How change NIC MTU to 9000?

[JKnott]

@tim-mcmanus said in How change NIC MTU to 9000?:

If it's a bunch of web traffic or messages between systems, do you really need a high MTU? Even database traffic should be scrutinized to determine whether or not you're moving significant chunks of data between servers. It could be tiny bits of data.

The thing about MTU is it means maximum size. It doesn't say you can't send smaller. In fact the smallest supported frame has a payload of 46 bytes. With Ethernet and IP, you can use whatever packet size is appropriate for the data. So, if you're sitting at a keyboard, connected via ssh, you will be sending out a lot of very small packets. But there is nothing to stop those small packets from sharing a network with those huge packets in the data centre. The advantage of the large packets is better performance with large amounts of data, be it in routers or end computers.

A few years ago, I was reading an article about that CERN accelerator, where that Higgs bosson was discovered. Due to the huge amounts of data being shipped around the world, they were using jumbo frames over very high speed links. So, there's no technical reason why IP with 9000 byte MTU couldn't eventually be made available on the Internet. The hardware supports it now and has for several years.

[JKnott]

Incidentally, here's something about a research network in Ontario, called "Orion". It's part of the CANARIE network that connects Canada and is in turn connected to similar networks around the world. This is a second Internet that is built to support up to 9000 MTU.

[JKnott]

@jknott said in How change NIC MTU to 9000?:

The trend is to not fragment. That's manatory on IPv6 and IPv4 is moving that way. If the DF flag is set, the router is supposed to send an ICMP error message back to the source, specifying the maximum supported MTU.

One thing I've noticed is Linux sets DF for TCP, UDP and ICMP. Windows only does for TCP.

[yon 0]

@tim-mcmanus said in How change NIC MTU to 9000?:

如果它是系统之间的一堆网络流量或消息，你真的需要高MTU吗？应仔细检查数据库流量，以确定您是否在服务器之间移动了大量数据。它可能是微小的数

ubuntu can easy setup it, but i don't know the Pfsense how do it. i use these server for BGP transit, so need fast network

and by the way, i have test setup the txqueuelen 10000 config, helpful fast network speed. test in ubuntu and openvpn.

but the pfsense has like this txqueuelen setup ?

[stephenw10]

So what have you tried that doesn't work? You should just be able to set the interface MTU in the gui.

Steve

[JKnott]

I just tried setting the MTU in the GUI and found it works. Here's what ifconfig shows for the interface before I changed it:

em0: flags=8843<UP,BROADCAST,RUNNING,SIMPLEX,MULTICAST> metric 0 mtu 1500
options=209b<RXCSUM,TXCSUM,VLAN_MTU,VLAN_HWTAGGING,VLAN_HWCSUM,WOL_MAGIC>
ether 90:e2:ba:4d:d6:b3
hwaddr 90:e2:ba:4d:d6:b3
inet6 fe80::92e2:baff:fe4d:d6b3%em0 prefixlen 64 scopeid 0x2
inet6 fd48:1a37:2160:4::1 prefixlen 64
inet 172.16.4.1 netmask 0xffffff00 broadcast 172.16.4.255
nd6 options=21<PERFORMNUD,AUTO_LINKLOCAL>
media: Ethernet autoselect
status: no carrier

And after

em0: flags=8843<UP,BROADCAST,RUNNING,SIMPLEX,MULTICAST> metric 0 mtu 9000
options=209b<RXCSUM,TXCSUM,VLAN_MTU,VLAN_HWTAGGING,VLAN_HWCSUM,WOL_MAGIC>
ether 90:e2:ba:4d:d6:b3
hwaddr 90:e2:ba:4d:d6:b3
inet6 fe80::92e2:baff:fe4d:d6b3%em0 prefixlen 64 scopeid 0x2
inet6 fd48:1a37:2160:4::1 prefixlen 64
inet 172.16.4.1 netmask 0xffffff00 broadcast 172.16.4.255
nd6 options=21<PERFORMNUD,AUTO_LINKLOCAL>
media: Ethernet autoselect
status: no carrier

As you can see, the MTU changed from 1500 to 9000.

[yon 0]

@jknott ..

i have try setup in interfaces.php?if=opt3 but it not work. still MTU is 1500

[stephenw10]

Ok, we are going to need to see the opt3 config section and the ifconfig output for that interface. And any logs you have showing the change or any errors.

Steve

[yon 0]

@stephenw10

now i have try setup LAN nic change to MTU 9000, but still show 1500 MTU no log show.

[Grimson]

From the FreeBSD manual at: https://www.freebsd.org/cgi/man.cgi?query=re&sektion=4&manpath=FreeBSD+11.1-RELEASE

The 8169, 8169S and 8110S also support jumbo frames, which can be configured via the interface MTU setting. The MTU is limited to 7422, since the chip cannot transmit larger frames. Selecting an MTU larger than 1500 bytes with the ifconfig(8) utility configures the adapter to receive and transmit jumbo frames.

So check what kind specific Realtek chipset you have, but 9000 will simply not work with crappy hardware like this.

[yon 0]

@grimson

i have try intel NIC still the same wrong.

[stephenw10]

I would also guess an re issue there. Can you set the MTU from the CLI?:

[2.4.4-DEVELOPMENT][root@apu.stevew.lan]/root: ifconfig re2 mtu 9000
[2.4.4-DEVELOPMENT][root@apu.stevew.lan]/root: ifconfig re2
re2: flags=8943<UP,BROADCAST,RUNNING,PROMISC,SIMPLEX,MULTICAST> metric 0 mtu 9000
	options=82098<VLAN_MTU,VLAN_HWTAGGING,VLAN_HWCSUM,WOL_MAGIC,LINKSTATE>
	ether 00:0d:b9:37:30:12
	hwaddr 00:0d:b9:37:30:12
	inet 192.168.35.1 netmask 0xffffff00 broadcast 192.168.35.255 
	inet 19.168.35.254 netmask 0xffffff00 broadcast 19.168.35.255 vhid 1 
	inet6 fe80::1:1%re2 prefixlen 64 scopeid 0x3 
	nd6 options=21<PERFORMNUD,AUTO_LINKLOCAL>
	media: Ethernet autoselect (none)
	status: no carrier
	carp: INIT vhid 1 advbase 1 advskew 0

Steve

[yon 0]

i had try do that before, now i have upgrade PF 2.4.3 to 2.4.4, but i can't open lan gateway webGUI, i can ping gateway ip and network work, why i can't open webGUI. i need waiting for fix this and then try setup MTU again.