When the hash-label option is enabled in a service context, hash label is always inserted at the bottom of the stack as per RFC 6391.
The LSR adds the capability to check a maximum of 16 labels in a stack. The LSR is able to hash on the IP headers when the payload below the label stack of maximum size of 16 is IPv4 or IPv6, including when a MAC header precedes it (eth-encap-ip option).
The Entropy Label (EL) feature, as specified in RFC 6790, is supported on RSVP, LDP, segment-routed, and BGP transport tunnels. It uses the Entropy Label Indicator (ELI) to indicate the presence of the entropy label in the label stack. The ELI, followed by the actual entropy label, is inserted immediately below the transport label for which entropy label feature is enabled. If multiple transport tunnels have the entropy label feature enabled, the ELI/EL is inserted below the lowest transport label in the stack.
The LSR hashing operates as follows:
If the lbl-only hashing option is enabled, or if one of the other LSR hashing options is enabled but a IPv4 or IPv6 header is not detected below the bottom of the label stack, the LSR hashes on the EL only.
If the lbl-ip option is enabled, the LSR hashes on the EL and the IP headers.
If the ip-only or eth-encap-ip is enabled, the LSR hashes on the IP headers only.
For more information about the Hash Label and Entropy Label features, see the ‟MPLS Entropy Label and Hash Label” section of the 7450 ESS, 7750 SR, 7950 XRS, and VSR MPLS Guide.