Description

This article explains the behavior change of untagged traffic over S-VLAN from single tag (S-VLAN tag) to double tag (native-VLAN and S-VLAN tag) in different EX and QFX hardware platforms and Junos OS.

 

Symptoms

Note that untagged traffic over S-VLAN changes from single tag to double tags (for example, starting from 14.1X53-D47 for EX4600). With such change, when S-VLAN is stripped in Remote PE, untagged traffic becomes tagged with native-VLAN. 

Below is a Q-in-Q config example for EX4600 with native-vlan-id 300 in UNI:

set interfaces ge-0/0/6 flexible-vlan-tagging
set interfaces ge-0/0/6 encapsulation extended-vlan-bridge
set interfaces ge-0/0/6 unit 100 vlan-id 100
set interfaces ge-0/0/7 flexible-vlan-tagging
set interfaces ge-0/0/7 native-vlan-id 300
set interfaces ge-0/0/7 encapsulation extended-vlan-bridge
set interfaces ge-0/0/7 unit 100 vlan-id-list 200
set interfaces ge-0/0/7 unit 100 vlan-id-list 300
set interfaces ge-0/0/7 unit 100 input-vlan-map push
set interfaces ge-0/0/7 unit 100 output-vlan-map pop
set vlans VLAN100 interface ge-0/0/7.100
set vlans VLAN100 interface ge-0/0/6.100
 

The following pcap collected at NNI egressedn (i.e ge-0/0/6.100) illustrates such behavior change:

14.X53-D46 - Single Tag with S-VLAN

Ethernet II, Src: JuniperN_61:6c:41 (c0:42:d0:61:6c:41), Dst: JuniperN_2a:aa:41 (c0:42:d0:2a:aa:41)
802.1Q Virtual LAN, PRI: 0, DEI: 0, ID: 100 <-- S-VLAN 
Internet Protocol Version 4, Src: 192.168.3.100, Dst: 192.168.3.200
Internet Control Message Protocol


14.X53-D47 - Double Tag with S-VLAN and native-Vlan as Inner Vlan

Ethernet II, Src: JuniperN_61:6c:41 (c0:42:d0:61:6c:41), Dst: JuniperN_2a:aa:41 (c0:42:d0:2a:aa:41)
802.1Q Virtual LAN, PRI: 0, DEI: 0, ID: 100 <-- S-VLAN
802.1Q Virtual LAN, PRI: 0, DEI: 0, ID: 300 <-- Native-VLAN
Internet Protocol Version 4, Src: 192.168.3.100, Dst: 192.168.3.200
Internet Control Message Protocol

 

Solution

There is a behavior change in some EX and QFX switches to align with certain Juniper products (e.g. MX Platforms) and other vendors from single tag to double tag in S-VLAN.

In addition, a new CLI ( set interface XXX input-native-vlan-push enable/disable ) is available to change between single and double tag in S-VLAN from 19.3R1.

For details, refer to the technical documentation on input-native-vlan-push

Notes:

  • New CLI is made hidden in 18.1R3-S9/18.2R3/18.3R3/18.4R3/18.4R2-S3 and 19.1R2/19.2R2 (not supported officially by JTAC).
  • Contact your JTAC representative for a workaround if you need to change tagging behavior in a Junos release where the new CLI is not available

 

The tables below illustrate the default behavior for untagged traffic over S-VLAN.

  • S = Single Tag
  • D = Double Tag
  • *  = New CLI hidden
  • ** = New CLI NOT hidden 


Table 1: Behavior in 14.1X53 for various EX and QFX

 

Table 2: Behavior in QFX5K and EX4600/4650 from 17.1 to 19.3

Notes:

  • Table 2 is applicable to EX2300/EX3400 from 18.1 to 19.3
  • EX2300/EX3400 single tag is in all 15.1X53 up to 15.1X53-D592
  • Table 2 is applicable to EX4300-MP from 18.2 to 19.3


Table 3: Behavior in EX4300 from 17.1 to 19.3

Note: 17.3R4 changed from Single tag to Double tag with the fix of PR1413700 and it rollback to Single Tag with new CLI added.

As a reference, the following PRs are related to Q-in-Q Native VLAN behavior change in EX and QFX as in the above tables. 

 

Modification History

2020-03-02: Added 18.4R2-S3 to Junos OS release list in which new CLI is available

 

Related Information