{{tag>Brouillon Réseau}} # Notes TCP/IP Jumbo Frame Trame géante MTU Voir : * [Jumbo Frame](https://fr.wikipedia.org/wiki/Trame_g%C3%A9ante) * http://www.microhowto.info/howto/change_the_mtu_of_a_network_interface.html Peut être utile pour du SAN / NAS : * [[Notes SAN iSCSI]] * [[Notes NFS]] Connaître la MTU d'une interface ~~~bash netstat -i ip link | grep mtu ~~~ Changer provisoirement la MTU d'une inferface ~~~bash #ifconfig eth1 mtu 9000 up ip link set eth1 mtu 9000 ~~~ Changer la MTU sur RedHat `/etc/sysconfig/network-scripts/ifcfg-enp0s9` ~~~ini 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 ~~~bash 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 ~~~bash 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. ~~~bash ip route flush cache ~~~