Tagging

Mon, 14 Apr 2025 16:52:11 -0400

Junos VLAN Tagging Options Explained

Here’s a comparison of vlan-tagging, flexible-vlan-tagging, and encapsulation flexible-ethernet-services.

1. `vlan-tagging`

Configuration Level: Physical Interface (set interfaces <interface-name> vlan-tagging)
Purpose: Enables basic IEEE 802.1Q VLAN tagging support on the physical interface.
Capabilities:
- Allows logical units (unit) under this interface to be configured with a single VLAN ID (set interfaces <interface-name> unit <number> vlan-id <id>).
- Supports sending and receiving standard single-tagged Ethernet frames.
- Can support one untagged VLAN using the native-vlan-id option on the physical interface.
Limitations:
- Does not natively support receiving or sending double-tagged (QinQ/Stacked VLAN) frames on logical units.
- Does not easily support mixing tagged and untagged traffic across different logical units on the same physical interface (only one native/untagged VLAN is easily supported for the whole port).
- Limited flexibility in VLAN mapping per logical unit.
Typical Use Case:
- Standard “trunk” ports connecting to switches or other routers where multiple VLANs, each identified by a single tag, need to be carried.
- Simple Layer 2 or Layer 3 sub-interfaces.

Example:

junos

# Configure the physical interface for basic single-tagging
set interfaces ge-0/0/1 vlan-tagging
set interfaces ge-0/0/1 native-vlan-id 10  # Optional: VLAN 10 is untagged

# Configure logical units with single VLAN IDs
set interfaces ge-0/0/1 unit 100 vlan-id 100
set interfaces ge-0/0/1 unit 100 family inet address 192.168.100.1/24

set interfaces ge-0/0/1 unit 200 vlan-id 200
set interfaces ge-0/0/1 unit 200 family inet address 192.168.200.1/24

2. `flexible-vlan-tagging`

Configuration Level: Physical Interface (set interfaces <interface-name> flexible-vlan-tagging)
Purpose: Enables advanced VLAN tagging capabilities, allowing for more complex scenarios on a single physical interface.
Capabilities:
- Supports logical units with single VLAN IDs (vlan-id).
- Supports logical units with double (stacked/QinQ) VLAN tags (vlan-tags outer <tag> inner <tag>).
- Supports logical units accepting untagged traffic (vlan-id none, though configuration details vary slightly by platform/scenario).
- Allows mixing single-tagged, double-tagged, and untagged logical units on the same physical interface.
- Supports VLAN ID lists and ranges on logical units (vlan-id-list [ list-of-vlans ]).
- Often a prerequisite for advanced Layer 2 features and services.
Limitations:
- Slightly more complex configuration as each logical unit’s tagging requirement must be explicitly defined.
Typical Use Case:
- QinQ deployments (Service Provider NNI, Enterprise Campus).
- Interfaces needing to handle a mix of single-tagged customer traffic and double-tagged infrastructure traffic.
- Interfaces where some services are tagged and others are untagged.
- Aggregation points requiring flexible VLAN mapping.

Example:

junos

# Configure the physical interface for advanced tagging
set interfaces xe-0/1/0 flexible-vlan-tagging

# Configure a logical unit for single-tagged traffic
set interfaces xe-0/1/0 unit 101 description "Single Tagged Customer A"
set interfaces xe-0/1/0 unit 101 vlan-id 101
set interfaces xe-0/1/0 unit 101 family bridge # Example for L2

# Configure a logical unit for double-tagged (QinQ) traffic
set interfaces xe-0/1/0 unit 500 description "QinQ Customer B (Outer 500, Inner 50)"
set interfaces xe-0/1/0 unit 500 vlan-tags outer 500 inner 50
set interfaces xe-0/1/0 unit 500 family bridge # Example for L2

# Configure a logical unit for untagged traffic (config might vary slightly)
# This often requires specific encapsulation like vlan-bridge or ethenet-bridge
set interfaces xe-0/1/0 unit 0 description "Untagged Management"
set interfaces xe-0/1/0 unit 0 encapsulation vlan-bridge
# Note: No 'vlan-id' or 'vlan-tags' means it might handle untagged frames if configured correctly
set interfaces xe-0/1/0 unit 0 family inet address 10.0.0.1/24

# Configure a logical unit accepting a list of VLANs
set interfaces xe-0/1/0 unit 999 description "VLAN List Service"
set interfaces xe-0/1/0 unit 999 vlan-id-list [ 200 205-210 300 ]
set interfaces xe-0/1/0 unit 999 encapsulation vlan-bridge

