VPN GR is an application of GR technology on a VPN. VPN GR ensures uninterrupted VPN traffic forwarding when an active/standby switchover is performed on a device transmitting VPN services. The purposes of VPN GR are as follows:
Reduce the impact of route flapping on the entire network during the switchover.
Reduce the impact on important VPN services.
Reduce single-point failures on PE or CE devices to improve VPN network reliability.
The device where an active/standby switchover occurs and its connected devices must have GR capabilities. They must retain forwarding information of all VPN routes within a time period to ensure uninterrupted VPN traffic forwarding. That is, the devices must support IGP GR, BGP GR, and LDP GR. If TE tunnels are deployed on the backbone network, the devices must support RSVP GR.
On a common BGP/MPLS VPN network, active/standby switchovers may occur on any PE, CE, or P device. The following explains active/standby switchovers on PE, CE, and P devices:
Active/standby switchover on a PE device
The GR process on a PE device is the same as that on the GR restarter in IGP GR, BGP GR, or LDP GR.
When a CE device connected to the PE device detects the restart of the PE device, the CE device acts the same as the GR helper IGP GR or BGP GR and retains all IPv4 routes in a period.
When the P device connected to the PE device detects the restart of the PE device, the P device acts the same as the GR helper in IGP GR, BGP GR, or LDP GR and retains all public IPv4 routes in a period.
When other PE devices (including those functioning as ASBRs) and the RR reflecting VPNv4 routes detect the restart of the PE device, they act the same as the GR helper in BGP GR, and retain all the public IPv4 routes and VPNv4 routes in a period.
Active/standby switchover on a P device
The GR process on a P device is the same as that on the GR restarter in IGP GR, BGP GR, or LDP GR.
When a P or PE device connected to this P device detects the restart, the P or PE device acts the same as the GR helper in IGP GR, BGP GR or LDP GR and retains all the public IPv4 routes in a period.
Active/standby switchover on a CE device
The GR process on a CE device is the same as that on the GR restarter in IGP GR or BGP GR.
When the PE device connected to the CE device detects the restart of the CE device, the PE device acts the same as the GR helper in IGP GR or BGP GR and retains all the private IPv4 routes in a period.
For details about IGP GR and BGP GR, see related description in S2720, S5700, and S6700 V200R019C10 Configuration Guide - IP Unicast Routing Configuration Guide.
For details about LDP GR and RSVP GR, see related description in the S2720, S5700, and S6700 V200R019C10 Configuration Guide - MPLS Configuration Guide.