Configuring Attributes for Hello Packets
Context
IS-IS maintains neighbor relationships between neighbors by sending and receiving Hello packets. If the local device does not receive Hello packets from its neighbor within a specified period, the device considers the neighbor Down.
- If the interval for sending Hello packets is too short, more system resources are consumed to send Hello packets, causing a heavy CPU load.
- If the holdtime of neighboring devices is too long, the local
device needs to spend much time detecting the failure of neighbors,
slowing down IS-IS route convergence. If the holdtime of neighboring
devices is too short, some Hello packets may be lost or become incorrect
because of network transmission delay and errors. This will cause
neighbor relationships to frequently alternate between Up and Down
and lead to route flapping on the IS-IS network.
You are advised to set the same interval for sending Hello packets and same holding multiplier of neighboring devices on all the devices on the IS-IS network. This method prevents IS-IS route convergence from being slowed down when some devices detect link failures at a lower speed than other devices.