MPLS RSVP Entropy Label Capabilities
To share the load across multiple members of a LAG port in the core of an MPLS network we can use entropy labels
An Entropy Label is always preceded by an Entropy level indicator which is a special Label with value seven, and indicates the next label present is an Entropy label. The trade off is the MPLS stack depth increases by two and it reduces overhead on transit routers.
Note: Load balancing is enabled by default for all the parameters. If you enable load balancing manually, then all the parameters enabled by default are reset and you need to enable the parameters based on which traffic should be load balanced.
Entropy labels will only be added when the remote edge node advertises its capability for Entropy.
The examples below show how entropy can be enabled on a provider edge node as per the setup we need to enable on RTR29 and RTR30 to have entropy enabled in both directions:
(config)#router rsvp
(config-router)#entropy-label-capability
This enables ELC signaling for RSVP.
For validation, use:
#show mpls forwarding-table
Codes: > - installed FTN, * - selected FTN, p - stale FTN, B - BGP FTN, K - CLI FTN, t - tunnel
L - LDP FTN, R - RSVP-TE FTN, S - SNMP FTN, I - IGP-Shortcut,
U - unknown FTN, O - SR-OSPF FTN, i - SR-ISIS FTN, k - SR-CLI FTN
Code FEC FTN-ID Tunnel-id Pri LSP-Type Out- Label ELC Out-Intf Nexthop
R(t)> 2 9.29.29.29/32 1 5001 Yes LSP_DEFAULT 24322 yes
xe2 1.41.41.31
R(t)> 29.29.29.29/32 2 5001 No LSP_DEFAULT 4322 yes
xe1 69.69.69.42
#show rsvp session ingress detail
Ingress (Primary)
41.41.41.31
From: 29.29.29.29, LSPstate: Up, LSPname: t1-Primary
Ingress FSM state: Operational
Establishment Time: 0s 3ms
Setup priority: 7, Hold priority: 0
CSPF usage: Enabled, CSPF Retry Count: 0, CSPF Retry Interval: 30 seconds
IGP-Shortcut: Disabled, LSP metric: 1
LSP Protection: None
Label in: -, Label out: 24320, ELC
Last modified date: 10/17/2023