isis timer holding-multiplier
Function
The isis timer holding-multiplier command sets the IS-IS holdtime to be a multiple of the interval at which Hello packets are sent.
The undo isis timer holding-multiplier command restores the default setting.
By default, the holdtime is three times the interval at which Hello packets are sent.
Format
isis timer holding-multiplier number [ level-1 | level-2 ]
undo isis timer holding-multiplier [ number ] [ level-1 | level-2 ]
Parameters
| Parameter | Description | Value |
|---|---|---|
| number | Specifies that the holdtime of a neighbor is a multiple of the interval at which Hello packets are sent. |
The value ranges from 3 to 1000 integer. By default, it is 3. |
| level-1 | Specifies the holdtime of a Level-1 neighbor. |
- |
| level-2 | Specifies the holdtime of a Level-2 neighbor. NOTE:
If neither Level-1 nor Level-2 is specified, the default level is Level-1 and Level-2. Parameters level-1 and level-2 are configured only on a broadcast interface that is enabled with IS-IS. |
- |
Views
Ethernet interface view, Ethernet sub-interface view, Eth-Trunk interface view, Eth-Trunk sub-interface view, Tunnel interface view, Loopback interface view, Dialer interface view, VLANIF interface view, Virtual-Template interface view
Usage Guidelines
Usage Scenario
Devices at both ends of a link establish a neighbor relationship by sending Hello packets to each other. After the neighbor relationship is established, both devices need to send Hello packets at a specified interval to maintain the neighbor relationship. If a device does not receive any Hello packet from its neighbor within a specified period of time, the device considers the neighbor to be Down. The specified time period is known as the neighbor holdtime.
For example, run the isis timer hello 20 command on a local device to set the interval at which Hello packets are sent to 20s. Then, run the isis timer holding-multiplier 4 command. The holdtime is 80s (four times the interval at which Hello packets are sent). If the interval at which Hello packets are sent is changed using the isis timer hello 20 command, the holdtime will be changed accordingly.
On broadcast networks, the DIS neighbor holdtime equals the interval at which Hello packets are sent multiplied by number, and non-DIS neighbor holdtime is one third of the DIS neighbor holdtime.
Configuration Impact
If the number value is set too large, the local device needs to wait a long time before detecting that the remote device has gone Down. This slows down IS-IS route convergence. If the value of number is set too small, the neighbor relationship will alternate between Up and Down when some Hello packets are lost due to transmission delays and errors on the network. This causes route flapping on the IS-IS network. Therefore, exercise caution when setting the value of number. Set the same interval at which Hello packets are sent and the same neighbor holdtime for all devices on the IS-IS network is recommended. This is to ensure that all devices detect link failures at the same time and guarantee timely IS-IS route convergence.
If a broadcast interface is emulated as a P2P interface through the isis circuit-type command or then restored to the broadcast interface through the undo isis circuit-type command, the number of Hello packets that IS-IS does not receive from a neighbor before the neighbor is declared Down is restored to the default value.
Example
# On GigabitEthernet0/0/0, set the number of Level-2 Hello packets sent by the neighbor but not received by IS-IS before the neighbor is declared to be Down to 6.
<sysname> system-view
[sysname] interface GigabitEthernet 0/0/0
[sysname-GigabitEthernet0/0/0] isis timer holding-multiplier 6 level-2