Cisco NCS 5500 Series

Resilient Per-CE Label Allocation Mode
The Resilient Per-CE Label Allocation is an extension of the Per-CE label allocation mode to support Prefix
Independent Convergence (PIC) and load balancing. At present, the three label allocation modes, Per-Prefix,
Per-CE, and Per-VRF have these restrictions:
•
No support for ASR 9000 Ethernet Line Card and A9K-SIP-700
•
No support for PIC
•
No support for load balancing across CEs
•
Temporary forwarding loop during local traffic diversion to support PIC
•
No support for EIBGP multipath load balancing
•
Forwarding performance impact
•
Per-prefix label allocation mode causes scale issues on another vendor router in a network
In the Resilient Per-CE label allocation scheme, BGP installs a unique rewrite label in LSD for every unique
set of CE paths or next hops. There may be one or more prefixes in BGP table that points to this label. BGP
also installs the CE paths (primary) and optionally a backup PE path into RIB. FIB learns about the label
rewrite information from LSD and the IP paths from RIB. In steady state, labeled traffic destined to the resilient
per-CE label is load balanced across all the CE next hops. When all the CE paths fail, any traffic destined to
that label will result in an IP lookup and will be forwarded towards the backup PE path, if available. This
action is performed on the label independently of the number of prefixes that may point to the label, resulting
in the PIC behavior during primary paths failure.
Configure Resilient Per-CE Label Allocation Mode Under VRF Address Family
Perform this task to configure resilient per-ce label allocation mode under VRF address family.
SUMMARY STEPS
1.
configure
2.
router bgpas-number
3.
vrfvrf-instance
4.
address-family {ipv4 | ipv6} unicast
5.
label-mode per-ce
6.
Do one of the following:
•
end
•
commit
DETAILED STEPS
Step 1
configure
BGP Configuration Guide for Cisco NCS 5500 Series Routers, IOS XR Release 6.2.x
96
Implementing BGP
Resilient Per-CE Label Allocation Mode