Increase Cent. OS 7s MTU Geek Projects. Ethernet interfaces normally use an MTU of 1. I recently needed to increase the MTU use by the NICs on a point to point link to 9. DRBD performance. This is sometimes referred to as enabling jumbo frames. Native memory allocation mmap failed to map XX bytes for committing reserved memory JDK 1. 8 CentOS 6. 7. October 5, 2015 CentOS 6 0 Comments. VPSWordPress. http 1. 1 Linux. LinuxUnix. In the past Ive used ifconfig to test this change out. For example, to increase the MTU of the eth. I would runifconfig eth. I could then verify that the new MTU had been applied by running ifconfig eth. Unfortunately for me the two servers that I was working on, like many Cent. OS 7 systems did not have the ifconfig command installed. If you want the ifconfig command, then you can install it by installing the net tools package yum install net tools. However, I wanted to avoid making any changes other than increasing the MTU, so I use the ip command instead. The ip command can be used in place of ifconfig for many purposes, including increasing the MTU. For example, to increase the MTU of the eth. You can then verify that the new MTU has taken effect by running ip link show dev eth. After youve applied the new MTU, and verified that all is working as expected, be sure to update the interfaces configuration file, so that this change persists the next time the server is rebooted. To edit the MTU for the eth. MTU line to the etcsysconfignetwork scriptsifcfg eth. For example MTU9. Cent. OS RHEL 7 How to disable IPv. Post describes procedure to disable IPv. Cent. OSRHEL 7. There are 2 ways to do this 1. Disable IPv. 6 in kernel module requires reboot2. Disable IPv. 6 using sysctl settings no reboot requiredTo verify if IPv. Disable IPv. 6 in kernel module requires reboot1. Edit etcdefaultgrub and add ipv. GRUBCMDLINELINUX, e. GRUBDEFAULTsaved. GRUBDISABLESUBMENUtrue. GRUBTERMINALOUTPUTconsole. GRUBCMDLINELINUXipv. GRUBDISABLERECOVERYtrue2. Regenerate a GRUB configuration file and overwrite existing one grub. Restart system and verify no line inet. Disable IPv. 6 using sysctl settings no reboot required1. Append below lines in etcsysctl. NOTE To disable IPv. To make the settings affective, execute NOTE make sure the file etcsshsshdconfig contains the line Address. Family inet to avoid breaking SSH Xforwarding if you are using the sysctl method. Add the Address. Family line to sshdconfig vi etcsshsshdconfig. Address. Family inet. Restart sshd for changes to get get effect.