Notes TCP/IP Jumbo Frame Trame géante MTU

Voir :

Peut être utile pour du SAN / NAS :

Connaître la MTU d'une interface

netstat -i
ip link |grep mtu

Changer provisoirement la MTU d'une inferface

#ifconfig eth1 mtu 9000 up
ip link set eth1 mtu 9000

Changer la MTU sur RedHat

/etc/sysconfig/network-scripts/ifcfg-enp0s9

HWADDR=08:00:27:D9:8B:E7
TYPE=Ethernet
BOOTPROTO=none
IPADDR=192.168.25.21
PREFIX=24
DEFROUTE=yes
IPV4_FAILURE_FATAL=yes
IPV6INIT=no
NAME=enp0s9
UUID=5f82629e-5117-4d41-902d-090d82053cb2
ONBOOT=yes
MTU=9000

Changer la MTU sous RedHat avec NetworkManager

nmcli connection modify eno2 802-3-ethernet.mtu 9000
nmcli connection show eno2 |grep mtu

Changer la MTU d'une interface sur Debian

/etc/network/interfaces.d/eth1

auto eth1

iface eth1 inet static
        address 192.168.56.12
        netmask 255.255.255.0
        mtu 9000

Appliquer les changements

systemctl restart networking

Connaitre la MTU entre deux points

# traceroute --mtu 192.168.56.1

traceroute to 192.168.56.1 (192.168.56.1), 30 hops max, 65000 byte packets
 1  192.168.56.1 (192.168.56.1)  0.223 ms F=1500 *  0.446 ms

F=1500

Tester

1472 = 1500 - 28

Voir aussi /proc/sys/net/ipv4/ip_no_pmtu_disc

# ping -M do -s 1472 192.168.6.130
PING 192.168.6.130 (192.168.6.130) 1472(1500) bytes of data.
1480 bytes from 192.168.6.130: icmp_req=1 ttl=255 time=0.095 ms
1480 bytes from 192.168.6.130: icmp_req=2 ttl=255 time=0.127 ms
^C
--- 192.168.6.130 ping statistics ---
2 packets transmitted, 2 received, 0% packet loss, time 999ms
rtt min/avg/max/mdev = 0.095/0.111/0.127/0.016 ms

# ping -M do -s 1473 192.168.6.130
PING 192.168.6.130 (192.168.6.130) 1473(1501) bytes of data.
^C
--- 192.168.6.130 ping statistics ---
4 packets transmitted, 0 received, 100% packet loss, time 2999ms

Path MTUs are recorded in the routing cache. This can interfere with testing, and in particular, can make a remote MTU restriction appear to be a local one. You can clear the cache using the ip route command.

ip route flush cache