IS IS Reducing Failure Detection
Table of Contents
Introduction
The amount of time an ISIS router takes to detect a failure can be tuned with some best practices, which relate to BFD, dampening, hello parameters or point to point timers.
Reducing Failure Detection
- The sooner networks can detect failure, the sooner they can react and propagate alternate routing information.
- Below are some of the features that help with detection:
- BFD
- IP Event Dampening
- Hello Parameters
- Point to Point Network type.
BFD
- Bidirectoin Forwarding Detection is an independent protocol that sends hellos on the physical interface.
- It has the publisher subscriber model, where ISIS subscribes to BFD events.
- Depending on the hardware platform, BFD can detect a failure in 100s of msec.
IP Event Dampening
- Prevents flapping interfaces from destabilizing the network of constant convergence.
- Using exponential delay, interface state is suppressed until interface is stable.
Hello Parameters
- Option should be used when BFD is not supported on an interface.
- Lowering the hello timers, increasing the bandwidth and CPU requirements.
Point to Point Network Type
- Eliminates the need to have a DIS or DR.
- No need to elect a new DIS.
- No need to flood CSNP for database synchronization.