3. `encapsulation flexible-ethernet-services`

Configuration Level: Physical Interface (set interfaces <interface-name> encapsulation flexible-ethernet-services)
Purpose: Primarily used on MX Series routers (and some other platforms) to allow a mix of different Layer 2 encapsulation types (like bridge, ccc, vpls) on different logical units of the same physical interface. It fundamentally changes how the interface PFE (Packet Forwarding Engine) processes frames to support this service flexibility.
Capabilities:
- Allows logical units (unit) under the same physical interface to have different Ethernet service encapsulations (e.g., encapsulation vlan-bridge, encapsulation vlan-ccc, encapsulation vlan-vpls, encapsulation ethernet-ccc, etc.).
- Enables maximum service multiplexing onto a single physical port.
Important Note: This option must often be used in conjunction with flexible-vlan-tagging if the services running on the logical units need to handle tagged frames (single or double). flexible-ethernet-services defines the service type flexibility, while flexible-vlan-tagging defines the VLAN tag flexibility.
Limitations:
- Platform-specific (mainly MX Series).
- Adds configuration complexity.
- Cannot be combined with vlan-tagging on the same physical interface.
Typical Use Case:
- Service Provider edge routers (PE) terminating multiple customers with different L2VPN service types (E-Line/CCC, E-LAN/VPLS, E-Tree) or bridging requirements on the same physical link (NNI or UNI).
- Data Center interconnects requiring diverse L2 service types.

Example:

junos

# Configure the physical interface for flexible service encapsulations AND flexible tagging
set interfaces xe-0/2/0 encapsulation flexible-ethernet-services
set interfaces xe-0/2/0 flexible-vlan-tagging

# Logical unit for a bridged service (single tag)
set interfaces xe-0/2/0 unit 1000 description "Bridged Service VLAN 1000"
set interfaces xe-0/2/0 unit 1000 encapsulation vlan-bridge
set interfaces xe-0/2/0 unit 1000 vlan-id 1000

# Logical unit for a VPLS service (QinQ tag)
set interfaces xe-0/2/0 unit 2000 description "VPLS Service Outer 200 Inner 20"
set interfaces xe-0/2/0 unit 2000 encapsulation vlan-vpls
set interfaces xe-0/2/0 unit 2000 vlan-tags outer 200 inner 20

# Logical unit for a CCC/L2Circuit service (single tag)
set interfaces xe-0/2/0 unit 3000 description "CCC/E-Line Service VLAN 3000"
set interfaces xe-0/2/0 unit 3000 encapsulation vlan-ccc
set interfaces xe-0/2/0 unit 3000 vlan-id 3000

Summary Table

Feature	`vlan-tagging`	`flexible-vlan-tagging`	`encapsulation flexible-ethernet-services` (+ `flexible-vlan-tagging`)
Config Level	Physical Interface	Physical Interface	Physical Interface
Primary Purpose	Basic 802.1Q tagging	Advanced VLAN tagging (QinQ, Mixed)	Mix different L2 service types on units
Single Tag Support	Yes (via `vlan-id` on unit)	Yes (via `vlan-id` on unit)	Yes (if `flexible-vlan-tagging` also used)
Double Tag (QinQ) Support	No	Yes (via `vlan-tags` on unit)	Yes (if `flexible-vlan-tagging` also used)
Untagged Support	Yes (one `native-vlan-id`)	Yes (per unit, requires specific config)	Yes (per unit, requires specific config)
Mixed Tag/Untagged Units	No (except native)	Yes	Yes
VLAN Lists/Ranges	No	Yes	Yes
Mixed L2 Encapsulations per Port	No	No	Yes (e.g., bridge, ccc, vpls on same port)
Common Platforms	All Junos platforms	Most modern Junos platforms	Primarily MX Series (and some others like PTX, ACX)
Use When…	Simple trunk port, single tags only.	Need QinQ, mix tagged/untagged, VLAN lists.	Need to mix L2VPN service types (VPLS, CCC, Bridge) on one port (MX).

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ngeran[io]

Tagging

Junos VLAN Tagging Options Explained

1. vlan-tagging

2. flexible-vlan-tagging

3. encapsulation flexible-ethernet-services

Summary Table

AS Path

Local Preference

BGP Attributes

Route Selection

Finite State Machine

Headers and Types

Type 5 - AS External

Type 4 - ASBR Summary

Type 3 - Summary

Type 2 - Network

Type 1 - Router

1. `vlan-tagging`

2. `flexible-vlan-tagging`

3. `encapsulation flexible-ethernet-services`