Cisco ASR 900 Series User Manual

Without any hop-limit, the best path from Router A to Router E as selected by PCALC is [A, C, D, E] since
this path has lower accumulated path cost than the other path [A, B, E]. If hop-limit is set to two, then the
best path that can pass this check is [A, B, E] even though it has higher accumulated path cost.
Figure 14: Topology: Hop Count and Path Cost
Flex LSP Cost-Max Limit
In some scenarios, accumulated path cost is used as an estimate for path delay between a source node and
destination node. The intent is to ensure that the accumulated path cost of a chosen path is not higher than a
configured limit. A cost limit check is added after the CSPF determines the best path (lowest cost path that
satisfied the path request constraints) from source node to destination node, and that for path verification.
Ensure that the accumulated path cost for co-routed bidirectional LSP includes both, forward and reverse
path cost.
Note
To configure the hop-limit that is applicable to a specific tunnel, use:
Router(config)# interface tunnel 1400
Router(config-if)# tunnel mpls traffic-eng path-selection cost-limit <1-4294967295>
Configuring Flex LSP Hop Count and Cost-Max Limit
Configure each end of the co-routed bi-directional LSP independently. Ensure that cost-limit and hop-limit
on both ends are configured in the same way.
Router(config)# interface tunnel 1000
Router(config-if)# ip unnumbered loopback0
Router(config-if)# tunnel mode mpls traffic-eng
Router(config-if)# tunnel destination 56.6.6.6
Router(config-if)# tunnel mpls traffic-eng bidir association type co-routed fault-oam wrap
Router(config-if)# tunnel mpls traffic-eng bidir association id 1000 source 55.5.5.5 global
1000
Router(config-if)# tunnel mpls traffic-eng path-selection hop-limit 5
Router(config-if)# tunnel mpls traffic-eng bandwidth 200
Router(config-if)# tunnel mpls traffic-eng autoroute announce
Router(config-if)# tunnel mpls traffic-eng path-option 10 dynamic
Router(config)# interface tunnel 3000
Router(config-if)# ip unnumbered loopback0
Router(config-if)# tunnel mode mpls traffic-eng
Router(config-if)# tunnel destination 56.6.6.6
Router(config-if)# tunnel mpls traffic-eng bidir association type co-routed fault-oam wrap
Router(config-if)# tunnel mpls traffic-eng bidir association id 3000 source 55.5.5.5 global
MPLS Basic Configuration Guide, Cisco IOS XE Everest 16.5.1 (Cisco ASR 900 Series)
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Flex LSP Overview
Flex LSP Hop Count and Cost-Max Limit

Cisco ASR 900 Series Specifications

General

Brand	Cisco
Model	ASR 900 Series
Category	Network Router
Language	English