Configuration Limits for Cisco NX-OS Layer 3 Unicast Features

Configuration limits for Cisco NX-OS layer 3 unicast features

The configuration limits for Cisco NX-OS layer 3 unicast features specify the maximum supported values for various configuration parameters. Limits are documented in the Cisco Nexus 9000 Series NX-OS Verified Scalability Guide.

For detailed configuration limits, refer to the official scalability guide.

Layer 3 heavy routing template

The Layer 3 Heavy Routing Template is a system routing profile that reallocates hardware resources to increase the maximum number of IPv4 and IPv6 unicast routes supported. It dedicates more hardware to efficient storage and lookup of Layer 3 prefixes using a routing trie structure.

  • Optimizes hardware for high-scale Layer 3 routing environments.

  • Enables greater route scale by increasing trie-based route storage.

Use cases and benefits

This template is intended for situations where a large volume of IPv4 and IPv6 routes must be supported, such as:

  • Data center or cloud deployments with extensive routing requirements.

  • Environments where the default routing profile does not provide adequate route capacity.

Guidelines and limitations for layer 3 heavy routing template

Use the Layer 3 Heavy Routing Template only on supported cloud-scale hardware. The template is not compatible with platforms outside the supported list and may impact available hardware resources for other features.

  • You can configure the Layer 3 Heavy Routing Template on FX, FX2, FX3, GX, GX2, and HX cloud-scale Cisco Nexus 9000 switches.

  • Layer 3 Heavy Routing Template is not supported on other cloud-scale TOR or EOR platforms.

  • Template changes take effect only after saving the configuration and reloading the switch.

  • Enabling this template reallocates hardware tiles to maximize route scale, which may reduce resources available for less-used features.

  • Increased hardware allocation for Layer 3 routing may result in higher memory consumption.

Layer 3 heavy routing template scale limits

This section lists scale limits and technical specifications for the Layer 3 Heavy Routing Template compared to the default routing template, as provided in the engineering documentation.

The following table lists:

  • Resource (entries): The hardware resource or route type being measured.

  • Default Template: Maximum value supported with the default routing template.

  • Layer 3 Heavy Template: Maximum value supported with the Layer 3 Heavy Routing Template.

Table 1. Layer 3 heavy routing template vs. default template: scale limits

Resource

Default Template

Layer 3 Heavy Template

Max IPv4 Trie route entries

1,048,576

1,256,448

Max IPv6 Trie route entries

589,824

628,224

Max TCAM table entries

24,576

24,576

Max V4 Ucast TCAM table entries

16,384

16,384

Max V6 Ucast TCAM table entries

2,048

2,048

Max native host route entries (shared v4/v6)

196,608

65,536

Max Nexthop table entries

98,304

98,304

Max ARP entries

98,304

65,536

Max ND entries

98,304

32,768

Configure the layer 3 heavy routing template

This task allows you to change the system routing profile to maximize Layer 3 route scale using the Layer 3 Heavy Routing Template.

  • Support larger IPv4 and IPv6 routing tables in hardware.

  • Resolve route scale limitations due to default hardware resource allocation.

Use this procedure if your network requires greater Layer 3 route capacity than the default system routing template provides.

Before you begin

Ensure the following before performing this task:

  • Save your current configuration and schedule a maintenance window to reload the switch.

  • Review the memory and resource impact before enabling this feature.

Procedure

Step 1

Use the system routing template-l3-heavy command to apply the Layer 3 Heavy Routing Template.

Example:

switch(config)# system routing template-l3-heavy

This command applies the Layer 3 Heavy Routing Template and increases the hardware allocation for route storage.

Note

 

You must save the configuration and reload the switch for the change to take effect.

The system is configured to use the Layer 3 Heavy Routing Template after the next reload.

Step 2

Use the copy running-config startup-config command to save the configuration.

Example:

switch(config)# copy running-config startup-config

This ensures your new template configuration persists across a reload.

Configuration is saved to startup-config.

Step 3

Use the reload command to reload the switch.

Example:

switch# reload

The switch must be reloaded for the new routing template to take effect.

Layer 3 Heavy Routing Template becomes active after reload.

What to do next

After completing the configuration, verify that the Layer 3 Heavy Routing Template is active and functioning as expected.

See Verify Layer 3 Heavy Routing Template for verification steps.

Verify layer 3 heavy routing template

This verification ensures the Layer 3 Heavy Routing Template is correctly applied and that the system is operating in the intended routing mode. Validate that hardware resources are allocated to maximize Layer 3 route scale.

After enabling the Layer 3 Heavy Routing Template and reloading the switch, use these steps to verify that the configuration is active and functioning as expected.

Before you begin

Before starting verification, make sure the Layer 3 Heavy Routing Template is configured and the switch has been reloaded to apply the changes.

Procedure

Step 1

Use the show system routing mode command to check the system routing mode configuration and applied state.

Example:


            switch# 
            show system routing mode
            Configured System Routing Mode: L3 Heavy
            Applied System Routing Mode: L3 Heavy

The command output should display Configured System Routing Mode: L3 Heavy and Applied System Routing Mode: L3 Heavy .

The system confirms that the Layer 3 Heavy Routing Template is both configured and applied.

Step 2

Use the show hardware internal forwarding table utilization module 1 command to verify hardware forwarding table resource allocation.

Example:


            switch# 
            show hardware internal forwarding table utilization module 1
            IPv4/IPv6 hosts and routes summary on module : 1
            --------------------------------------------------
            Configured System Routing Mode: NX_L3_Heavy
            Max IPv4 Trie route entries: 1153433
            Max IPv6 Trie route entries: 628224

Check that the Configured System Routing Mode" is "NX_L3_Heavy and review the maximum values for IPv4 and IPv6 trie route entries, TCAM table entries, and other relevant hardware resource limits.

Values should match the expected scale for the Layer 3 Heavy Routing Template.

Hardware resources have been reallocated to support increased Layer 3 route scale.

Step 3

(Optional) Use the show hardware internal tah logical-tile-types command to verify logical tile allocation details.

Example:


            switch# 
            show hardware internal tah logical-tile-types
            Logical Tile Types
            Instance : 0
            Profile: L3 Heavy Scale
            FPX: 0 Tile: 0 Tile-depth: 8192 type_tile_id: 0/0 lo: 0x0 col: 1 offset: 0x0 TT: IP Log.TT: IP DS:Hash table TP:Left tilepair v4/v6: 0/0 htype: 0

This command provides advanced detail on how hardware tiles are allocated to different functions under the active routing template.

Logical tile allocation reflects the Layer 3 Heavy Routing Template settings.

The switch is confirmed to be operating with the Layer 3 Heavy Routing Template and supporting the intended route scale and hardware allocation.