Re: MTU size in z/Linux
On Tue, Nov 15, 2011 at 11:43 AM, Agblad Tore wrote: > Hi, I just read some info about jumbo frames on a swedish it magazine site. > You need to have all equipment in the same net-segment support jumboframes. > As soon as it goes via a router (gateway) it will be re-packed to whatever > the other side supports. Hej, Tore. Right. I think the OP reported that once their switches had it enabled, the elephants could fly ;-) It's not always a good thing to fragment in the middle. Path MTU Discovery tries to avoid that. Rob -- For LINUX-390 subscribe / signoff / archive access instructions, send email to lists...@vm.marist.edu with the message: INFO LINUX-390 or visit http://www.marist.edu/htbin/wlvindex?LINUX-390 -- For more information on Linux on System z, visit http://wiki.linuxvm.org/
Re: MTU size in z/Linux
Hi, I just read some info about jumbo frames on a swedish it magazine site. You need to have all equipment in the same net-segment support jumboframes. As soon as it goes via a router (gateway) it will be re-packed to whatever the other side supports. So I guess it will work if all your zLinux servers within the same vlan supports jumboframes. I'm not an expert here, maybe someone else can verify. /Tore _ Tore Agblad System programmer, Volvo IT certified IT Architect Volvo Information Technology Infrastructure Mainframe Design & Development, Linux servers Dept 4352 DA1S SE-405 08, Gothenburg Sweden Telephone: +46-31-3233569 E-mail: tore.agb...@volvo.com http://www.volvo.com/volvoit/global/en-gb/ -Original Message- From: Linux on 390 Port [mailto:LINUX-390@VM.MARIST.EDU] On Behalf Of Martin, Terry R. (CMS/CTR) (CTR) Sent: den 10 november 2011 13:54 To: LINUX-390@VM.MARIST.EDU Subject: Re: MTU size in z/Linux Hi Thanks. After researching I found that the default MTU size on the 10G OSA is 8992. So trying at 9000 or anything higher than the 8992 on z/Linux is a moot point. Thanks again for the information. Btw, there was nothing that I had to do from the z/VM standpoint or TCP/IP on z/VM. The TCP/IP stack on the z/Linux guest is where the MTU size was set for this. The main thing in our case was that the Jumbo Frame support on our CISCO switch was not enabled once that was enabled we were able to start transferring Jumbo Frames. Thank You, Terry Martin Principal Systems Engineer Lockheed Martin CMS - CITIC 3300 Lord Baltimore Drive, Suite 200, 21244 Engineering Computing Mainframe Support Cell - 443 632-4191 -Original Message- From: Linux on 390 Port [mailto:LINUX-390@VM.MARIST.EDU] On Behalf Of Ursula Braun Sent: Thursday, November 10, 2011 3:30 AM To: LINUX-390@VM.MARIST.EDU Subject: Re: MTU size in z/Linux Terry, when changing the MTU value for a qeth device, the qeth driver does some checking against the the maximum value allowed. This value depends on the type of the qeth device (OSA or HiperSockets), but in both cases the hardware / firmware defines the maximum allowed value. Regards, Ursula Braun, IBM Germany On Wed, 2011-11-09 at 12:28 -0500, Martin, Terry R. (CMS/CTR) (CTR) wrote: > Hi > > It does not seem to let us specify an MTU higher than 8192. The > question is can we specify a MTU size of 9000 or 9200 > > Thank You, > > Terry Martin > Principal Systems Engineer > Lockheed Martin > CMS - CITIC > 3300 Lord Baltimore Drive, Suite 200, 21244 Engineering Computing > Mainframe Support Cell - 443 632-4191 -- For LINUX-390 subscribe / signoff / archive access instructions, send email to lists...@vm.marist.edu with the message: INFO LINUX-390 or visit http://www.marist.edu/htbin/wlvindex?LINUX-390 -- For more information on Linux on System z, visit http://wiki.linuxvm.org/
Re: MTU size in z/Linux
