- NANOG - lists.nanog.org

Re: PPPOE, MTU, and boom.
by Scott Silzer 19 Jul '01

19 Jul '01

If you are using an 827 try the ip tcp adjust-mss command. Taken from CCO: Resolved Caveats for Release 12.2(2)XH This section describes possibly unexpected behavior that are resolved in Release 12.2(2)XH. CSCds69577 The PPPoE standard sets the maximum transmission unit (MTU) of an Ethernet packet to 1492 bytes. If a host PC uses the default MTU of 1500 bytes, the router between the server and the host would drop those packets. Even though an ICMP message is sent to the website notifying it of the problem, some websites are programmed to ignore ICMP messages and would continue to send 1500-byte packets that will get dropped. Starting with Release 12.2(2)XH, you can resolve this problem by changing the value of the maximum segment size (MSS) contained in the MTU to 1492 or less. Use the following IOS command: ip tcp adjust-mss mss where mss is 1492 or less. This command does not require NAT to be configured. http://www.cisco.com/univercd/cc/td/doc/product/software/ios122/122relnt/17… http://www.cisco.com/univercd/cc/td/doc/product/software/ios122/122relnt/80… At 3:35 -0400 7/18/01, Alex Rubenstein wrote: >On Wed, 18 Jul 2001, Alex Rubenstein wrote: > >> It allows you to tinker with the Windows settings of TCP. I adjusted MTU >> to 1400, wham-o, all the sites I listed started working; including, what I >> didn't list before, the downloading of transactions via Quicken. Seems to >> be a fixall. > >I can tell it's getting late, when I reply to myself. > >In the scenerio where you have a router be the PPPOE client (in my test >case, it's a Cisco 827 running 12.1(3)XG4), things are still somewhat >broken. The 827 is routing between an ethernet and a PPPOE session, and >even with the 827 having the MTUs at 1492 or 1400, windoze boxen are still >stuck up there at 1500 and those sites don't work. I then use Mr. TCP and >set the ethernet card of the windows box to a MTU of 1400, and voila, it >works. > >This really sucks for those folks who will have many machines bechind said >router; it will require a Mr. TCP on each and every one of them. > >Sheesh. > > > >-- Alex Rubenstein, AR97, K2AHR, alex(a)nac.net, latency, Al Reuben -- >-- Net Access Corporation, 800-NET-ME-36, http://www.nac.net -- -- Scott A Silzer

2 1

Re: Apparent widespread Worldcom ATM failure
by Sean Donelan 19 Jul '01

19 Jul '01

On Wed, 18 July 2001, George William Herbert wrote: > My home/consulting business ISP and my current work > ISP's connectivity have been bit by what appears on first > examination to be a Worldcom ATM failure starting about > 2 hours ago (12:45 PST or so). It appears to be affecting > stuff as widely spread as both west and east coast and > connecting circuits. Does Worldcom have any websites updating the status of their ATM network? The UUNET site has no mention of this, but worldcom's networks aren't very integrated, so it was possible the uunet portion of worldcom was unaffected.

2 1

Update: CSX train derailment
by Sean Donelan 19 Jul '01

19 Jul '01

At 9pm (EDT) the newswires and CNN reported the Baltimore Fire Department had blocked most major highways and access roads to central Baltimore. 10 people have been treated for injuries including two firefighters. The following providers have updates on their public network status web sites about the cable cut and CSX train derailment Alternet/UUNET/Worldcom Abovenet/MFN Mindspring PSI The following providers are NOT reporting any problems on their public network status web sites. Either they haven't updated their web site, or they haven't experienced any affects from the train derailment. AT&T Exodus Cable & Wireless I do not know (or don't have access) to any network status web site for the following providers, so I do not know their status Genuity Level 3 Sprintlink Qwest Because the train derailment involves potentially hazardous materials, no provider has an estimated time to repair. Telecom repair crews will be allowed into the tunnel after the fire department and HAZMAT teams complete their work.

1 0

Re: Apparent widespread Worldcom ATM failure
by George William Herbert 19 Jul '01

19 Jul '01

Furthering my previous: I have been told that this outage totals 5 OC-48s and over 100 T-3 circuits around the country. No ETR reported. -george william herbert gherbert(a)retro.com

5 4

OT: @home contact
by Matt Levine 19 Jul '01

19 Jul '01

-----BEGIN PGP SIGNED MESSAGE----- Hash: SHA1 Apologies for posting to the list, but does anyone have a (or is anyone?) a high-level engineering contact @home ?? If so, can you please reply off-list? Very important. Sorry for taking up bw w/ this. Matt - -- Matt Levine @Home: matt(a)deliver3.com @Work: matt(a)eldosales.com ICQ : 17080004 PGP : http://pgp.mit.edu:11371/pks/lookup?op=get&search=0x6C0D04CF -----BEGIN PGP SIGNATURE----- Version: PGPfreeware 7.0.3 for non-commercial use <http://www.pgp.com> iQA/AwUBO1YpLMp0j1NsDQTPEQJYDgCgyseTBa2cQh1BJUxbJJgwLtM3MU8AoPiV X2NbCcFFEn4e1CZFMEDufub1 =0y4X -----END PGP SIGNATURE-----

