Please can someone translate this Cisco doc for me?

[Dieselboy]

I am more confused after reading this doc compared to before reading the doc.

Ref: https://www.cisco.com/c/en/us/td/docs/switches/lan/catalyst3650/software/release/3se/int_hw_components/configuration_guide/b_int_3se_3650_cg/b_int_3se_3650_cg_chapter_0110.html

Screenshot added to explain.

FYI - there is no such command "system mtu jumbo xxxx" and the command does look like it worked on the 10GB ports: "system mtu 9198"

[Otanx]

I am confused too. So I looked at a 3850 we have. Should be pretty close to 3650. We have the "system mtu 9100" command, and that is it. Doing a "show int te1/1/1 mtu" I get 9100 bytes in the output. Looking at interface configs the "ip mtu" command does not exist when configured as a switchport, but does if configured as a L3 interface. We do not have ip mtu configured on any interfaces, and it does show the MTU of 9100 bytes in a "show int mtu" for both L2 and L3 ports.

I do not have a "system mtu jumbo" command. Just "system mtu". Doing a "show system mtu" gives me "Global Ethernet MTU is 9100 bytes" Everything looks like it should be 9100. Lets do some testing...

I have three switches. Two 3850s and a 6500 connected in a row...  3850----3850----6500

Testing from the end 3850:
ping 10.10.10.10 size 9000 df
!!!!!

So that works. 10.10.10.10 is the 6500 interface to the middle 3850.

ping 10.10.10.20 size 9000 df
M.M.M

Hmmm, that didn't work. 10.10.10.20 is the loopback of the 6500. Lets try something else.

ping 10.10.10.5 size 9000 df
!!!!!

That is the interface I am connected to on the middle 3850.

ping 10.10.10.22 size 9000 df
M.M.M

Loopback of the middle 3850.

show int lo0 | in MTU
MTU 1514 bytes

hmmm. Lets try one more thing.

ping 10.10.10.10 size 9000 df source lo0
!!!!!

!? So I can send from lo0 with a 9000 MTU, but it will not accept packets with a larger MTU.

This is prod so I can't make changes, but I am guessing I need the ip mtu 9100 command on the loopback for it to fully work.

-Otanx

[icecream-guy]

I was going to do that arf arf woof woof gag again,

but here is Estonian

Süsteemi MTU väärtused

Konfigureerida saab järgmisi MTU väärtusi:

    Süsteem MTU - See väärtus kehtib lülitite Gigabit Etherneti ja 10-Gigabit Etherneti pordipakettide kohta. Süsteemi jumbo MTU väärtuse määramiseks kasutage süsteemi mtu bytes globaalset konfiguratsiooni käsku.

    Süsteem Jumbo MTU - See väärtus kehtib lülitite Gigabit Etherneti ja 10-Gigabit Etherneti pordipakettide kohta. Kasutage süsteemi mtu jumbo bytes globaalset konfiguratsiooni käsku, et määrata süsteemi jumbo MTU väärtus.

    Protokollispetsiifiline MTU - see väärtus kehtib ainult marsruutitud pakettidele lüliti või lüliti stacki kõigis marsruutitud pordides. Protokolli-spetsiifilise MTU väärtuse määramiseks kasutage ip mtu baiti või ipv6 mtu bytes liidese konfiguratsiooni käsku.

or Malagasy

System MTU Values

Ireto manaraka ireto ny soatoavin'ny MTU:

    System MTU - Ity lanjany ity dia mihatra amin'ny poketrany mihidy ao amin'ny Gigabit Ethernet sy 10-Gigabit Ethernet port of the switch. Ampiasao ny baikom-pifandraisana mtu bytes an'ny rafitra mba hanondroana ny mari-pamantarana momban'ny MTU.

    System Jumbo MTU - Ity lanjany ity dia mihatra amin'ny poketrany mihidy ao amin'ny Gigabit Ethernet sy 10-Gigabit Ethernet port of the switch. Ampiasao ny baikom-pifandraisana mtu jumbo bytes manondro ny mari-pamantarana momban'ny MTU.

    Protaka-manokana MTU - Ity sanda ity dia ampiharina amin'ny sora-baventy voapetaka eo amin'ny sehatra voapetaka amin'ny fikandrana na kitapo fisakanana. Ampiasao ny baiko fanamafisana IP mtu na ipv6 mtu bytes ny baiko fampifanarahana mba hamaritra ny mari-pamantarana MTU.

[Dieselboy]

Thanks Ristau 

Otanx, I just done the same as you - set the system mtu command and then done a show interface before and afterwards. Indeed the mtu on the interface does reflect the change.
Are your ping tests that are failing due to trying to route 9000-bytes ?

I'm wanting to increase the mtu as this switch connects to a SAN on 10gb ports. I still need to look at the buffer allocations for this.

[Otanx]

I think the failures are because the system mtu command is not applied to the loopback interface. When I do a show int lo0 I get the MTU being 1514 instead of 9100. So if my ping destination is the loopback it drops the packet. I think to fix this you would need the ip mtu command on the loopback interface however I am not worried as the device handles forwarding of jumbo frames, and I don't really care too much if the management of the device is limited to 1500.

-Otanx

[Dieselboy]

Thanks for the support on this

[deanwebb]

On a side note, my brother learned Estonian and I have a friend in Madagascar. INSANE languages, the both of them!