The 3640 has a ATM 1A-OC3MM. The 1500 MTU is hard coded in the config. These sites were all set up before I started here 2 years ago. We're gradually replacing the ATM at the older sites with CSME.
thanks! Steve Pfister Technical Coordinator, The Office of Information Technology Dayton Public Schools 115 S. Ludlow St. Dayton, OH 45402 Office (937) 542-3149 Cell (937) 673-6779 Direct Connect: 137*131747*8 Email [email protected] >>> "Antonio Soares" <[email protected]> 9/18/2009 7:08 PM >>> This document might help you: Understanding Maximum Transmission Unit (MTU) on ATM Interfaces http://www.cisco.com/en/US/tech/tk39/tk371/technologies_tech_note09186a00800c8279.shtml This is what it says about Length Violations: "A router increments the AAL5 length violation counter when the calculated size of a reassembled packet fails to match the received value of the AAL5 length field regardless of the MTU. To understand how these violations can occur, you need to understand how a receiving ATM interface recognizes the last cell of a frame." What ATM NM do you have in the 3640 ? Did you change the default MTU from 4470 to 1500 ? Regards, Antonio Soares, CCIE #18473 (R&S) [email protected] -----Original Message----- From: Steven Pfister [mailto:[email protected]] Sent: sexta-feira, 18 de Setembro de 2009 19:09 To: Antonio Soares; [email protected] Subject: RE: [c-nsp] Need help troubleshooting CRC errors Thanks for the link... I have a little more detail about the problem now: 'show atm pvc x/y' shows: CrcErrors: 69402, SarTimeOuts: 2, OverSizedSDUs: 0, LengthViolation: 69294, CPIErrors: 0 Also, the router side shows, on 'show int': MTU 1500 bytes, sub MTU 1500, BW 155000 Kbit, DLY 80 usec, router side, on 'show atm int atm': Max. Datagram Size: 1558 8510 switch side, on 'show int': MTU 4470 bytes, sub MTU 4470, BW 155520 Kbit, DLY 0 usec, Would this be a problem? Steve Pfister Technical Coordinator, The Office of Information Technology Dayton Public Schools 115 S. Ludlow St. Dayton, OH 45402 Office (937) 542-3149 Cell (937) 673-6779 Direct Connect: 137*131747*8 Email [email protected] >>> "Antonio Soares" <[email protected]> 9/17/2009 11:45 AM >>> Try this document: CRC Troubleshooting Guide for ATM Interfaces http://www.cisco.com/en/US/tech/tk39/tk48/technologies_tech_note09186a00800c93ef.shtml Regards, Antonio Soares, CCIE #18473 (R&S) [email protected] -----Original Message----- From: [email protected] [mailto:[email protected]] On Behalf Of Steven Pfister Sent: quinta-feira, 17 de Setembro de 2009 15:39 To: [email protected] Subject: [c-nsp] Need help troubleshooting CRC errors Some of our older remote sites are connected via ATM. Two or three T1s come into an Cisco 8510, and from there a 155mbps OC3 connection over fiber to a 3640 router. Lately, I've been noticing that pretty much every one of them is showing what I think is a rather high receive error count on the 3640 end of the OC3 connection, and it all seems to be CRC errors. Not much of any errors are showing up on the 8510 end of the OC3 connection. For example, one site yesterday late afternoon showed 63, 763 receive errors for the day. Several others were in the 20Ks. I'm not really certain what the cause might be, or where to start. Can anyone help? Thanks! Steve Pfister Technical Coordinator, The Office of Information Technology Dayton Public Schools 115 S. Ludlow St. Dayton, OH 45402 Office (937) 542-3149 Cell (937) 673-6779 Direct Connect: 137*131747*8 Email [email protected] _______________________________________________ cisco-nsp mailing list [email protected] https://puck.nether.net/mailman/listinfo/cisco-nsp archive at http://puck.nether.net/pipermail/cisco-nsp/ _______________________________________________ cisco-nsp mailing list [email protected] https://puck.nether.net/mailman/listinfo/cisco-nsp archive at http://puck.nether.net/pipermail/cisco-nsp/
