Brocade Multi-Service IronWare Multiprotocol Label Switch (MPLS) Configuration Guide (Supporting R05.6.00) - Manual (Page 561)

Multi-Service IronWare Multiprotocol Label Switch (MPLS) Configuration Guide 537
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Configuring MPLS VLLs
4
NOTE
By removing FDP from the configuration, no fdp enable stays in the configuration of the VLPS
endpoints, which cannot be removed.
Special considerations for VLL dual-tagged endpoints
Before configuring a dual-tagged endpoint, consider the following:
• An Internal Forwarding Lookup Identifier (IFL-ID) is be allocated to each MPLS VLL instance that
has a dual-tagged endpoint. The ID is displayed in the show mpls vll detail command output.
For instances that do not have dual-tagged endpoints, the IFL-ID is be displayed as '--'.
• The tag protocol identifier (TPID) of the inner VLAN tag must be 0x8100 in order to be classified
as dual-tagged and recognized by dual-tagged endpoints. When the TPID is not 0x8100, the
packet is be classified as a single-tagged packet.
• The same port, outer VLAN, and inner VLAN combination cannot be specified across MPLS VLL
instances. For example, when a dual-tagged endpoint with vlan 100 and inner-vlan 200 is
configured on port e 2/1 in MPLS VLL instance 'test', the same endpoint cannot be configured
as part of another MPLS VLL instance, say 'test1'. This is also true across applications. That is,
when a port, outer VLAN, and inner VLAN combination belongs to a MPLS VLL instance, it
cannot simultaneously belong to a Layer 2 VLAN, Local VLL or VPLS.
• To change an existing single-tagged VLL endpoint to a dual-tagged endpoint, first delete the
VLAN configuration, then configure the endpoint as dual-tagged.
• A dual-tagged VLL endpoint neither recognizes nor forwards packets that have a single tag.
However, a single-tagged endpoint can recognize and forward dual-tagged packets because
the endpoint treats the second tag as data.
• The port, outer VLAN, and inner VLAN combination in an incoming dual- tagged packet on a
given port is used to do an IFL CAM lookup. This lookup yields an IFL-ID which is used to do a
MPLS-VLL CAM lookup. So for dual-tagged endpoints, the regular (port, vlan) lookup is replaced
with the (port, IFL-ID) lookup.
• When only the outer VLAN is specified for a given endpoint, it is called a less-specific VLAN.
When both the outer and inner VLAN are specified, it is called a more-specific VLAN (in relation
to the outer VLAN).
• When a less-specific VLAN is already configured on a given port, then a more-specific VLAN
with the same outer VLAN tag can also be configured on that port. Likewise, when a
more-specific VLAN is already configured on a given port, then a less-specific VLAN with the
same outer VLAN tag can also be configured on the port.
In the following example, a less-specific tagged endpoint has been configured with vlan 100 on
port e 2/1, and a more-specific VLAN with an outer VLAN tag of 100 and an inner vlan tag of
200 has also been configured on port e 2/1.
Brocade(config-mpls)# vll test1 1000
Brocade(config-mpls-vll-test1)# vlan 100
Brocade(config-mpls-vll-test1-vlan)# tag e 2/1
Brocade(config-mpls-vll-test1-if-e-2/1)# vll test2 2000
Brocade(config-mpls-vll-test2)# vlan 100 inner-vlan 200
Brocade(config-mpls-vll-test2-vlan)# tag e 2/1
This applies even when the less/more-specific VLAN is configured as part of a L2 VLAN, Local
VLL or VPLS.