route low-priority enable

Usage Scenario

The control plane and forwarding plane of the routing system are separated and cooperate with each other to forward data. The control plane learns and exchanges routing protocols, calculates routes, generates routing entries, and delivers the entries to the forwarding plane for packet forwarding. The forwarding plane receives and sends packets, encapsulates and decapsulates packets, queries routing entries, and forwards packets.

If the control plane has host routes and ARP entries with the same destination IP address as the host routes, the forwarding plane forwards packets based on the routes because the route priority on the control plane is higher than the ARP/ND priority. On the forwarding plane, packets are forwarded based on routes or ARP/ND entries, depending on which ones have higher priority. For example, if the route priority on the forwarding plane is lower than the ARP/ND priority, packets are forwarded based on ARP/ND entries. In this case, if the outbound interface of an ARP/ND entry is different from that of a route, for example, the outbound interface is manually specified in a static ARP entry, different forwarding behaviors will be performed.

Therefore, you need to run the route low-priority enable command to adjust the route priority on the forwarding plane to control whether packets are forwarded based on routes or ARP/ND entries.

Precautions

• In actual deployment, if there is no special requirement, to ensure consistent forwarding behaviors on the forwarding plane and control plane, it is recommended that the route priority on the forwarding plane be higher than the ARP/ND priority.
• This command takes effect only for newly generated routes. For existing routes, you need to run the refresh fib and refresh ipv6 fib commands to manually refresh routes after running this command. During route refresh, path switching may cause temporary traffic interruptions.
• In an upgrade scenario, after a device running V200R019C00SPC200 or an earlier version is upgraded to V200R019C00SPC210 or a later version, the route priority on the forwarding plane remains unchanged. That is, the route priority on the forwarding plane is lower than the ARP/ND priority. This conflicts with the default setting on switches running V200R019C00SPC210 or a later version. This is because the route priority on the forwarding plane is higher than the ARP/ND priority on these switches by default. To resolve the conflict, the route low-priority enable command is automatically generated in the configuration file of a switch.