LSR hashing operates on the label stack and can also include hashing on the IP header if the packet is an IPv4 packet. The label-IP hashing algorithm can also include the Layer 4 header and the TEID field. The default hash is on the label stack only. IPv4 is the only IP hashing supported on a 7705 SAR LSR.
When a 7705 SAR is acting as an LSR, it considers a packet to be IP if the first nibble following the bottom of the label stack is 4 (IPv4). This allows the user to include an IP header in the hashing routine at an LSR in order to spray labeled IP packets over multiple equal-cost paths in ECMP in an LDP LSP and/or over multiple links of a LAG group in all types of LSPs.
Other LSR hashing options include label stack profile options on the significance of the bottom-of-stack label (VC label), the inclusion or exclusion of the ingress port, and the inclusion or exclusion of the system IP address.
The global IF index is no longer a hash input for LSR ECMP load balancing. It has been replaced with the use-ingress-port configurable option in the lsr-load-balancing command. As well, the default treatment of the MPLS label stack has changed to focus on the bottom-of-stack label (VC label). In previous releases, all labels had equal influence.
LSR load balancing is configured using the config>system>lsr-load-balancing or config>router>if>load-balancing>lsr-load-balancing command. Configuration at the router interface level overrides the system-level configuration for the specified interface.
If an ELI is found in the label stack, the entropy label is used as the hash result. Hashing continues based on the configuration of label-only (lbl-only), label-IP (lbl-ip), or label-IP with Layer 4 header and TEID (lbl-ip-l4-teid) options.