Re: Ping ethernet interface with datagram over 150 [7:63085]
How are you doing, Marco? I actually DID think about this for a bit. To my knowledge Ethernet MTU is 1500, and ATM MTU depend on the connection. In my case we have 3M connection, but I am not sure what the MTU is because I have not looked at my partner company's 'sh int' result. But I would assume that it would be bigger than 1500. But at any rate, I am not sure if this will result in the ping failure. My understanding of MTU is that, if a node gets a datagram which is bigger than the set MTU, it will just break it up to smaller fragments and process them. If I am missing something, please let me know. Thank. Sean KimM.C. van den Bovenkamp wrote: > > Sean Kim wrote: > > > There isn't any problem with connection of performance. But > I am very > > curious about why this is happening. > > Does anybody have any idea why this would happen? Or can > anybody give me a > > clue as to how to approach this problem? > > Think MTU difference. > > Regards, > > Marco. > > Message Posted at: http://www.groupstudy.com/form/read.php?f=7&i=63090&t=63085 -- FAQ, list archives, and subscription info: http://www.groupstudy.com/list/cisco.html Report misconduct and Nondisclosure violations to [EMAIL PROTECTED]
Re: Ping ethernet interface with datagram over 150 [7:63085]
Hello Erick, If that's the case, than wouldn't I have problem pinging any nodes (with over 1500 byte datagram) across the ATM link? But I do not have pinging any other nodes. It only happens, when I am sitting on my router pinging the other router's interface and vice-versa... Sean Erick B. wrote: > > The ATM connection (provider) is probably limiting > payload size to 1500. They may doing some form of > traffic policing - common these days. Ethernet LAN MTU > is 1500 so there really isn't a need to send greater > than that across ATM in this case. > > --- Sean Kim wrote: > > Hello, > > > > My company has this 3rd party connection through > > ATM. The ATM TA has an > > ethernet outlet which is and connected to our core > > router. Our parner > > company is connected with anATM module on their > > router. > > > > Recently, I was told by our partner company that > > they were running ping test > > and they could not ping my ethernet interface (on > > the core router) with > > datagram over 1500 byte. > > > > From both the router itself and my workstation, I > > pinged my own interface > > with 1600 byte, and I was able to ping it. But when > > I pinged my partner > > company's interface with 1600 byte, it failed. > > > > In general it seems that pinging from other nodes, > > there is no problem, but > > sitting on the routers itself, pinging the other > > routers interface with the > > datagram size of over 1500 is failing. > > > > There isn't any problem with connection of > > performance. But I am very > > curious about why this is happening. > > Does anybody have any idea why this would happen? > > Or can anybody give me a > > clue as to how to approach this problem? > > > > Thank you in advance. > > > > Sean Kim > [EMAIL PROTECTED] > > > __ > Do you Yahoo!? > Yahoo! Shopping - Send Flowers for Valentine's Day > http://shopping.yahoo.com > > Message Posted at: http://www.groupstudy.com/form/read.php?f=7&i=63092&t=63085 -- FAQ, list archives, and subscription info: http://www.groupstudy.com/list/cisco.html Report misconduct and Nondisclosure violations to [EMAIL PROTECTED]
Re: Ping ethernet interface with datagram over 150 [7:63085]
Try this ping from the nodes: ping -f -l 1600 node-on-other-side-of-ATM If this doesn't ping, then the ATM connection is only letting 1500 through. The Ethernet router interface is fragmenting packets to 1500 bytes (1600 packet becomes 2 packets) from the nodes. When doing a ping from the router, if using ATM interface as source then it is going across ATM as 1600 bytes. --- Sean Kim wrote: > Hello Erick, > > If that's the case, than wouldn't I have problem > pinging any nodes (with > over 1500 byte datagram) across the ATM link? > But I do not have pinging any other nodes. It only > happens, when I am > sitting on my router pinging the other router's > interface and vice-versa... > > Sean > > > > Erick B. wrote: > > > > The ATM connection (provider) is probably limiting > > payload size to 1500. They may doing some form of > > traffic policing - common these days. Ethernet LAN > MTU > > is 1500 so there really isn't a need to send > greater > > than that across