route-select delay
Function
The route-select delay command configures a delay for selecting routes.
The undo route-select delay command deletes the delay for selecting routes.
The default delay is 0, indicating that routes are selected without a delay.
Parameters
| Parameter | Description | Value |
|---|---|---|
| delay-value | Specifies the delay for selecting routes. | The value is an integer that ranges from 0 to 3600, in seconds. |
Views
BGP view, BGP-IPv4 unicast address family view, BGP-VPN instance IPv4 address family view, BGP-IPv6 unicast address family view, BGP-VPN instance IPv6 address family view, BGP-VPNv4 address family view, BGP-VPNv6 address family view, BGP-IPv4 multicast address family view, BGP L2VPN-AD address family view
Usage Guidelines
Usage Scenario
In a scenario in which primary and backup routes exist, packets may get lost after traffic switches back to the primary path from the backup path. Figure 1 illustrates a VPN FRR scenario. PE3 and CE2 connect both to PE1 and PE2. The primary path is PE3 -> PE1 -> CE2, and the backup path is PE3 -> PE2 -> CE2. CE2 uses BGP to communicate with PE1 and PE2. FRR is configured on PE3. If PE1 restarts or the link between PE3 and PE1 is disconnected, traffic switches from the primary path to the backup path. After the primary path recovers, traffic switches back to the primary path. If PE3 completes refreshing forwarding entries before PE1 does so, PE1 may temporarily fail to forward traffic after a switchback. As a result, packet loss may occur. The severity of packet loss is proportional to the number of routes stored on PE1.
To solve this problem, run the route-select delay command on PE3 to configure a delay for selecting a route to PE1. An appropriate delay ensures that traffic switches back to the primary path after PE1 completes refreshing forwarding entries.
Precautions
If you run the route-select delay command repeatedly, the latest configuration overrides the previous configurations. If a route selection delay timer has started when you configure a new route select delay, the new route selection delay takes effect since the next route selection.