The set overload command sets the overload flag bit for non-pseudonode LSPs.
The undo set-overload command restores the set overload flag to zero.
By default, no overload bit is set.
set-overload [ on-startup [ timeout1 | start-from-nbr system-id [ timeout1 [ timeout2 ] ] | wait-for-bgp [ timeout1 ] ] [ send-sa-bit [ timeout3 ] ] ] [ allow { interlevel | external } * ]
undo set-overload
| Parameter | Description | Value |
|---|---|---|
| on-startup | Indicates the overload bit on system startup. When the router is restarted or a fault occurs, the overload bit remains set during the specified time. | - |
| timeout1 | Specifies the period for maintaining the overload bit after the system restarts. | The value ranges from 5 to 86400, in seconds. The default value of timeout1 is 600 seconds. |
| start-from-nbr system-id | Sets the duration of the overload bit of the system according to the state of the neighbors which the system ID specified. | - |
| timeout1 [ timeout2 ] | Sets the duration of the overload bit related to the
neighbor state.
|
The value of the timeout2 ranges from 5 to 86400, in seconds. The default value of the timeout2 is 1200 seconds (20 minutes). |
| wait-for-bgp | Sets the period for keeping the overload bit according to the status of the BGP convergence. | - |
| send-sa-bit | Specifies the overload bit remains in Hello packets after the device is started. | - |
| timeout3 | Specifies the period during which the overload bit remains in Hello packets after the device is started. | The value is an integer ranging from 5 to 120, in seconds. The default value is 30 seconds. |
| allow | Allows prefixes to be advertised. By default, the prefix is not advertised when the system enters the overload state. | - |
| interlevel | Allows IP prefixes learned from different IS-IS levels to be advertised when allow is configured. | - |
| external | Allows IP prefixes learned from other protocols to be advertised when allow is configured. | - |
Though LSPs configured with the overload flag are flooded in the network, the LSPs are not used when the routes that pass through the router configured with the overload flag are calculated. That is, after a router is configured with the overload flag, other routers ignore the router when performing SPF calculation. The direct routes on the router, however, cannot be ignored.
If you do not want other routers use the local router for SPF calculation, you can run the set-overload command on the local router and do not specify on-startup in the command. In this way, the system immediately sets the overload flag in the LSPs to be sent. To delete the overload flag, you can run only the undo set-overload command.
When the local router restarts or a fault occurs on the router, you can run the set-overload command and specify on-startup in the command if you do not want other routers to use the local router for SPF calculation.
When the memory of a router is not enough, the system automatically sets the overload flag in the LSPs to be sent, which is not related to whether users run the set-overload command.
By setting the overload flag, the problem that the network traffic is lost because the convergence speeds of BGP and IGP are not consistent is solved.
# Set the overload bit for IS-IS process 1.
<sysname> system-view
[sysname] isis
[sysname-isis-1] set-overload
Warning: The IS-IS process overload state will be set. Continue?[Y/N]
# Configure IS-IS process 1 to enter the overload state during the startup, and configure neighbor 0000.0000.0002 to maintain the overload state for 300 seconds after the neighbor goes Up within 1000 seconds during which the system starts.
<sysname> system-view
[sysname] isis
[sysname-isis-1] set-overload on-startup start-from-nbr 0000.0000.0002 300 1000
# Configure IS-IS process 1 to enter the overload state during the startup, advertise the IP prefix that is learned from IS-IS of different levels and prohibit IS-IS from advertising the IP prefix that is learned from other protocols.
<sysname> system-view
[sysname] isis
[sysname-isis-1] set-overload on-startup allow interlevel