route flap dampening

Mailman List Mirror (Read Only)
1

Hello all,
I was wondering how many of you use route flap dampening in your network.
If you have it enabled, what is the main reason?

Thank you!
Jonathan

2

Jonathan Park wrote:

Hello all,
I was wondering how many of you use route flap dampening in your network.
If you have it enabled, what is the main reason?

We've been considering it after the last flap around the world; perhaps with extremely short penalty times.

Jack

3

Jonathan Park wrote:

Hello all,
I was wondering how many of you use route flap dampening in your network.
If you have it enabled, what is the main reason?

We've been considering it after the last flap around the world; perhaps with extremely short penalty times.

<http://www.ripe.net/ripe/meetings/ripe-43/presentations/ripe43-routing-flap.pdf

4

Patrick W. Gilmore wrote:

We've been considering it after the last flap around the world; perhaps with extremely short penalty times.

<http://www.ripe.net/ripe/meetings/ripe-43/presentations/ripe43-routing-flap.pdf&gt;

Yeah, read the presentation several times, thus the short penalty times, and probably high thresholds.

The idea for me is to limit the harm of excessive flapping while not being paranoid. I've had a customer lose a lot of connectivity for 30 minutes after 3 or 4 flaps. I figure 5 minute ignore after about 10 flaps in a 10 minute period.

Jack

5

We're using Cisco 6509 MSFC2s for core engines with three 85% route
feeds and Cisco-default route flap suppression. Yeah, the default flap
suppression parameters are aggressive but we want to be sure we don't
hog precious CPU cycles from a nasty route flap and provide more
consistent routes to our downstreams. We can't take a full route table
(232k) due to TCAM limitations, so we have default routes anyway.
There's only a subtle impact to our customers with maybe a less
preferable, stable path versus a better, flapping one. A better
bargain in our book, but maybe not for others... CPU runs around
10-12% all day.

If we had more router CPU and no default routes, we'd probably have
dampening enabled but at very high thresholds under similar network
policies.

-D

6

I see.

Yes, I also heard that many networks have RFD enabled although it is not recommended, and
I was wondering why that would be.

So far from the responses, it seems to me that the reasons are:

1. to protect the network resources
2. to confine the flapping announcements made by customers locally within your network (easier to debug)

Do you have any other reasons if you use RFD?

Thanks Kevin and everyone for the responses.

Jonathan