This feature introduces the hardware forwarding support for IPv4 over IPv4, GRE-Tunnel interfaces on Arista Switches. A GRE-Tunnel interface acts as a logical interface which performs the GRE encapsulation or decapsulation. IPv6 payload over IPv4 GRE-Tunnel interfaces is supported with limitations (see Limitation section).

The TCP MSS clamping feature involves clamping the maximum segment size (MSS) in the TCP header of TCP SYN packets if it exceeds the configured MSS ceiling limit for the interface. Clamping MSS value helps in avoiding IP fragmentation in tunnel scenarios by ensuring that MSS is small enough to accommodate the extra overhead of GRE and tunnel outer IP headers. One of the most common use cases for this feature is connectivity towards Cloud providers via GRE which require asymmetric routing (for example DDoS protection).

RSVP-TE applies the Resource Reservation Protocol (RSVP) for Traffic Engineering (TE), i.e., to distribute MPLS labels for steering traffic and reserving bandwidth.