Re: BGP Dampening question

[Bruce Pinsky]

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D Train wrote:
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Have you considered IP Event Dampening?
http://www.cisco.com/en/US/partner/products/sw/iosswrel/ps1829/products_feature_guide09186a00800ad25b.html

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| - You start. We finish.
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Re: BGP Dampening question

[Iljitsch van Beijnum]

On 16-jul-04, at 5:46, D Train wrote:
If I keep seeing the physical connection to City A flapping, of course 
bgp will flap, but will I be able to use route dampening to control 
the instability
No. BGP flap dampening only works on routes that go up and down 
periodically while the BGP session they're learned over stays up. When 
the session goes down the dampening info is removed.

But it doesn't matter: you're screwed both ways. If you keep routing 
stable you lose packets, if you import the flapping into your routing 
protocols those become unstable. You need stable links.

Re: BGP Dampening question

[D Train]

<<
 
It isn't so much that one of our links are flapping all of the time, but in our enterprise we have over 1000 locations, which can be 10 or 15 circuits flapping at one given time. This is more for management/administration reasons, other than just wheather or not the router can with stand the torture. Each location is its own AS, and we are running EBGP between all of our ASs, internally inside our global AS, if that makes sense. If it were just a couple of cirucits dying on us, that would be fine, but we are trying to come up with some sort of dynamic solution so if our primary circuit is flapping, we won't be flopping back in forth, from our primary to our secondary, from BGP routes, to default route, and vice-versa, keeping our network stable . 
 
<<
 
If you don't recommend BGP dampening to fix our problem, what else is there, that I have not found or thought of yet. Is there a true dynamic solution to our problem?
 
<<
 
So you could still use dampening successfully, even though the bgp session keeps resetting. Does your peering session have to remain stable, with you just dampening some routes, or can your session keep bouncing, and it will still know to store these routes in either their history state, or dampening state?
 
D-
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Re: BGP Dampening question

[Patrick W Gilmore]

On Jul 15, 2004, at 11:46 PM, D Train wrote:
I was needing to know if anyone could assist in helping me find a 
solution to a problem I am experiencing. Here is the scenario:

I have an AS 20, that has 2 circuits one to city A, and one to City B. 
City A and City B are in another AS, lets say AS 1. In my AS 20, I am 
learning the default route via EBGP, from City A,through my primary 
link, and also have a static route configured to traverse my secondary 
link, to City B. If I keep seeing the physical connection to City A 
flapping, of course bgp will flap, but will I be able to use route 
dampening to control the instability in AS 20? Will I be able to tweak 
route dampening to where I will be able to just use the secondary for 
say a set time, before it will try to use the primary link, even if 
this connection is continuously flapping? I am hoping that I will be 
able to tweak dampening to where it will just use my secondary link, 
until I can fix my primary link, w/o having to manually shut the 
interface, or shut bgp?
I apologize if this is a bit off topic...
First, this is about the most on-topic post I've seen in a while.
Second, yes, you can do what you want with flap dampening.  Your router 
will penalize the announcements from A for every time it flaps, and 
will wait until it has stopped flapping for a user definable time 
before sending packets to A again.

That said, I would not use flap dampening for this.  If A is flapping 
THAT much, time to get another provider, or another local loop.  If it 
only flaps occasionally, not a big deal, the routers will handle it.

Besides, since you only have connectivity to one AS, there is really no 
need for you to announce to the global table at all.  Just use a 
private AS to get the routes and have the other AS originate your CIDR 
from their AS.

You can still get the default route, still static to the backup link.  
If the circuit to A flaps, routing will converge quickly.  You can 
tweak the timers to do it very quickly, since no one else is listening.

In fact, you do not even need BGP.  This set up is simple enough to use 
anything else - even RIP.  (I'm serious - this is a trivial routing 
exercise, so one could even argue the most brain-dead protocol is best 
suited for it.)

--
TTFN,
patrick

BGP Dampening question

[D Train]

I was needing to know if anyone could assist in helping me find a solution to a problem I am experiencing. Here is the scenario:
 
I have an AS 20, that has 2 circuits one to city A, and one to City B. City A and City B are in another AS, lets say AS 1. In my AS 20, I am learning the default route via EBGP, from City A,through my primary link, and also have a static route configured to traverse my secondary link, to City B. If I keep seeing the physical connection to City A flapping, of course bgp will flap, but will I be able to use route dampening to control the instability in AS 20? Will I be able to tweak route dampening to where I will be able to just use the secondary for say a set time, before it will try to use the primary link, even if this connection is continuously flapping? I am hoping that I will be able to tweak dampening to where it will just use my secondary link, until I can fix my primary link, w/o having to manually shut the interface, or shut bgp? 
I apologize if this is a bit off topic...
 
TIA, D-
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