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Ciscos, BGP, L2TPV3 pseudowires and loopback IPs
by James Smallacombe 12 Nov '10

12 Nov '10

A simpler question(s) than it sounds: Customer just brought up their first BGP session at a new location. It is up fine with a full routing table, the second provider hookup is a few weeks away. The provider allocated a /24 (x.x.1.0/24) for the network and a /30 for the PTP connection (x.x.129.172/30). For the initial setup, I did not configure a loopback, I just put x.x.129.174 on the WAN interface and set up the neighbor as x.x.129.173. It's working fine. We will need to set up a L2TPV3 tunnel to their old location (single homed, no BGP on that side). Upon initial reading of Cisco docs to do this, we will need a routable IP on a loopback interface for starters. Using one from the /24 LAN is out unless we subnet it, which we don't want to do. So the question is, can I just "move" the PTP IP address x.x.129.174 from the WAN interface to the loopback like this? interface Loopback0 ip address x.x.129.174 255.255.255.252 (that's the mask we're using on the WAN- Cisco's loopback examples show .255) interface WAN1 (actually a gigether) ip unnumbered loopback0 (or no ip addr?) neighbor x.x.128.173 update-source Loopback0 Does this look even close to right? Or do we need another, single routabe IP from the provider for the loopback? Also, I am assuming we don't need separate loopback interfaces for BGP as for the Bridge/Tunnel. What about when the second provider comes up? A second or third loopback to nail up their WAN IP? ***OR*** is there a way to put their WAN I/F IP on the loopback and take it off their LAN Ether...and then do IP unnum loop0 on the LAN? TIA, James Smallacombe PlantageNet, Inc. CEO and Janitor up(a)3.am http://3.am =========================================================================

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Gratuitous syn/ack
by Pete Carah 12 Nov '10

12 Nov '10

I'm seeing a significant number (about 1/minute 24 hr/day) of syn/ack packets coming from port 80 of random addresses to random ports on my nameserver and a few other systems. This isn't enough traffic to be really annoying, but is curious. I wonder if the simple explanation (backscatter from syn floods with spoofed source addresses) is more likely, or if there are some probing techniques in "normal" use that use these packets (one could accomplish a traceroute using port 80 packets in either direction...) -- Pete

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Extra latency at ATT exchange for UVerse
by Srikanth Sundaresan 12 Nov '10

12 Nov '10

Can anyone explain why ATT's UVerse adds significant delay to packets compared to their ADSL service? For example, pinging 8.8.8.8 from an ADSL gateway shows a latency of ~10ms. From an UVerse gateway, it's about 40ms. Of the extra 30ms, about 10ms can be explained by the fact that UVerse last hop is interleaved. ADSL seems to have Fastpath enabled more often than not (at least in my city). The extra 20ms is more interesting. By pinging each hop obtained by tracerouting to 8.8.8.8, the extra latency seems to be added on the exchange between ATT and Google. It's not just for 8.8.8.8. The same holds for other hosts too. ATT seems to add 20ms when it hands off a (UVerse) packet at an exchange. Thanks, Srikanth

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fiber / patch equipment suppliers
by bas 11 Nov '10

11 Nov '10

Hi All, Here an email from a Euro starting a POP in the US. Who are your favorite suppliers of patch fibers and accessories in the Ashburn (VA) area? Off list replies please, rather not pollute nanog any more than needed. Thanks in advance, Bas

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Re: Ciscos, BGP, L2TPV3 pseudowires and loopback Ips
by David Freedman 11 Nov '10

11 Nov '10

>> interface WAN1 (actually a gigether) >> ip unnumbered loopback0 (or no ip addr?) >> >That's not correct. Actually, was fixating on the fact that he has ethernet WAN and last I checked IOS doesn't have unnumbered-to-ethernet capability (well not true, recently they introduced unnumbered SVI support, don't know if it actually works on anything else) Dave. -- David Freedman Group Network Engineering david.freedman(a)uk.clara.net Tel +44 (0) 20 7685 8000 Claranet Group 21 Southampton Row London - WC1B 5HA - UK http://www.claranet.com Company Registration: 3152737 - Place of registration: England All the information contained within this electronic message from Claranet Ltd is covered by the disclaimer at http://www.claranet.co.uk/disclaimer

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Routing filters PA /31-/34
by Jack Bates 11 Nov '10

11 Nov '10

Anyone have any data on current and trends for routing /31-/34 of PA space via BGP? What type of isolation metrics might I be looking at today as well as in 1-2 years? Jack

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Thanks guys!
by Green, Timothy 11 Nov '10

11 Nov '10

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How do I change my email?
by Green, Tim R 11 Nov '10

11 Nov '10

I'm leaving the job attached to this email. This is my new email address timothy.green(a)mantech.com Thanks, Tim

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Emulating a cellular interface
by Saqib Ilyas 11 Nov '10

11 Nov '10

Greetings NANOGers A friend of mine is doing some testing where he wishes to emulate a cellular-like interfaces with random drops and all, out of an ethernet interface. Since we have plenty of network and system ops on the list, I thought we might have luck posting the question here. Is anyone aware of a simple tool to do this, other than rather involved configuration of iptables? Thanks and best regards -- Muhammad Saqib Ilyas PhD Student, Computer Science and Engineering Lahore University of Management Sciences

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re: AS path question.
by Nick Olsen 11 Nov '10

11 Nov '10

They are prepending routes. Looks like both 43022 are prepending, As well as 47359...Multiple times... They do this to make that route look "bad" so it comes in other transit they have. Nick Olsen Network Operations (855) FLSPEED x106 ---------------------------------------- From: "Greg Whynott" <Greg.Whynott(a)oicr.on.ca> Sent: Wednesday, November 10, 2010 3:23 PM To: "nanog(a)nanog.org list" <nanog(a)nanog.org> Subject: AS path question. Recently I adjusted the maxas-limit option on our router, logs started reporting routes being refused because the AS path is to long. seems to work as expected. when I looked at the logs I was a bit confused at what i was looking at... why is it there are multiple AS's in the path that appear to be the same AS? I expected an AS path comprised of mostly unique ASs. instead of this: 476330: Nov 10 14:55:07.247 EDT: %BGP-6-ASPATH: Long AS path 549 26677 6939 21011 43022 43022 43022 43022 43022 47359 47359 47359 47359 47359 47359 47359 47359 received from isp router: More than configured MAXAS-LIMIT i expected it would look more like: 476330: Nov 10 14:55:07.247 EDT: %BGP-6-ASPATH: Long AS path 549 26677 6939 21011 43022 47359 received from . .. . thanks for your time again, greg -- This message and any attachments may contain confidential and/or privileged information for the sole use of the intended recipient. Any review or distribution by anyone other than the person for whom it was originally intended is strictly prohibited. If you have received this message in error, please contact the sender and delete all copies. Opinions, conclusions or other information contained in this message may not be that of the organization.

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