An endpoint forwarding policy once validated as the most preferred policy for given endpoint address is added to the TTMv4 or TTMv6 according to the address family of the address of the endpoint parameter. A new owner of mpls-fwd-policy is used. A tunnel ID is allocated to each policy and is added into the TTM entry for the policy. For more information about the mpls-fwd-policy command, used to enable MPLS forwarding policy in different services, refer to the following guides:
7450 ESS, 7750 SR, 7950 XRS, and VSR Layer 2 Services and EVPN Guide: VLL, VPLS, PBB, and EVPN
7450 ESS, 7750 SR, 7950 XRS, and VSR Layer 3 Services Guide: IES and VPRN
7450 ESS, 7750 SR, 7950 XRS, and VSR Router Configuration Guide
7450 ESS, 7750 SR, 7950 XRS, and VSR Unicast Routing Protocols Guide
The TTM preference value of a forwarding policy is configurable using the parameter tunnel-table-pref. The default value of this parameter is 255.
Each individual endpoint forwarding policy can also be assigned a preference value using the preference command with a default value of 255. When the forwarding policy database compares multiple forwarding policies with the same endpoint address, the policy with the lowest numerical preference value is activated and programmed into TTM. The TTM preference assigned to the policy is its own configured value in the tunnel-table-pref parameter.
If an active forwarding policy preference has the same value as another tunnel type for the same destination in TTM, then routes and services which are bound to both types of tunnels use the default TTM preference for the two tunnel types to select the tunnel to bind to as shown in Table 1.
Route Preference |
Value |
Release Introduced |
|---|---|---|
ROUTE_PREF_RIB_API |
3 |
new in 16.0.R4 for RIB API IPv4 and IPv6 tunnel table entry |
ROUTE_PREF_MPLS_FWD_POLICY |
4 |
new in 16.0.R4 for MPLS forwarding policy of endpoint type |
ROUTE_PREF_RSVP |
7 |
— |
ROUTE_PREF_SR_TE |
8 |
new in 14.0 |
ROUTE_PREF_LDP |
9 |
— |
ROUTE_PREF_OSPF_TTM |
10 |
new in 13.0.R1 |
ROUTE_PREF_ISIS_TTM |
11 |
new in 13.0.R1 |
ROUTE_PREF_BGP_TTM |
12 |
modified in 13.0.R1 (pref was 10 in R12) |
ROUTE_PREF_UDP |
254 |
introduced with 15.0 MPLS-over-UDP tunnels |
ROUTE_PREF_GRE |
255 |
— |
An active endpoint forwarding policy populates the highest pushed label stack size among all its NHGs in the TTM. Each service and shortcut application on the router will use that value and perform a check of the resulting net label stack by counting all the additional labels required for forwarding the packet in that context.
This check is similar to the one performed for SR-TE LSP and SR policy features. If the check succeeds, the service is bound or the prefix is resolved to the forwarding policy. If the check fails, the service will not bind to this forwarding policy. Instead, it will bind to a tunnel of a different type if the user configured the use of other tunnel types. Otherwise, the service will go down. Similarly, the prefix will not get resolved to the forwarding policy and will either be resolved to another tunnel type or will become unresolved.
For more information about the resolution-filter CLI commands for resolving the next hop of prefixes in GRT, VPRN, and EVPN MPLS into an endpoint forwarding policy, refer to the following guides:
7450 ESS, 7750 SR, 7950 XRS, and VSR Layer 2 Services and EVPN Guide: VLL, VPLS, PBB, and EVPN
7450 ESS, 7750 SR, 7950 XRS, and VSR Layer 3 Services Guide: IES and VPRN
7450 ESS, 7750 SR, 7950 XRS, and VSR Router Configuration Guide
7450 ESS, 7750 SR, 7950 XRS, and VSR Unicast Routing Protocols Guide
BGP-LU routes can also have their next hop resolved to an endpoint forwarding policy.