ATM in this case. > > > > --- Sean Kim wrote: > > > Hello, > > > > > > My company has this 3rd party connection through > > > ATM. The ATM TA has an > > > ethernet outlet which is and connected to our > core > > > router. Our parner > > > company is connected with anATM module on their > > > router. > > > > > > Recently, I was told by our partner company that > > > they were running ping test > > > and they could not ping my ethernet interface > (on > > > the core router) with > > > datagram over 1500 byte. > > > > > > From both the router itself and my workstation, > I > > > pinged my own interface > > > with 1600 byte, and I was able to ping it. But > when > > > I pinged my partner > > > company's interface with 1600 byte, it failed. > > > > > > In general it seems that pinging from other > nodes, > > > there is no problem, but > > > sitting on the routers itself, pinging the other > > > routers interface with the > > > datagram size of over 1500 is failing. > > > > > > There isn't any problem with connection of > > > performance. But I am very > > > curious about why this is happening. > > > Does anybody have any idea why this would > happen? > > > Or can anybody give me a > > > clue as to how to approach this problem? > > > > > > Thank you in advance. > > > > > > Sean Kim > > [EMAIL PROTECTED] > > > > > > __ > > Do you Yahoo!? > > Yahoo! Shopping - Send Flowers for Valentine's Day > > http://shopping.yahoo.com [EMAIL PROTECTED] __ Do you Yahoo!? Yahoo! Shopping - Send Flowers for Valentine's Day http://shopping.yahoo.com Message Posted at: http://www.groupstudy.com/form/read.php?f=7&i=63101&t=63085 -- FAQ, list archives, and subscription info: http://www.groupstudy.com/list/cisco.html Report misconduct and Nondisclosure violations to [EMAIL PROTECTED]
Re: Ping ethernet interface with datagram over 150 [7:63085]
Hello Erick, My understanding is that, with the ethernet MTU being 1500, pinging with the datagram size of bigger than 1500 byte (with the non-fragment bit set) won't leave my NIC card. I tried the command anyway, and I got an error message saying that the packet needs to be fragmented first but DF is set. When tryed the same from the router, it failed. But I am guessing it's probably because of the same reason. The packet has to go out the ethernet interface and 1500+ with NF set will not go out the interface because it exceeds the MTU. Sean Erick B. wrote: > > Try this ping from the nodes: > > ping -f -l 1600 node-on-other-side-of-ATM > > If this doesn't ping, then the ATM connection is only > letting 1500 through. The Ethernet router interface is > fragmenting packets to 1500 bytes (1600 packet becomes > 2 packets) from the nodes. When doing a ping from the > router, if using ATM interface as source then it is > going across ATM as 1600 bytes. > > --- Sean Kim wrote: > > Hello Erick, > > > > If that's the case, than wouldn't I have problem > > pinging any nodes (with > > over 1500 byte datagram) across the ATM link? > > But I do not have pinging any other nodes. It only > > happens, when I am > > sitting on my router pinging the other router's > > interface and vice-versa... > > > > Sean > > > > > > > > Erick B. wrote: > > > > > > The ATM connection (provider) is probably limiting > > > payload size to 1500. They may doing some form of > > > traffic policing - common these days. Ethernet LAN > > MTU > > > is 1500 so there really isn't a need to send > > greater > > > than that across ATM in this case. > > > > > > --- Sean Kim wrote: > > > > Hello, > > > > > > > > My company has this 3rd party connection through > > > > ATM. The ATM TA has an > > > > ethernet outlet which is and connected to our > > core > > > > router. Our parner > > > > company is connected with anATM module on their > > > > router. > > > > > > > > Recently, I was told by our partner company that > > > > they were running ping test > > > > and they could not ping my ethernet interface > > (on > > > > the core router) with > > > > datagram over 1500 byte. > > > > > > > > From both the router itself and my workstation, > > I > > > > pinged my own interface > > > > with 1600 byte, and I was able to ping it. But > > when > > > > I pinged my partner > > > > company's interface with 1600 byte, it failed. > > > > > > > > In general it seems that pinging from other > > nodes, > > > > there is no problem, but > > > > sitting on the routers itself, pinging the other > > > > routers interface with the > > > > datagram size of over 