On Thursday, 11/10/2011 at 07:54 EST, "Martin, Terry R. (CMS/CTR) (CTR)" wrote: > Thanks. After researching I found that the default MTU size on the 10G OSA is > 8992. So trying at 9000 or anything higher than the 8992 on z/Linux is a moot > point. > > Thanks again for the information. > > Btw, there was nothing that I had to do from the z/VM standpoint or TCP/IP on > z/VM. The TCP/IP stack on the z/Linux guest is where the MTU size was set for > this. The main thing in our case was that the Jumbo Frame support on our CISCO > switch was not enabled once that was enabled we were able to start transferring > Jumbo Frames. The limit of 8992 is because the OSAs support 802.2/802.3x-conformant ethernet frames. (The 8992 value is documented in the OSA-Express Customer's Guide and Reference.) Alan Altmark Senior Managing z/VM and Linux Consultant IBM System Lab Services and Training ibm.com/systems/services/labservices office: 607.429.3323 mobile; 607.321.7556 alan_altm...@us.ibm.com IBM Endicott -- For LINUX-390 subscribe / signoff / archive access instructions, send email to lists...@vm.marist.edu with the message: INFO LINUX-390 or visit http://www.marist.edu/htbin/wlvindex?LINUX-390 -- For more information on Linux on System z, visit http://wiki.linuxvm.org/
Re: MTU size in z/Linux
Hi Thanks. After researching I found that the default MTU size on the 10G OSA is 8992. So trying at 9000 or anything higher than the 8992 on z/Linux is a moot point. Thanks again for the information. Btw, there was nothing that I had to do from the z/VM standpoint or TCP/IP on z/VM. The TCP/IP stack on the z/Linux guest is where the MTU size was set for this. The main thing in our case was that the Jumbo Frame support on our CISCO switch was not enabled once that was enabled we were able to start transferring Jumbo Frames. Thank You, Terry Martin Principal Systems Engineer Lockheed Martin CMS - CITIC 3300 Lord Baltimore Drive, Suite 200, 21244 Engineering Computing Mainframe Support Cell - 443 632-4191 -Original Message- From: Linux on 390 Port [mailto:LINUX-390@VM.MARIST.EDU] On Behalf Of Ursula Braun Sent: Thursday, November 10, 2011 3:30 AM To: LINUX-390@VM.MARIST.EDU Subject: Re: MTU size in z/Linux Terry, when changing the MTU value for a qeth device, the qeth driver does some checking against the the maximum value allowed. This value depends on the type of the qeth device (OSA or HiperSockets), but in both cases the hardware / firmware defines the maximum allowed value. Regards, Ursula Braun, IBM Germany On Wed, 2011-11-09 at 12:28 -0500, Martin, Terry R. (CMS/CTR) (CTR) wrote: > Hi > > It does not seem to let us specify an MTU higher than 8192. The > question is can we specify a MTU size of 9000 or 9200 > > Thank You, > > Terry Martin > Principal Systems Engineer > Lockheed Martin > CMS - CITIC > 3300 Lord Baltimore Drive, Suite 200, 21244 Engineering Computing > Mainframe Support Cell - 443 632-4191 -- For LINUX-390 subscribe / signoff / archive access instructions, send email to lists...@vm.marist.edu with the message: INFO LINUX-390 or visit http://www.marist.edu/htbin/wlvindex?LINUX-390 -- For more information on Linux on System z, visit http://wiki.linuxvm.org/
Re: MTU size in z/Linux
Terry, when changing the MTU value for a qeth device, the qeth driver does some checking against the the maximum value allowed. This value depends on the type of the qeth device (OSA or HiperSockets), but in both cases the hardware / firmware defines the maximum allowed value. Regards, Ursula Braun, IBM Germany On Wed, 2011-11-09 at 12:28 -0500, Martin, Terry R. (CMS/CTR) (CTR) wrote: > Hi > > It does not seem to let us specify an MTU higher than 8192. The question is > can we specify a MTU size of 9000 or 9200 > > Thank You, > > Terry Martin > Principal Systems Engineer > Lockheed Martin > CMS - CITIC > 3300 Lord Baltimore Drive, Suite 200, 21244 > Engineering Computing > Mainframe Support > Cell - 443 632-4191 -- For LINUX-390 subscribe / signoff / archive access instructions, send email to lists...@vm.marist.edu with the message: INFO LINUX-390 or visit http://www.marist.edu/htbin/wlvindex?LINUX-390 -- For more information on Linux on System z, visit http://wiki.linuxvm.org/
Re: MTU size in z/Linux
