AT&T -> Qwest ... Localpref issue?

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1

Hi folks,

Anyone else noticed a localpref change on Qwest network in regards to AT&T
prefixes? I noticed my AT&T assigned prefixes dropping to 80, causing my
backup transit peering with Centurylink to take preference with Qwest
originators ... All was working fine with my prepends .. But not anymore...

Any insight would be great. I haven¹t reached out to AT&T or Qwest yet.
Curious if this is a bigger change than just me.

Thanks,

-graham

2

Qwest uses 80 for peers; 100 for customers. As I'm sure Qwest had AT&T as a
peer prior to today (and you tagged as a customer), it probably should have
been 80 since the beginning. What was the local pref to AT&T before? Maybe
they found a misconfiguration on a router.

If your only objective is to make your Qwest peering "backup", send
community 209:70 to Qwest and it'll drop your local pref on their network to
70. This will cause their 80 local pref peering with AT&T to be preferred.

I also suggest you read:
http://www.onesc.net/communities/as209/
and
http://www.onesc.net/communities/as7018/

However, depending on if your network topology and situational circumstances
permit it, it may not be a bad idea to take on-net customer routes for
performance reasons.

3

Thanks Paul.

Localpref with Qwest on my AT&T prefixes was 100 until last week ... So my
prepends to balance between the two was working just fine for the past 2
years or so.
My announcements to CenturyLink to Qwest are coming out as 100.

I am not a direct customer of Qwest, so sending the community of 209:70
won¹t work (already tried that). I am a direct customer of CenturyLink and
unfortunately the two networks haven¹t really come together as one just yet.
I sent a note to AT&T ­ maybe the can help do something, as I reviewed the
communities with them and I am already doing what I need to do.

The main problem here is that our CenturyLink connection is pure crap ...
Even originating routes from their network, I had them take our AT&T (the
other transit at this particular POP) - faster and less hops (go figure).
At our other pops with more than 1 transits, we like to utilize both as much
as possible.

Contract is up in December ... can¹t wait until it¹s gone.

4

I should also note that Centurylink has been less than cooperative on even
thinking about changing my routes to a pref of 70 on our behalf (they don't
accept communities). I think time to get the account rep involved ...

5

"they don't accept communities"??!? Just... wow. :wink:

(That's if they flat out don't support it - there's a separate ring of Hell
reserved for the ones who do support it but forget to document the part
about singing the Zimbabwe national anthem backwards while standing on
your head...)

6

This is one of the reasons that I thought a useful output from the opsec or idr working group would be a documented set of community functions. Not mapped to values mind you. but I really like to say to providers "do you support rfc blah communities" or "what's your rfc blah community mapping" rather than "what communities do you support".

7

Graham,

We have the same issue as you, although it has been that way since the
beginning. Our primary is Level 3, and backup CenturyLink.

We have been forced to only announce certain prefixes out each in
order to get a balance. CenturyLink has told me that they do not
support communities.

Unfortunately I have much longer on my contract than you.

We are even having problems routing to AOL & Yahoo on CenturyLink.
I've had to refuse those routes from CenturyLink since Yahoo prepends
out Level 3.

8

I don't like it as it's a slower to converge solution, but look into BGP
conditional advertising.

Or better yet, tell AM you want to move to the "Qwest" internet product.
You want to peer with AS 209.