The allow-fragmentation command enables GRE SDP tunnel fragmentation and can be configured under the following:
SDP with type GRE (MPLS is not supported)
PW template with auto-gre-sdp
The services that are supported with GRE SDP fragmentation and reassembly include the following:
Epipe VLL services using GRE SDP tunnels
BGP-VPLS
BGP-VPWS
When enabled, GRE SDP tunnel fragmentation is applied to any generated GRE SDP tunnel packet where its size is greater than the MTU of the network interface needed to egress the node. The network interface chosen to egress the node is based on the SDP bindings for the service.
For GRE SDPs and SDP bindings using PW templates with auto-gre-sdp, if a received SAP packet size is greater than the service MTU, the packet is dropped per normal SAP ingress processing.
If GRE-SDP tunnel fragmentation is enabled when configuring allow-fragmentation, the DF-bit is cleared for unfragmented and fragmented GRE SDP tunnel packets. This allows downstream routers to fragment the packets further if needed.