maximum-paths [n]
Configures the maximum number of equal-cost paths that OSPF can install in the routing table for a single destination, enabling load balancing across multiple links.
maximum-paths [n]When to Use This Command
- Load balance traffic across two equal-cost OSPF links between routers to increase bandwidth utilization.
- Configure a maximum of 4 paths in a redundant OSPF network with multiple parallel links to ensure efficient load sharing.
- Limit the number of paths to 1 to force OSPF to use only the best path, simplifying troubleshooting or meeting specific policy requirements.
- Increase the maximum paths from default (4) to 8 on high-end routers supporting more ECMP paths for better load distribution.
Command Examples
Set maximum paths to 2 for load balancing
maximum-paths 2Router(config-router)# maximum-paths 2
Router(config-router)# end
Router# show ip route ospf
10.1.1.0/24 is variably subnetted, 2 subnets, 2 masks
O 10.1.1.0/24 [110/2] via 192.168.1.1, 00:00:12, GigabitEthernet0/0
[110/2] via 192.168.2.1, 00:00:12, GigabitEthernet0/1The command sets OSPF to use up to 2 equal-cost paths. The 'show ip route ospf' output displays two next-hop entries for the same destination (10.1.1.0/24), each with the same metric (110/2), indicating load balancing across two interfaces.
Reset to default maximum paths (4)
no maximum-pathsRouter(config-router)# no maximum-paths Router(config-router)# end Router# show ip protocols | include maximum Maximum path: 4
The 'no maximum-paths' command resets the value to the default (4). The 'show ip protocols' output confirms the maximum path count is 4.
Understanding the Output
The command itself does not produce output; its effect is seen in the routing table. Use 'show ip route' to see multiple next-hop entries for the same destination when ECMP is active. Each entry shows the OSPF-learned route with the administrative distance (110) and metric (cost). The presence of multiple lines for the same network indicates load balancing. A single entry means only one path is used (either because only one exists or maximum-paths is set to 1). The metric must be equal for paths to be considered equal-cost. If paths have different metrics, only the best (lowest metric) is installed regardless of the maximum-paths setting.
CCNA Exam Tips
CCNA exam tip: The default maximum-paths for OSPF is 4, but the exam may ask about the range (1 to 16) or the default (4).
CCNA exam tip: ECMP requires equal cost; OSPF cost is based on bandwidth (reference bandwidth / interface bandwidth). Ensure paths have identical costs for load balancing.
CCNA exam tip: The 'maximum-paths' command is configured in router configuration mode for OSPF, not interface mode.
CCNA exam tip: A common exam scenario: you see multiple routes for the same network in the routing table; the question may ask why or how to limit them.
Common Mistakes
Mistake 1: Setting maximum-paths to a value higher than the number of equal-cost paths available; no effect and no error.
Mistake 2: Forgetting that OSPF must have equal-cost paths; if costs differ, only one path is used even if maximum-paths is high.
Mistake 3: Applying the command in global configuration mode instead of router configuration mode (e.g., 'router ospf 1').
Related Commands
show ip ospf interface
Displays OSPF interface parameters and status, used to verify OSPF configuration and troubleshoot neighbor relationships.
show ip protocols
Displays the current state of all IP routing protocols running on the router, including timers, filters, and network advertisements.
show ip route
Displays the current IP routing table on a Cisco router, used to verify routes, check next-hop addresses, and troubleshoot connectivity issues.
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