Hi It does not seem to let us specify an MTU higher than 8192. The question is can we specify a MTU size of 9000 or 9200 Thank You, Terry Martin Principal Systems Engineer Lockheed Martin CMS - CITIC 3300 Lord Baltimore Drive, Suite 200, 21244 Engineering Computing Mainframe Support Cell - 443 632-4191 -Original Message- From: Linux on 390 Port [mailto:LINUX-390@VM.MARIST.EDU] On Behalf Of Richard Gasiorowski Sent: Wednesday, November 09, 2011 12:17 PM To: LINUX-390@VM.MARIST.EDU Subject: Re: MTU size in z/Linux change it in /etc/sysconfig/network-scripts/ifcfg-ethx Richard (Gaz) Gasiorowski Solution Architect CSC 3170 Fairview Park Dr., Falls Church, VA 22042 845-889-8533|Work|845-392-7889 Cell|rgasi...@csc.com|www.csc.com This is a PRIVATE message. If you are not the intended recipient, please delete without copying and kindly advise us by e-mail of the mistake in delivery. NOTE: Regardless of content, this e-mail shall not operate to bind CSC to any order or other contract unless pursuant to explicit written agreement or government initiative expressly permitting the use of e-mail for such purpose. From: "Martin, Terry R. (CMS/CTR) (CTR)" To: LINUX-390@vm.marist.edu Date: 11/09/2011 11:58 AM Subject: MTU size in z/Linux Hi Can we set a custom MTU size in z/Linux RHEL 5.2. We would like to set the MTU to 9000 but can't seem to get it to take? The network switch we are communication with supports a MAX MTU of 9216. Thank You, Terry Martin Principal Systems Engineer Lockheed Martin CMS - CITIC 3300 Lord Baltimore Drive, Suite 200, 21244 Engineering Computing Mainframe Support Cell - 443 632-4191 -- For LINUX-390 subscribe / signoff / archive access instructions, send email to lists...@vm.marist.edu with the message: INFO LINUX-390 or visit http://www.marist.edu/htbin/wlvindex?LINUX-390 -- For more information on Linux on System z, visit http://wiki.linuxvm.org/ -- For LINUX-390 subscribe / signoff / archive access instructions, send email to lists...@vm.marist.edu with the message: INFO LINUX-390 or visit http://www.marist.edu/htbin/wlvindex?LINUX-390 -- For more information on Linux on System z, visit http://wiki.linuxvm.org/ -- For LINUX-390 subscribe / signoff / archive access instructions, send email to lists...@vm.marist.edu with the message: INFO LINUX-390 or visit http://www.marist.edu/htbin/wlvindex?LINUX-390 -- For more information on Linux on System z, visit http://wiki.linuxvm.org/
Re: MTU size in z/Linux
change it in /etc/sysconfig/network-scripts/ifcfg-ethx Richard (Gaz) Gasiorowski Solution Architect CSC 3170 Fairview Park Dr., Falls Church, VA 22042 845-889-8533|Work|845-392-7889 Cell|rgasi...@csc.com|www.csc.com This is a PRIVATE message. If you are not the intended recipient, please delete without copying and kindly advise us by e-mail of the mistake in delivery. NOTE: Regardless of content, this e-mail shall not operate to bind CSC to any order or other contract unless pursuant to explicit written agreement or government initiative expressly permitting the use of e-mail for such purpose. From: "Martin, Terry R. (CMS/CTR) (CTR)" To: LINUX-390@vm.marist.edu Date: 11/09/2011 11:58 AM Subject: MTU size in z/Linux Hi Can we set a custom MTU size in z/Linux RHEL 5.2. We would like to set the MTU to 9000 but can't seem to get it to take? The network switch we are communication with supports a MAX MTU of 9216. Thank You, Terry Martin Principal Systems Engineer Lockheed Martin CMS - CITIC 3300 Lord Baltimore Drive, Suite 200, 21244 Engineering Computing Mainframe Support Cell - 443 632-4191 -- For LINUX-390 subscribe / signoff / archive access instructions, send email to lists...@vm.marist.edu with the message: INFO LINUX-390 or visit http://www.marist.edu/htbin/wlvindex?LINUX-390 -- For more information on Linux on System z, visit http://wiki.linuxvm.org/ -- For LINUX-390 subscribe / signoff / archive access instructions, send email to lists...@vm.marist.edu with the message: INFO LINUX-390 or visit http://www.marist.edu/htbin/wlvindex?LINUX-390 -- For more information on Linux on System z, visit http://wiki.linuxvm.org/
MTU size in z/Linux
Hi Can we set a custom MTU size in z/Linux RHEL 5.2. We would like to set the MTU to 9000 but can't seem to get it to take? The network switch we are communication with supports a MAX MTU of 9216. Thank You, Terry Martin Principal Systems Engineer Lockheed Martin CMS - CITIC 3300 Lord Baltimore Drive, Suite 200, 21244 Engineering Computing Mainframe Support Cell - 443 632-4191 -- For LINUX-390 subscribe / signoff / archive access instructions, send email to lists...@vm.marist.edu with the message: INFO LINUX-390 or visit http://www.marist.edu/htbin/wlvindex?LINUX-390 -- For more information on Linux on System z, visit http://wiki.linuxvm.org/
