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 decapsulation (GREv4)

Updated: July 31, 2026

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This topic describes unidirectional GRE decapsulation (GREv4) on the Cisco 8000 Series Router, where the router strips the outer GRE header and forwards the inner IPv4, IPv6, or MPLS payload to the next-hop router.

In unidirectional GRE decapsulation, the outer GRE header is decapsulated and the inner IPv4/IPv6/MPLS payload is forwarded to the next hop router. The following figure shows GRE decapsulation. In the figure, PE1 strips off outer GRE header and inner payload is forwarded as regular IPv4/IPv6/MPLS forwarding.

Configuration example

There are two methods to configure GRE tunnel decapsulation:

  1. CLI-based tunnel decapsulation configuration

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

  2. PBR-based tunnel decapsulation configuration

    class-map type traffic match-all test_gre1
                 match protocol gre
                 match destination-address ipv4 10.0.1.2 255.255.255.255
                 match source-address ipv4 10.10.10.1 255.255.255.255
                 end-class-map
policy-map type pbr P1-test
                 class type traffic test_gre1  decapsulate gre
vrf-policy vrf default address-family ipv4 policy type pbr input P1-test