Hi,
I have RB4011GS+ and I have on all ports and VLANs set the L2MTU on Max size and then on needed ports and VLANs set the MTU size to jumbo - 9000, but not at all.
I have two ports configured as Tagged Trunk ports with MTU for Jumbo frames.
I dont know what should I set now and how do that, that I have all VLANs (with and without jumbo frames) in this two Trunk ports and will work together and will also use the jumbo frames as needed.
Thanks for help.
Jumbo frames in practice are only effective for local traffic, i.e. usually only for switching.
You cannot enforce jumbo frames, only allow them. So in addition to what you did in teh RB4011, you also have to do that in all connected devices.
Hi,
yes I know it and I need to allow it while I have 3v VLANs where are devices that need to have allowed jumbo frames, have complete route path and I need all forward over 2 trunk ports to switches where are connected these devices.
I’m only unsure if when I enable jumbo frames is possible to have all ports in one bridge, while some ports and vans doesn’t use jumbo and also are forwarded over the trunk ports too.
Thanks.
There may be something lost in translation. Perhaps use a translation service (Google Translate, DeepL), to allow you to compose your question/response in your own native language and then translate, and finally paste both the original language and the machine translation into the post.
All devices on a specific LAN (or vlan) should be using the same IP/Layer-3/L3 MTU. If that isn't the case, then it will cause problems.
If your question was "Can I have a single trunk port that is carrying vlans that use different L3 MTUs?", then the answer is yes. You need to make sure that the L2MTU is set high enough for the largest, and this may "waste" some memory for buffers on the switch. The L2MTU sized buffers, and the buffers have to be large enough for the largest possible packet. If you can understand spoken English, this may be helpful VLANs, pt.3: QinQ and the L2MTU mystery
Be aware that sharing a trunk with storage servers and time sensitive traffic isn't recommended, but it will work, but small packets will be delayed longer.
You don't specify what the "devices that need to have jumbo frames" are. Ideally you would dedicate trunk links for those devices, possibly even separate switches. You can alway try without dedicated hardware and see if thing work well enough before deciding to dedicate hardware.
Hi @Buckeye ,
thanks, I know that I can’t mix in one vlan with different MTUs. Therefor I have for each purpose a different VLAN, while I need 3 VLANs with Jumbo frames for special purposes for virtualisation and all others are with normal MTU, work standard workloads and users.
But I had problem if I can use for all these VLANs one bridge while I need all these VLANs with and without a Jumbo Frames to transfer over Trunk ports to the switches to deliver it to needed devices and I have found and also get many different answers. But as I see from your answer this will be the way, while other wise I can’t get all needed to one trunk port when I have it in different bridges.
I still try to learn the logic of the Mikrotik while its different from other vendors like Dell, Cisco or others ..
Thanks.
I don't have an RB4011, but it has two switch chips, so I think to get best performance you would create bridge devices, but each bridge only having bridge-ports in the same switch. Then split the vlans over the two bridges. You can still call your vlan interfaces anything you want, but note that it would be possible to create a br0.99 vlan interface off the bridge on switch0 and br1.99 on switch1, and these would be two different interfaces, both using the same tag (and within the RB4011 would be separate, but if you plugged both into the same external switch, the two vlans would commingle into a single vlan99 on the external switch, so best practice would be to use different vlans on the RB4011 to avoid that problem.
Here is output from an RB760iGS. But I don't use Jumbo frames.
[demo@MikroTik] > /interface/print
Flags: R - RUNNING; S - SLAVE
Columns: NAME, TYPE, ACTUAL-MTU, L2MTU, MAX-L2MTU, MAC-ADDRESS
# NAME TYPE ACTUAL-MTU L2MTU MAX-L2MTU MAC-ADDRESS
0 ether1 ether 1500 1596 2026 DC:2B:AD:4D:EC:F1
1 RS ether2 ether 1500 1596 2026 DC:2B:AD:4D:EC:F2
2 ether3 ether 1500 1596 2026 DC:2B:AD:4D:EC:F3
3 R ether4 ether 1500 1596 2026 DC:2B:AD:4D:EC:F4
4 RS ether5 ether 1500 1596 2026 DC:2B:AD:4D:EC:F5
5 S sfp1 ether 1500 1596 2026 DC:2B:AD:4D:EC:F6
6 R br.199 vlan 1500 1592 DC:2B:AD:4D:EC:F2
7 R br.200 vlan 1500 1592 DC:2B:AD:4D:EC:F2
8 R br.210 vlan 1500 1592 DC:2B:AD:4D:EC:F2
9 R br.999 vlan 1500 1592 DC:2B:AD:4D:EC:F2
10 R bridge bridge 1500 1596 DC:2B:AD:4D:EC:F2
11 R lo loopback 65536 00:00:00:00:00:00
The MT7621 (in the RB760iGS) doesn't support large jumbo frames, it's MAX-L2MTU is 2026.
Note the L2MTU has to be larger than the ACTUAL-MTU (the L3 MTU) and can't be set higher than MAX-L2MTU. Also note that the 4 byte vlan headers come out of the L2MTU (note the L2MTU for the vlan interfaces (for example br.199) is 4 less than the L2MTU of the bridge device itself (that is untagged).
OK understand, the L2MTU should be smaller as MAX_L2MTU but bigger then Actual MTU and all can be in on bridge.
Thanks.
Note: What I showed from the RB760iGS were defaults. I didn't set anything for MTU.
The MT7621 will only support a max of 2026. It would be possible to set higher than the 1596 that is the default. The L2MTU is just like the size of the bucket you use to carry water. If you neet to transport 6 liters, you can use a 6 liter bucket, or you can use a larger one. But if you use a smaller one, then you will have to make multiple trips to transport 6 liters. Same with MTU. If it is low, it takes more packets to transport the same amount of data. But I am sure you know that, or you wouldn't be asking about jumbo frames.
The point I am trying to make is that if you set your L2MTU to MAX, when you create a vlan interface, the L2MTU on the vlan interace will be reduced by 4 bytes. So if you were setting your L3 MTU to 9000, then the L2MTU has to be larger than 9000 if you want to be able to use tagged vlans.
Also, you will need to verify that all your external switches support jumbo frame that are large enough. For example, you wouldn't be able to use an RB760iGS as a switch for 9000 L3 MTU frames.
And to extend the analogy: MTU is the amount of water the filler will pour. If you come with a smaller bucket (L2MTU on a particular device smaller than "global" setting), then water will overflow.
And then there's "processing plant" which can transfer water from buckets to bottles and vice versa (i.e. router). If it receives large bucket of water, it'll fill multiple small bottles (and send those further with courier which only handles bottles). If it receives bottles, it'll pour each one bottle to separate bucket (and let courier handling buckets to carry half-empty buckets to the destination).
Thanks