The MPLS pseudowire hash label allows LSR nodes in a network to load balance labeled packets in a much more granular fashion than allowed by simply hashing on the standard label stack. It also removes the need to have an LSR inspect the payload below the label stack to check for an IPv4 or IPv6 header.
An MPLS hash label, is inserted by the ingress LER at the bottom of the label stack in packets forwarded over an LSP. The value of the label is the result of the hash of the packet headers (the packet header fields used depends on the capability of the ingress LER node). Since the ingress LER hash routine maintains packet ordering within a conversation, this guarantees that the spraying of packets by an LSR hashing on the extended label stack, which includes the hash label, will also maintain packet ordering within a conversation. LSR hashing pertains to multiple LDP ECMP paths or multiple paths over a LAG network port.
On 7210 SAS devices, the ingress node does not use the pseudowire hash label for ECMP hashing and LAG hashing. It is only available for use by the transit MPLS LSR nodes. See the 7210 SAS-Mxp, R6, R12, S, Sx, T Interface Configuration Guide for information about the fields used by the ingress LER for ECMP and LAG hashing.
The pseudowire hash label is supported for VLL with spoke SDP, and VPLS services with spoke SDP and mesh SDP.
This feature is only supported on the 7210 SAS-Mxp, 7210 SAS-Sx/S 1/10GE, 7210 SAS-R6 (IMMv2 cards), and 7210 SAS-R12 (IMMv2 cards).