Virtual Private LAN Services
7750 SR OS Services Guide Page 495
Use of Pseudowire Template for BGP VPLS
The pseudowire template concept used for BGP AD is re-used also for BGP VPLS to dynamically
instantiate pseudowire (SDP-bindings) and the related SDP (provisioned or automatically
instantiated).
On transmission the settings for the L2-Info extended community in the BGP Update are derived
from the pseudowire-template attributes. The following rules apply:
• If multiple pseudowire-templates (with or without import-rt) are specified for the same
VPLS instance the first pseudowire-template entry will be used.
• Encaps Type is always 19 (13 in hex)
→ BGP VPLS supports only the Ethernet pseudowire type so the setting of vc-type
parameter in pseudowire-template is ignored and ether value is always used.
• Layer 2 MTU – derived from service vpls service-mtu parameter
→ same value must be used in all related BGP VPLS instances in the Remote PEs to
ensure the related pseudowires will come up
→ in order to interoperate with existing implementations if the received MTU value = 0,
then MTU negotiation does not take place; the related pseudowire is setup ignoring
the MTU.
• Control Flag C – depending on the control-word setting in pseudowire-template
• Control Flag S – always 0
On reception the values of the parameters in the L2-Info extended community of the BGP Update
are compared with the settings from the corresponding pseudowire-template. The following steps
are used to determine the local pseudowire-template:
• The RT values are matched to determine the pseudowire-template.
• If multiple pseudowire-templates matches are found from the previous steps, the first
configured pseudowire-template entry will be considered.
• Note that it is expected that for most of the BGP VPLS use cases there will be no cases
where multiple RTs will be matched at the receiving end.
• If the values used for Layer 2 MTU or C Flag do not match the pseudowire setup fails.
The tools perform commands can be used similarly as for BGP-AD to force the application of
changes in pseudowire-template using the format described below:
tools perform service [id service-id] eval-pw-template policy-id [allow-service-impact]
This command is as follows:
To Next Page
Loading...
