[c-nsp] Level3/Cogent/HVDataNet specific routing problem -looking for suggestions

[John van Oppen]

If you are trying to influence the return-traffic from cogent to go to
you via another upstream and not level3, you can use the level3
community that will prepend a few times to cogent.   We do this with
great success as we have three providers and try to keep some tier 1s
coming in each of them based on how close the peerings between providers
are.

If you want specific help with level3 communities you can email me
off-list and I will send you some examples on what we do as we also have
AS3356 transit and keep all of the traffic from cogent -> us on another
upstream for performance reasons.


Thanks,

John

-----Original Message-----
From: cisco-nsp-bounces at puck.nether.net
[mailto:cisco-nsp-bounces at puck.nether.net] On Behalf Of Jonathan
Crawford
Sent: Friday, November 16, 2007 10:08 AM
To: 'Tim Durack'; 'Cisco-nsp'
Subject: Re: [c-nsp] Level3/Cogent/HVDataNet specific routing problem
-looking for suggestions

The prepeding should have nothing to do with your lack of connectivity
through Cogent. All the prepending would do is possibly make another
route
look more desireable due to the as-path. They already append their ASN
when
you pass through their AS.

As a second note... are you allowing UDP ports for traceroute?

I can trace 208.74.141.252 with ICMP, but with UDP I drop right at your
edge. Cisco uses UDP by default.

-----Original Message-----
From: cisco-nsp-bounces at puck.nether.net
[mailto:cisco-nsp-bounces at puck.nether.net] On Behalf Of Tim Durack
Sent: Friday, November 16, 2007 8:47 AM
To: Cisco-nsp
Subject: [c-nsp] Level3/Cogent/HVDataNet specific routing problem -
looking
for suggestions

Having difficulties with routing through a Level3 circuit:

Traceroute using 67.99.58.158 source address:

RTR-3#traceroute 38.102.194.142

Type escape sequence to abort.
Tracing the route to HudsonValleyDataNet.demarc.cogentco.com
(38.102.194.142)

  1 67.99.58.157 [AS 6395] 8 msec 4 msec 4 msec
  2 so-7-0-0.edge5.NewYork1.Level3.net (4.68.63.17) [AS 6395] 12 msec
4 msec 4 msec
  3 ae-32-89.car2.NewYork1.Level3.net (4.68.16.132) [AS 6395] 4 msec 4
msec 4 msec
  4 COGENT-COMM.car2.NewYork1.Level3.net (4.68.111.46) [AS 6395] 8
msec 4 msec 4 msec
  5 v3503.na21.b001105-25.jfk05.atlas.cogentco.com (38.20.32.162) [AS
6395] 12 msec 12 msec 8 msec
  6 HudsonValleyDataNet.demarc.cogentco.com (38.102.194.142) [AS 6395]
152 msec *  8 msec


Traceroute using 208.74.141.252 source address:

RTR-3#traceroute
Protocol [ip]:
Target IP address: 38.102.194.142
Source address: 208.74.141.252
Numeric display [n]:
Timeout in seconds [3]:
Probe count [3]:
Minimum Time to Live [1]:
Maximum Time to Live [30]:
Port Number [33434]:
Loose, Strict, Record, Timestamp, Verbose[none]:
Type escape sequence to abort.
Tracing the route to HudsonValleyDataNet.demarc.cogentco.com
(38.102.194.142)

  1 67.99.58.157 [AS 6395] 4 msec 4 msec 4 msec
  2 so-7-0-0.edge5.NewYork1.Level3.net (4.68.63.17) [AS 6395] 4 msec 4
msec 4 msec
  3 ae-32-89.car2.NewYork1.Level3.net (4.68.16.132) [AS 6395] 4 msec
    ae-22-79.car2.NewYork1.Level3.net (4.68.16.68) [AS 6395] 4 msec 4
msec
  4 COGENT-COMM.car2.NewYork1.Level3.net (4.68.111.46) [AS 6395] 20 msec
4
msec
  5  *  *  *
  6  *  *  *
  7

I'm assuming 208.74.141.0/24 is getting dropped at hop 5 due to
filtering. Not having issues anywhere else.

I have a ticket open with Level3, but would like to see if I can work
around this with some community triggered prepending.

Looking at Level3's community support, I think I could get
208.74.141.0/24 prepended for Cogent peering:

--------------------------------------------------------
customer traffic engineering communities - Prepending
--------------------------------------------------------
65001:0   - prepend once  to all peers
65001:XXX - prepend once  at peerings to AS XXX
65002:0   - prepend twice to all peers
65002:XXX - prepend twice at peerings to AS XXX
65003:0   - prepend 3x to all peers
65003:XXX - prepend 3x    at peerings to AS XXX
65004:0   - prepend 4x to all peers
65004:XXX - prepend 4x    at peerings to AS XXX


So something like:

route-map level3-out
 set community 65001:174
!

Does that have a chance of working? Do I have to soft-reset the
session to get the community propagated?

Thanks,

Tim:>
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