The following policy parameters and validation rules apply to the MPLS forwarding policy and are enforced at configuration time:
A policy must have either the endpoint or the binding-label command to be valid or the no shutdown is not allowed. These commands are mutually exclusive per policy.
The endpoint command specifies that this policy is used for resolving the next hop of IPv4 or IPv6 packets, of BGP prefixes in GRT, of static routes in GRT, of VPRN IPv4 or IPv6 prefixes, or of service packets of EVPN prefixes. It is also used to resolve the next hop of BGP-LU routes.
The resolution of prefixes in these contexts matches the IPv4 or IPv6 next-hop address of the prefix against the address of the endpoint. The family of the primary and backup next hops of the NHGs within the policy are not relevant to the resolution of prefixes using the policy.
See Tunnel table handling of MPLS forwarding policy for information about CLI commands for binding these contexts to an endpoint policy.
The binding-label command allows the user to specify the label for binding to the policy such that labeled packets matching the ILM of the binding label can be forwarded over the NHG of the policy.
The ILM entry is created only when a label is configured. Only a provisioned binding label from a reserved label block is supported. The name of the reserved label block using the reserved-label-block command must be configured.
The payload of the packet forwarded using the ILM (payload underneath the swapped label) can be IPv4, IPv6, or MPLS. The family of the primary and backup next hops of the NHG within the policy are not relevant to the type of payload of the forwarded packets.
Changes to the values of the endpoint and binding-label parameters require a shutdown of the specific forwarding policy context.
A change to the name of the reserved-label-block requires a shutdown of the forwarding-policies context. The shutdown is not required if the user extends or shrinks the range of the reserved-label-block.
The preference parameter allows the user to configure multiple endpoint forwarding policies with the same endpoint address value or multiple label-binding policies with the same binding label; providing the capability to achieve a 1:N backup strategy for the forwarding policy. Only the most preferred, lowest numerical preference value, policy is activated in data path as described in Policy resolution and operational procedures.
Changes to the value of parameter preference requires a shutdown of the specific forwarding-policy context.
A maximum of eight label-binding policies, with different preference values, are allowed for each unique value of the binding label.
Label-binding policies with exactly the same value of the tuple {binding label | preference} are duplicate and their configuration is not allowed.
The user cannot perform no shutdown on the duplicate policy.
A maximum eight endpoint policies, with different preference values, are allowed for each unique value of the tuple {endpoint}.
Endpoint policies with exactly the same value of the tuple {endpoint, reference} are duplicate and their configuration is not allowed.
The user cannot perform no shutdown on the duplicate policy.
The metric parameter is supported with the endpoint policy only and is inherited by the routes which resolve their next hop to this policy.
The revert-timer command configures the time to wait before switching back the resolution from the backup next hop to the restored primary next hop within an NHG. By default, this timer is disabled meaning that the NHG immediately reverts to the primary next hop when it is restored.
The revert timer is restarted each time the primary next hop flaps and comes back up again while the previous timer is still running. If the revert timer value is changed while the timer is running, it is restarted with the new value.
The MPLS forwarding policy feature allows for a maximum of 32 NHGs consisting of, at most, one primary next hop and one backup next hop.
The next-hop command allows the user to specify a direct next-hop address or an indirect next-hop address.
A maximum of ten labels can be specified for a primary or backup direct next hop using the pushed-labels command. The label stack is programmed using a super-NHLFE directly on the outgoing interface of the direct primary or backup next hop.
The resolution-type {direct| indirect} command allows a limited validation at configuration time of the NHGs within a policy. The no shutdown command fails if any of these rules are not satisfied. The following are the rules of this validation:
NHGs within the same policy must be of the same resolution type.
A forwarding policy can have a single NHG of resolution type indirect with a primary next hop only or with both primary and backup next hops. An NHG with backup a next hop only is not allowed.
A forwarding policy has one or more NHGs of resolution type direct with a primary next hop only or with both primary and backup next hops. An NHG with a backup next hop only is not allowed.
A check is performed to make sure the address value of the primary and backup next hop, within the same NHG, are not duplicates. No check is performed for duplicate primary or backup next-hop addresses across NHGs.
A maximum of 64,000 forwarding policies of any combination of label binding and endpoint types can be configured on the system.
The IP address family of an endpoint policy is determined by the family of the endpoint parameter. It is populated in the TTMv4 or TTMv6 table accordingly. A label-binding policy does not have an IP address family associated with it and is programmed into the label (ILM) table.
The following are the IP type combinations for the primary and backup next hops of the NHGs of a policy:
A primary or a backup indirect next hop with no pushed labels (label-binding policy) can be IPv4 or IPv6. A mix of both IP types is allowed within the same NHG.
A primary or backup direct next hop with no pushed labels (label-binding policy) can be IP types IPv4 or IPv6. A mix of both families is allowed within the same NHG.
A primary or a backup direct next hop with pushed labels (both endpoint and label binding policies) can be IP types IPv4 or IPv6. A mix of both families is allowed within the same NHG.