1 0

DoS tracking paper
by Paul Blasquez 18 Jul '01

18 Jul '01

Hello, About 3 weeks back a gentleman posted a link to a paper on tracking DoS attacks quickly, the details involved tagging the traffic with community 666. I have since had a Win98 (Please flame me for running Win98) crash, and lost my bookmark to that page. Could someone please: a) Re-post the link b) Tell me if and where there is a database of nanog posts so I may search them. Thank you in advance. -Paul _________________________________________________________ Do You Yahoo!? Get your free @yahoo.com address at http://mail.yahoo.com

2 2

Apparent widespread Worldcom ATM failure
by George William Herbert 18 Jul '01

18 Jul '01

My home/consulting business ISP and my current work ISP's connectivity have been bit by what appears on first examination to be a Worldcom ATM failure starting about 2 hours ago (12:45 PST or so). It appears to be affecting stuff as widely spread as both west and east coast and connecting circuits. As I am not a direct customer I have no standing to ask them directly what went bang, so take this diagnosis with a grain of salt. -george william herbert gherbert(a)retro.com

1 0

Re: PPPOE, MTU, and boom.
by Alex Rubenstein 18 Jul '01

18 Jul '01

On Wed, 18 Jul 2001, Chris Wedgwood wrote: > On Wed, Jul 18, 2001 at 07:57:23AM +0100, Stephen J. Wilcox wrote: > > Could it be Path MTU/fragmentation issues on account of the low > MTU you have in combination with some ICMP issues where network > admins have some screwy setup? > > That's exactly what it is... a large (1500 byte probably) TCP datagram > with the DF bit set will be heading towards his edge device which are > PPPoE connected. Great domain, btw (f00f.org, brings back memories of division)... Anyway, a great stride was just made in my lab^H^H^Hbasement. First off, it appears a 'ip mtu 1492' on the Virtual-Template of the IOS Router aggregating the PPPOE session is not strictly enforced, especially with windows. Another words, I saw in the PPP debug that the MRU wasn't being negotiated. So, I found this really nifty utility, aptly named 'Mr. TCP': http://www.dslreports.com/front/drtcp.html It allows you to tinker with the Windows settings of TCP. I adjusted MTU to 1400, wham-o, all the sites I listed started working; including, what I didn't list before, the downloading of transactions via Quicken. Seems to be a fixall. -- Alex Rubenstein, AR97, K2AHR, alex(a)nac.net, latency, Al Reuben -- -- Net Access Corporation, 800-NET-ME-36, http://www.nac.net --

7 8

Correction: 209.177-222 Reverse DNS
by Larry Rosenman 18 Jul '01

18 Jul '01

CORRECTED SUBJECT... I just got off the phone with ARIN after discovering some incorrectly delegated in-addr.arpa zones. We (Internet America) have 209.196.64.0/18 and all of a sudden reverses weren't working. ARIN mistyped a transfer yesterday and got the 2nd Octet wrong. Verado, Inc (NET-VERADO-DC26) VERADO-DC26 209.177.128.0 - 209.222.143.255 Verado, Inc (NET-VERADO-DC27) VERADO-DC27 209.177.160.0 - 209.222.191.255 Internet America, Inc. (NET-IA-CR-2) IA-CR-2 209.196.64.0 - 209.196.127.255 They have corrected the database, and the next zone load should fix it. I thought others in the NANOG community might want to know. Larry Rosenman Sr. Network Engineer Internet America, Inc. 350 N. St. Paul, Suite 3000 Dallas, TX 75201 214-861-2571

1 0

209.196.177-222 reverse DNS
by Larry Rosenman 18 Jul '01

18 Jul '01

I just got off the phone with ARIN after discovering some incorrectly delegated in-addr.arpa zones. We (Internet America) have 209.196.64.0/18 and all of a sudden reverses weren't working. ARIN mistyped a transfer yesterday and got the 2nd Octet wrong. Verado, Inc (NET-VERADO-DC26) VERADO-DC26 209.177.128.0 - 209.222.143.255 Verado, Inc (NET-VERADO-DC27) VERADO-DC27 209.177.160.0 - 209.222.191.255 Internet America, Inc. (NET-IA-CR-2) IA-CR-2 209.196.64.0 - 209.196.127.255 They have corrected the database, and the next zone load should fix it. I thought others in the NANOG community might want to know. Larry Rosenman Sr. Network Engineer Internet America, Inc. 350 N. St. Paul, Suite 3000 Dallas, TX 75201 214-861-2571

1 0