Brocade Multi-Service IronWare Multiprotocol Label Switch (MPLS) Configuration Guide (Supporting R05.6.00) - Manual (Page 512)

488 Multi-Service IronWare Multiprotocol Label Switch (MPLS) Configuration Guide
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Flooding Layer 2 BPDUs with a VPLS instance
3
Specifying a VPLS MTU
The vpls-mtu command allows the user to specify an MTU value per VPLS instance. The newly
configured VPLS MTU takes effect immediately to refresh or re-establish the VPLS sessions with
peers in the following manner:
• When the VPLS session is Operational and the VPLSs MTU is changed by configuration, bring
down the peer, send a label withdraw message to the peer, followed by the current VC binding
message.
• When the VPLS session is not Operational and the VPLS's MTU is changed by configuration and
the current state of the peer is VC-Parameter-MTU-Mismatch, the peer is brought UP when the
MTU is equal, and a VC withdraw message is sent to clean up the old binding on the peer, and
then a VC binding message is sent with the newly configured MTU. When the current state of
the peer is anything other than VC-Parameter-MTU-Mismatch, the VPLS's configured MTU is
changed.
• When a VC binding is received from a peer and VPLS MTU enforcement is enabled, the
received MTU is compared with the VPLS's MTU. When they are not equal, the peer is kept in
the VC-Parameter-MTU-Mismatch state, and otherwise made Operational. When the MTU
enforcement is disabled, the peer's MTU is saved and the peer is made Operational
irrespective of the MTU values.
To configure a new MTU value for a VPLS instance, use the vpls-mtu command as shown in the
following example.
Brocade(config-mpls)# vpls myvpls 40000
Brocade(config-mpls-vpls-myvpls)# vpls-mtu 1000
Syntax: [no] vpls-mtu mtu-value
The mtu-value variable can be set to any value between 64 through 9190.
When the user employs the [no] parameter to remove the configured MTU value for a VPLS
instance, that instance’s MTU becomes one of two possible values:
• When a global default MTU has been configured, then the MTU for this VPLS instance becomes
that global maximum frame size minus 26.
• When no global default exists, the MTU is 1500.
For example, when the user removes the MTU value for the VPLS named myvpls, and the global
default maximum frame size is 5000, then the MTU for VPLS myvpls becomes 4974 (5000 – 26 =
4974).
NOTE
This MTU parameter is not enforced on the data plane (hardware). Consequently, packets larger
than the configured MTU can still be sent or received.