如何永久更改MTU设置

Question

我想永久改变MTU来1500.通过永久我的意思是,如果我重新启动系统还是会做service network restart它总是支持1500.

我按照这篇文章http://www.cyberciti.biz/faq/centos-rhel-redhat-fedora-debian-linux-mtu-size/

但不幸的是,它对我不起作用.

这是我做的:

检查当前MTU:

eth0: <BROADCAST,MULTICAST,UP,LOWER_UP> mtu 9001 qdisc pfifo_fast state UP qlen 1000 

添加MTU="1500"到/etc/sysconfig/network-scripts/ifcfg-eth0:

[root@ip-xx-xx-xxx~]# cat /etc/sysconfig/network-scripts/ifcfg-eth0
DEVICE=eth0
BOOTPROTO=dhcp
ONBOOT=yes
TYPE=Ethernet
USERCTL=yes
PEERDNS=yes
IPV6INIT=no
PERSISTENT_DHCLIENT=yes
IPV6_MTU="1500"
MTU="1500"

然后MTU再次检查,(没有运气):

root@ip-xx-xx-xxx ~]# service network restart 
Shutting down interface eth0:                              [  OK  ]
Shutting down loopback interface:                          [  OK  ]
Bringing up loopback interface:                            [  OK  ]
Bringing up interface eth0:  
Determining IP information for eth0... done.
                                                           [  OK  ]
[root@ip-xx-xx-xxx ~]# ip addr show eth0 
2: eth0: <BROADCAST,MULTICAST,UP,LOWER_UP> mtu 9001 qdisc pfifo_fast state UP qlen 1000

/sbin/ifconfig改变了MTU但只是暂时的

[root@ip-xx-xx-xxx ~]# /sbin/ifconfig eth0 mtu 1500 up
[root@ip-xx-xx-xxx ~]# ip addr show eth0 
2: eth0: <BROADCAST,MULTICAST,UP,LOWER_UP> mtu 1500 qdisc pfifo_fast state UP qlen 1000

如果我重新启动network它再次是9001:

[root@ip-xx-xx-xxx ~]# service network restart 
Shutting down interface eth0:                              [  OK  ]
Shutting down loopback interface:                          [  OK  ]
Bringing up loopback interface:                            [  OK  ]
Bringing up interface eth0:  
Determining IP information for eth0... done.
                                                           [  OK  ]
[root@ip-10-0-1-135 ~]# ip addr show eth0 
2: eth0: <BROADCAST,MULTICAST,UP,LOWER_UP> mtu 9001 qdisc pfifo_fast state UP qlen 1000

Answer 1

您的环境中的MTU是通过DHCP自动设置的,在您的配置中您具有以下设置:

DEVICE=eth0

BOOTPROTO=dhcp

所以DHCP实际上是设置MTU大小.在Ubuntu中,您可以编辑以下文件:/etc/dhcp/dhclient.conf

在请求行之前设置这两个命令:

default interface-mtu 1500;

supercede interface-mtu 1500;

我不知道如何在Red Hat中设置它,但我认为该文件被调用 dhcpd.conf

希望这可以帮助!