Interfaces and Hardware Component Configuration Guide for Cisco 8000 Series Routers, Cisco IOS XR Releases

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Interfaces and Hardware Component Configuration Guide for Cisco 8000 Series Routers, Cisco IOS XR Releases

Network Virtualization using Generic Routing Encapsulation hash field selections

Updated: July 31, 2026

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This topic describes Network Virtualization using Generic Routing Encapsulation (NVGRE) hash field selections on the Cisco 8000 Series Router, which control whether NVGRE inner payload fields are included in the load-balancing hash calculation on Cisco Silicon One Q100 and Q200 ASIC-based systems.

Network Virtualization using Generic Routing Encapsulation (NVGRE) hash field selections are load-balancing configuration options that

  • provide the ability to control whether NVGRE inner payload fields are included in the hash calculation, and

  • configure hash field selection to consider only the outer headers, ensuring deterministic load distribution when the NVGRE payload is non-IP.

Benefits of NVGRE hash field selections

These are the benefits of NVGRE hash field selections:

  • Balances NVGRE traffic load across Equal Cost Multipath (ECMP) and Link Aggregation Group (LAG) paths.

  • Reduces traffic congestion and bottlenecks in virtualized network environments.

  • Enhances network efficiency by using inner Ethernet frame information for hashing.

Configuration guidelines for NVGRE hash field selection

These guidelines apply for configuring NVGRE hash field selection:

  • Use the GRE payload fields, including inner Ethernet frame source and destination MAC addresses, for hash computation.

  • Supported only on Cisco Silicon One Q100 and Q200 ASIC-based systems.

  • Use the feature to distribute NVGRE traffic across multiple physical paths for better resource utilization.

Restrictions for NVGRE hash field selection

These restrictions apply to NVGRE hash field selection:

  • It does not support outer IPv4 headers that contain options.

  • It does not support outer IPv6 headers with extension headers.

How NVGRE hash field selection works

Summary

NVGRE hash field selection works by allowing configurable hash field selection, ensuring predictable load distribution for NVGRE traffic across network links.

The key components involved in the NVGRE hash field selection process are:

  • ASIC (Q100/Q200): Performs packet inspection and hash calculation as directed by configuration.

  • Network administrator: Chooses the hash field mode to optimize NVGRE deployment outcomes.

  • Forwarding engine: Uses the calculated hash to make load-balancing decisions for NVGRE traffic.

Workflow

These stages describe how a router with a Cisco Silicon One Q100 or Q200 ASIC-based system processes NVGRE traffic and selects header fields for load-balancing hash calculations:

  1. The router receives an incoming packet and determines whether it is an NVGRE-encapsulated packet by checking the protocol value.
    • Packet arrives at the device ingress interface.
    • ASIC inspects the protocol value for 0x6558 (NVGRE).
    This identification is necessary to apply the NVGRE-specific hash field selection logic. Once the NVGRE packet is detected, the device prepares the hash selection procedure as configured for NVGRE traffic.
  2. The ASIC checks the device configuration to determine which headers should be used for hash calculation on NVGRE packets.
    • Device configuration is queried for the presence of cef platform load-balancing nvgre payload exclude.
    Configuration specifies whether only the NVGRE outer header or both outer and inner headers will participate in hashing. This is a static setting, chosen for deployment needs. No hash calculation occurs until the mode is identified.
  3. The ASIC performs the hash calculation according to the selected mode:
    • If nvgre payload exclude is enabled: Only the outer header fields (such as source and destination IP) are included in the hash.
    • If nvgre payload exclude is disabled (default): Both outer and inner header fields (including inner MAC or IP) are included.
    This stage determines load-balancing accuracy, especially when handling non-IP payloads.
  4. The forwarding engine applies the computed hash to select the egress path for the packet.
    • Hash value is used by ECMP or port-channel logic to assign the packet to a specific link.
    The outcome is consistent forwarding of NVGRE flows according to deployment requirements and traffic type. Traffic forwarding completes based on the device's hash selection, ensuring predictable NVGRE load-balancing behavior.

Result

The process enables deterministic, user-directed load-balancing for NVGRE traffic on Cisco Q100 and Q200 ASIC platforms.

Configure NVGRE hash field selection

  • NVGRE hash field selection is relevant primarily to transit devices that do not decapsulate NVGRE traffic.

  • Only applicable to Cisco Silicon One Q100 and Q200 ASIC-based systems.

Procedure

1.

Enter global configuration mode.

Example:

Router# configure

Access the global configuration prompt to apply platform-wide settings. Ensure you have the necessary privilege level for configuration changes.
2.

Set NVGRE load-balancing to use only the outer header, and exclude inner payload fields.

Example:

Router(config)# cef platform load-balancing nvgre payload exclude

This command configures the ASIC to ignore inner payload fields for NVGRE traffic when calculating the load-balancing hash, ensuring predictable balancing especially with non-IP NVGRE payloads.

The router now hashes only outer IP headers for NVGRE traffic when making load-balancing decisions.
3.

Save the configuration.

Example:

Router(config)# commit
Router(config)# end