Will lowering the carrier-delay on an interface configuration interfere with using BFD on the same interface?
If I configure carrier-delay msec 0 on an Ethernet interface the RIB is automatically notified of the physical link down event. In a scenario where the physical link doesn't go down but communications are not traversing the link (3rd party DWDM lamda for example) BFD would detect this.
Are there dangers to using a low carrier delay value with BFD, or is it recommended? Or will one simply superseed the other from a configuration perspective?
I would be using them in conjunction with interaface dampening and ip routing protocol purge interface in global configuration.
Best Answer
It won't interfere per se, but question is - what you're trying to achieve?
First of all, it's hardware dependent - you may be silently ignored using this command on software platforms. Essentially, you should drill down to supported/unsupported notes for your gear to check if it's available and working. Some platforms can tune up/down delays separately.
If you're trying to achieve fast convergence, use one protocol - by approaching the problem with the KISS principle. BFD seems to be best fit in case multiple protocols are used and they need information about the neighbor loss ASAP.
BTW,
carrier-delaywill only work on interfaces, that will signal up/down situation properly. Connections to shared media (like Ethernet switch) or to media that doesn't properly propagate up/down signal (some SDH/SONET/ATM gear) will cause problems anyway, so you should fall back to something that YOU control.