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

Unidirectional GRE encapsulation (GREv4)

Updated: July 31, 2026

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This topic describes unidirectional GRE encapsulation (GREv4) on the Cisco 8000 Series Router, where the tunnel encapsulates an IPv4 or IPv6 payload inside a GRE header for transport across an IP network.

A tunnel configured using encapsulation mode performs encapsulation of IPv4/IPv6 payload inside the GRE header. The following figure shows GRE encapsulation. Routers in the IP cloud have no knowledge of encapsulated IP source address or destination address.

Configuration example

This example shows how to configure GRE tunnel encapsulation:

interface tunnel-ip1
  ipv4 address 101.0.1.1/24
  ipv6 address 101:0:1::1/64
  tunnel mode gre ipv4 encap
  tunnel source [ loopback1 | <any-ipaddres> | any-interface]
  tunnel destination [ 20.0.1.1/32 | 20.0.1.0/24 | 20.0.1.0/28]

router static
  address-family ipv4 unicast
  201.0.1.0/24 tunnel-1

router static
  address-family ipv6 unicast
  201:0:1::0/64 tunnel-1

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