This topic describes ECMP and LAG hashing for NVGRE flows on the Cisco 8000 Series Router, which lets transit routers load-balance NVGRE traffic across ECMP and LAG paths using the GRE payload.
Network Virtualization using Generic Routing Encapsulation (NVGRE) endpoint is a network device that
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acts as an interface between physical and virtual networks
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encapsulates Ethernet data frames for GRE tunnels, and
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decapsulates GRE packets to recover original Ethernet frames.
The NVGRE endpoint performs the following operations:
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The endpoint encapsulates Ethernet data frames for transport through a GRE tunnel.
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The system bridges and routes the encapsulated GRE packet to the destination.
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The destination endpoint decapsulates the GRE packet to recover the original Ethernet frame.
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The RFC 7637 document describes the NVGRE protocol.
| Feature Name |
Release Information |
Feature Description |
|---|---|---|
| ECMP and LAG Hashing for NVGRE Flows |
Release 25.4.1 |
Introduced in this release on: Fixed Systems (8010 [ASIC: A100])(select variants only*) *This feature is supported on:
|
| ECMP and LAG Hashing for NVGRE Flows |
Release 25.1.1 |
Introduced in this release on: Fixed Systems (8700 [ASIC: K100], 8010 [ASIC: A100])(select variants only*) *This feature is supported on:
|
| ECMP and LAG Hashing for NVGRE Flows |
Release 24.4.1 |
Introduced in this release on: Fixed Systems (8200 [ASIC: P100], 8700 [ASIC: P100])(select variants only*); Modular Systems (8800 [LC ASIC: P100])(select variants only*) *This feature is now supported on:
|
| ECMP and LAG Hashing for NVGRE Flows |
Release 7.5.2 |
This feature allows transit routers to load balance the GRE traffic, based on GRE payload. A transit node distributes incoming GRE traffic across ECMP and LAG paths in a GRE tunnel topology. A hashing function uses GRE payload that consists of inner Ethernet frame with destination MAC and source MAC addresses, to derive the traffic entropy. ECMP and LAG hashing is enabled on Cisco 8000 series routers by default. |
NVGRE uses the following header information for encapsulation:
| Header | Parameters |
|---|---|
| Outer Ethernet Header | Destination MAC address, Source MAC address |
| Outer IP Header | IPv4 and IPv6 addresses as delivery protocol for GRE |
| GRE Header | GRE protocol type 0x6558 (transparent Ethernet bridging) |
| GRE Payload | Inner Ethernet frame with Destination MAC address and Source MAC address |
For load balancing the GRE traffic, the transit router uses GRE payload that consists of inner Ethernet frame with destination MAC and source MAC addresses. The transit router derives the traffic entropy information from the GRE payload.
The hashing function considers the following parameters of GRE packets, along with Router ID, for load balancing the GRE traffic:
| Header | Parameters |
| Outer IPv4 Header | Source IP address, Destination IP address, IP Protocol (GRE) |
| Outer IPv6 Header | Source IP address, Destination IP address, Flow Label, IP Next Header (GRE) |
| Inner Header | Destination MAC address, Source MAC address, Ether Type |