'm starting to test some QinQ stuff just 
> now), I found both this thread and its «solution»:
> 
> PR1413700
> «Untagged traffic is single-tagged in Q-in-Q scenario on EX4300 platforms»
> «On EX4300 platforms except for EX4300-48MP with Q-in-Q configured, untagged 
> traffic over S-VLAN is forwarded with a single tag, whose processing behavior 
> is not in line with other products (e.g., the MX platforms) and other providers
> (e.g., Cisco). If Q-in-Q is configured between these devices with different
> processing behavior of untagged traffic, this might cause the untagged traffic
> loss.»
> 
> So if I understand well, they suddenly chose compatibility with Cisco & MX 
> instead of compat with old EX (whereas an option would have been fine).
> The problem is: I'm not sure at all that it's really the case on Cisco gears...

According to our SE, this behaviour will be configurable in 18.3R3, 18.4R3 
and 19.1R2.

> 
> 
> > Le 24 mars 2019 à 16:36, Alexandre Snarskii <snar at snar.spb.ru> a écrit :
> > 
> > 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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