Jumbo Frame in 6509

[jayshihlin]

Hi all,

Got couple questions regards to jumbo fame in the 6509.  I setup jumbo frame mtu in couple of interfaces on 6509. 

1.       I had WS-X6748-GE-TX in 6509.  When I go to interface config mode.  I can only configured as 9216 and nothing else.  I was thinking to set it up as 9000 since our server support upto 9000.

6509(config)#int gi4/1

6509(config-if)#mtu ?

  <9216-9216>  MTU size in bytes

6509(config-if)#mtu

2.       After configured interface with mtu 9216 and server to max mtu 9000, I am able to ping between the hosts with

Ping 192.168.1.1 –l 8972 –f which is good news.  So I cleared the counter and run show interface gi4/1 again, the count in “giants” start went up.  My question: is the giants counter in show interface a jumbo frame been transmitted or it’s a error giants frame that been drop by interface?

Thanks for reading the post and any comments are appreciated.

=J=

[kyukim · Accepted solution]

HI,

It is known behavior . Packet is not dropped but reported as giant.

You can take a look at below bug.

CSCek38622    Giant Frames Incorrectly Recorded on WS-X6748-GE-TX (Cosmetic)

Above DDTS fixed this behavior only on Trunk mode.

Giant counter from sh int and OverSizePkts from sh count int still increases on access port.

KK

[jayshihlin]

Hi KK,

Thanks for promptly reply.  The bug is fixed in 12.2(18)SXF11 but I am running 12.2(33)SXH6..  Also do you know why I can only use 9216 in interface config mode?  Why I can't use as range such as <1500 - 9216> ?

Thanks,

=J=

[kyukim]

Hi,
Bug is fixed only on TRUNK port, not on access port.

I saw same behavior on SXI2a with access port.

You can't change MTU on interface due to our design.

By default, jumbo frame support is enabled on 6748 and you can't change mtu on interface.

KK.  

[Reza Sharifi]

Hi KK,

When you say support is enabled, does it meant the MTU is already set to jumbo or it is adaptive, meaning it can go up to 9216?

Referring to table 3 in below link, it is up to 9216

http://www.cisco.com/en/US/prod/collateral/switches/ps5718/ps708/product_data_sheet0900aecd8017376e.html

Reza

[kyukim]

Hi,
In more detail, you can set mtu range 1500-9216 on Router port, 9216-9216 on swtich port and 64-9216 on SVI port on any 67XX sw module.

KK