Junos® OS Ethernet Interfaces Configuration ... - Juniper Networks

• For more information about binding a VLAN ID to the logical interface, see 802.1Q
VLANs Overview on page 53.
• For more information about the swap operation, see Examples: Stacking and Rewriting
Gigabit Ethernet IQ VLAN Tags on page 147.
• Junos® OS Ethernet Interfaces
Rewriting a VLAN Tag on Untagged Frames
Copyright © 2012, Juniper Networks, Inc.
On M320, M120, and MX Series routers with Gigabit Ethernet IQ, IQ2, and IQ2E PICs,
10-Gigabit Ethernet IQ, IQ2, and IQ2E PICs, and on MX Series 40-port Gigabit Ethernet
R, 40-port Gigabit Ethernet R EQ, 4-port 10-Gigabit Ethernet R, and 4-port 10-Gigabit
Ethernet R EQ DPCs, you can rewrite VLAN tags on untagged incoming and outgoing
frames under ethernet-ccc and ethernet-vpls encapsulations. On MX Series routers with
IQ2 and IQ2-E PICs, you can perform all rewrite VLAN tag operations. These features
provide added flexibility.
Consider a network where two provider edges (PE) are connected by a Layer 2 circuit.
PE1 is receiving traffic on an untagged port while the corresponding port on PE2 is tagged.
In the normal case, packets coming from PE1 will be dropped at PE2 because it is expecting
tagged packets. However, if PE1 can push a VLAN tag on the incoming packet before
sending it across to PE2, you can ensure that packets are not dropped. To make it work
in both directions, PE1 must strip the VLAN tag from outgoing packets. Therefore, a push
on the ingress side is always paired with a pop on the egress side.
The rewrite operations represented by the following statement options are supported
under ethernet-ccc and ethernet-vpls encapsulations:
• push—A VLAN tag is added to the incoming untagged frame.
• pop—VLAN tag is removed from the outgoing frame.
• push-push—An outer and inner VLAN tag are added to the incoming untagged frame.
• pop-pop—Both the outer and inner VLAN tags of the outgoing frame are removed.
IQ2 and 10-Gigabit Ethernet PICs support all rewrite operations described above. Details
on the possible combinations of usage are explained later in this section.
NOTE: The push-push and pop-pop operations are not supported on the
Gigabit Ethernet IQ PIC.
For the input-vlan-map statement, only the push and push-push options are supported
because it does not make sense to remove a VLAN tag from an incoming untagged frame.
Similarly, only the pop and pop-pop options are supported for the output-vlan-map
statement. Also, with the push and push-push options, the tag parameters have to be
explicitly specified. Apart from this, the other rules for configuring the input-vlan-map
and output-vlan-map statements are the same as for tagged frames. Table 12 on page 144
through Table 14 on page 144 explain the rules in more detail.
Chapter 5: Stacking and Rewriting Gigabit Ethernet VLAN Tags
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