1500 is failing. > > > > > > > > There isn't any problem with connection of > > > > performance. But I am very > > > > curious about why this is happening. > > > > Does anybody have any idea why this would > > happen? > > > > Or can anybody give me a > > > > clue as to how to approach this problem? > > > > > > > > Thank you in advance. > > > > > > > > Sean Kim > > > [EMAIL PROTECTED] > > > > > > > > > __ > > > Do you Yahoo!? > > > Yahoo! Shopping - Send Flowers for Valentine's Day > > > http://shopping.yahoo.com > [EMAIL PROTECTED] > > > __ > Do you Yahoo!? > Yahoo! Shopping - Send Flowers for Valentine's Day > http://shopping.yahoo.com > > Message Posted at: http://www.groupstudy.com/form/read.php?f=7&i=63143&t=63085 -- FAQ, list archives, and subscription info: http://www.groupstudy.com/list/cisco.html Report misconduct and Nondisclosure violations to [EMAIL PROTECTED]
RE: Ping ethernet interface with datagram over 150 [7:63085]
Hello Priscilla, Thank you very much for your feedback! I am yet to try the protocol analyzer... mostly because I don:t have one. But I DO have a sort of packet sniffer, maybe I can find out something with that. Debug command, I think I need somebody on the other side to send me ping packets while I run the debug command to see what:s happening. I am not sure how much time they (the other company) are willing to spend on this. BTW, there is no firewall between the interfaces. However, there is an ATM TA on my side that converts ATM to Ethernet, which then, comes to my core router. The ATM TA also has an IP address, and the interface of this TA is set not to respond to ping packets over ethernet mtu. (it won:t fragment). However, as far as through-traffic is concerned, the TA does not put any limitation. So I think it's hard to conclude that the TA can be contributng to this problem. Sean Priscilla Oppenheimer wrote: > > Someone said "Think MTU," but I would say "Think IP > Fragmentation and Reassembly." :) In other words, different > MTUs isn't supposed to cause a problem for IP. > > However, your partner company could be sending pings with the > Don't Fragment bit set, in which case it would fail, if there > really is an MTU issue. > > See additional comment below. > > Sean Kim wrote: > > > > Hello, > > > > My company has this 3rd party connection through ATM. The ATM > > TA has an ethernet outlet which is and connected to our core > > router. Our parner company is connected with anATM module on > > their router. > > > > Recently, I was told by our partner company that they were > > running ping test and they could not ping my ethernet > interface > > (on the core router) with datagram over 1500 byte. > > > > From both the router itself and my workstation, I pinged my > own > > interface with 1600 byte, and I was able to ping it. But when > > I pinged my partner company's interface with 1600 byte, it > > failed. > > Well, this points to your partner's interface being the > problem. > > Ping should reply with the same payload it received. With a > large payload that needs to be broken up, problems could occur > with either the request or reply. It sounds like the problems > occur with the request when the partner pings and with the > replies when you ping the partner. The "debug ip icmp" command > might help you figure out what is happening. A protocol > analyzer would help too. > > By the way, many firewalls are set to not allow IP fragments, > since there's all sorts of evil things you can do with them. > Check for the existance of firewalls, including any personal > firewalls on the testing machines. > > Good luck with it. Keep us posted! Thanks, > > ___ > > Priscilla Oppenheimer > www.troubleshootingnetworks.com > www.priscilla.com > > > > > In general it seems that pinging from other nodes, there is no > > problem, but sitting on the routers itself, pinging the other > > routers interface with the datagram size of over 1500 is > failing. > > > > There isn't any problem with connection of performance. But I > > am very curious about why this is happening. > > Does anybody have any idea why this would happen? Or can > > anybody give me a clue as to how to approach this problem? > > > > Thank you in advance. > > > > Sean Kim > > > > > > Message Posted at: http://www.groupstudy.com/form/read.php?f=7&i=63465&t=63085 -- FAQ, list archives, and subscription info: http://www.groupstudy.com/list/cisco.html Report misconduct and Nondisclosure violations to [EMAIL PROTECTED]
