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Re: tracking down subnet announcement disappearing / dropping toa single provider
- From: Deepak Jain
- Date: Tue Dec 09 00:30:38 2003
More specific information would help, but this is what I'd think.
1) Flap dampening can exist in pretty discrete blocks of time.
2) Do you announce the entire /19 as a back up in case a provider does
not accept your /22 (many won't)
3) Set up a ping monitor to the service at the ASP, and a ping monitor
to a few of the upstream routers between you and the ISP. Make sure they
are running out of the /22. That way, if only the ASP disappears, you
can tell its not your problem. If everyone disappears, its probably
closer to home.
4) There are guys out there that monitor the flappiness of a route. If
you check route-views.oregon-ix.net for yours and the destination
address blocks, you will be able to see if the "global" internet saw any
5) If you are not advertising the /19 and you haven't nailed down the
/22 to a loopback or similar interface, you could be having a physical
interface that the /22 (say a connected route) is running go up/down and
your own router or ISP could be withdrawing it. Its always safer to
announce the larger aggregate and nail down your BGP routes.
Eric Kagan wrote:
I apologize if this is off-topic - I rarely post, mostly just monitor.
I am not posting this to [nsp] or [isp-bgp] for I don't believe the
following is a configuration problem on my side, but an operational one
of a certain provider. I am not going to sling dirt or put actual names
/ ASN, etc for now. I want to list the problem and if it is relevent I
can post more specific data or be contacted offlist with suggestions or
from the provider.
The problem is completely intermittent. 99% of the time everything
works fine. I have begged the customer to get their ASP's ISP involved
since I believe that is where the problem lies. They claim it is my
problem since we connect to them.....(Don't want to start a war here...I
I am Provider A and my customer cannot connect to an ASP through
Provider X. The problem lasts for what seems to be exactly 10, 15 or 30
minute intervals. I am announcing my /19 broken up into multiple /22
and /21's. It is only 1 of the /22 that has the problem. One of my
links is not going down and I do back backup routes through multiple
providers. It took me almost a month to confirm the problem because they
would call be *after* it happened and everything would look fine. I put
some monitors on the destination site and it will never test bad since
the monitors were on other subnets. They finally called me while it was
occuring and I did confirm I could not reach the site from any of the
IP's in that certain /22 subnet.
So, my point and questions:
Has anyone ever heard of such a problem ? I tried to search some
archives and google - but I can't really figure out what to search on
that won't result in 1000 + matches.
Is there any function or problem that might exist for exactly 10, 15 or
30 minutes (i.e. BGP Flap, subnet block filter / ACL ?) over and over ?
Should I contact provider X dircectly ? Will they work directly with me
? I believe my customers ASP opened a ticket with their ISP but with
all the layers and short time frame of the issue I don't think it will
get resolved quickly or easily.
Responses online or offline welcome. If anyone wants more specific info
posted to the forum (IP subnet blocks, Provider X, ASN, etc) please let
Commrail, Inc. dba
[email protected] <mailto:[email protected]>