Enabling Jumbo frames on switches

[strelok]

Hello !

We have core level based on OmniSwitches 9000E and distriburion level based on OmniSwitch 6850.

Our colleagues who administrates servers whants to enable jumbo frames in network.

So, I would like to ask how to enable jumbo frames for OmniSwithes properly.

As I understand we have to enable jumbo frames at all switches in network.


Thank you in advance.

[silvio]

by default jumbo frames are enabled. You can check the long frame size:

Code: Select all

> show interfaces 1/23
 Slot/Port  1/23 :
  Operational Status     : up,
  Last Time Link Changed : THU FEB 04 18:54:58 ,
  Number of Status Change: 10,
  Type                   : Ethernet,
  SFP/XFP                : Not Present,
  MAC address            : e8:e7:32:28:f9:68,
  BandWidth (Megabits)   :     1000,            Duplex           : Full,
  Autonegotiation        :   1  [ 1000-F 100-F 100-H 10-F 10-H ],
  Long Frame Size(Bytes) : 9216,

Changing you can with
> interfaces 1/23 max frame ?


regards
Silvio

[strelok]

Hi silvio,

Thank you for response.

But when I try to make ping with frame more that 1500, I see following message:


Ping with standard size1472:

RS-1201-> ping 10.10.10.10 size 1472 dont-fragment

PING 10.10.10.10: 1472 data bytes
1480 bytes from 10.10.10.10: icmp_seq=0. time=1. ms
1480 bytes from 10.10.10.10: icmp_seq=1. time=9. ms
----10.10.10.10 PING Statistics----
2 packets transmitted, 2 packets received, 0% packet loss
round-trip (ms) min/avg/max = 1/5/9


And ping with packet size more than 1472 (1500):

RS-1201-> ping 10.10.10.10 size 1473 dont-fragment
ERROR: Data size greater than 1472 bytes (MTU 1500) not supported with dont-fragment set for ping

Does it mean that jumbo frames don't work ?

[silvio]

Have you checked frame size? it is different at ports with 100M/1G and 10G.
frame-size (jumbo) is at L2. If a frame within the same vlan will go through the switch this is the important value.
MTU is at L3. This is important for traffic that will be routed at the switch (or ping direct from the switch). The mtu size you can check direct at your ip interface (show ip interface if-100).
regards
Silvio

[Dierckek]

I have the impression that the error is coming from your Pc's OS. Normally spoken you would expect to see an ICMP Destination unreachable, code 4 (Fragmentation required, and DF flag set) -or plain timeout if ICMP messages are suppressed- if the switch does not support Jumbo frames.