Be careful with the -f option for ping, different flavors of ping use the flag differently, in most of my systems (in the Linux world), -f would mean flood, or roughly 100 pings per second. Additionally, on this flavor, -s would set packetsize (add 8 to packetsize to get the FULL packetsize (8 bytes of ICMP headerness)). Although I have not done MTU testing, it would seem -M (again, on Linux) selects path MTU discovery method.
- - - Jon ________________________________________ From: [email protected] [EMAIL PROTECTED] On Behalf Of Kevin Wigle [EMAIL PROTECTED] Sent: Saturday, September 20, 2008 4:45 PM To: 'InterMapper Discussion' Subject: RE: [IM-Talk] Anyone have MTU problems? we have had issues with MTU problems but usually on the client computers across slow links. You mention that a normal ping doesn't help - and you would be correct. However, try this: ping 123.456.789.001 -f -l 1500 The -f checks for fragmentation requirement The -l of course is length of packet sent If the response is normal then the MTU is good. If it isn't good, ping will respond with something like: Fragmentation required but df flag set. So you try the ping again with a smaller packet, say 1400 - until the ping doesn't fragment anymore. Kevin Wigle, CD CCSP, CCDP, CCNP, MCSE 2003 Security+, ITProject+, ISSP MCTS Windows Vista Configuration -----Original Message----- From: [email protected] [mailto:[EMAIL PROTECTED] On Behalf Of Konowal, Ed Sent: September-19-08 11:40 AM To: InterMapper Discussion Subject: [IM-Talk] Anyone have MTU problems? We have a infrequent but recurring problem with our telco. Every few weeks they seem to screw something up and we have an MTU problem, which we have to convience them is their problem. My problem is, I don't have a tool to scan all my sites with 1500 byte packets. Does anyone else have this problem? Anyone have a solution? When it's just an MTU problem, you can't see it with normal pings or even SNMP. To me my network looks good... Until a site calls to tell me it's not working. Ed Konowal Network Operations Supervisor Lee County School District ____________________________________________________________________ List archives: http://www.mail-archive.com/intermapper-talk%40list.dartware.com/ To unsubscribe: send email to: [EMAIL PROTECTED] ____________________________________________________________________ List archives: http://www.mail-archive.com/intermapper-talk%40list.dartware.com/ To unsubscribe: send email to: [EMAIL PROTECTED] ____________________________________________________________________ List archives: http://www.mail-archive.com/intermapper-talk%40list.dartware.com/ To unsubscribe: send email to: [EMAIL PROTECTED]
