Jumbo frame on 6500 switch

[VanessaW]

question about Giants packages on 10G interfaces that enabled Jumbo frame.

configured 10G port mtu 9216.

when show interface...shows giants as below:

     Received 163650 broadcasts (0 multicasts)

     0 runts, 745153379 giants, 0 throttles

does the "giants" mean mtu > 9216 and got dropped?

when show counters interface...shows as below:

~~~elimitnated...

All Port Counters

1.                          InPackets = 271909396041

2.                           InOctets = 1502779448781201

3.                        InUcastPkts = 271908838413

4.                        InMcastPkts = 0

5.                        InBcastPkts = 557648

6.                         OutPackets = 151646276794

7.                          OutOctets = 11937789067667

8.                       OutUcastPkts = 151543625135

9.                       OutMcastPkts = 77708276

10.                       OutBcastPkts = 24943383

11.                           AlignErr = 0

12.                             FCSErr = 0

13.                            XmitErr = 0

14.                             RcvErr = 0

15.                          UnderSize = 0

16.                          SingleCol = 0

17.                           MultiCol = 0

18.                            LateCol = 0

19.                       ExcessiveCol = 0

20.                       CarrierSense = 0

21.                              Runts = 0

22.                             Giants = 150758301785

23.                         InDiscards = 0

24.                        OutDiscards = 0

25.                           InErrors = 0

26.                          OutErrors = 0

27.                    InUnknownProtos = 0

28.                              txCRC = 0

29.                      TrunkFramesTx = 0

30.                      TrunkFramesRx = 0

31.                         WrongEncap = 0

32.     Broadcast_suppression_discards = 0

33.     Multicast_suppression_discards = 0

34.       Unicast_suppression_discards = 0

35.                 rxTxHCPkts64Octets = 124273884447

36.            rxTxHCPkts65to127Octets = 27814385978

37.           rxTxHCPkts128to255Octets = 3499741663

38.           rxTxHCPkts256to511Octets = 198634966

39.          rxTxHCpkts512to1023Octets = 1876993952

40.         rxTxHCpkts1024to1518Octets = 115096007733

41.                         DropEvents = 0

42.                     CRCAlignErrors = 0

43.                     UndersizedPkts = 0

44.                      OversizedPkts = 150758430153

~~~eliminated

does the above "giants" and"OversizedPkts" mean mtu > 9216?  got dropped?

Thank you!

[Somasundaram Jayaraman · Accepted solution]

Hi,

Jumbo frames are not defined as part of the IEEE Ethernet standard and are vendor-dependent. They can be defined as any frame bigger than the standard ethernet frame of 1518 bytes (which includes the L2 header and Cyclic Redundancy Check (CRC)). Jumbos have larger frame sizes, typically > 9000 bytes.

Giant frames are defined as any frame over the maximum size of an ethernet

frame (larger than 1518 bytes) that has a bad FCS.

Baby Giant frames are just slightly larger than the maximum size of an

ethernet frame. Typically this means frames up to 1600 bytes in size

if your 6708 is configured as a trunk port likely you see the giants due to 

CSCef87392 (for 6704) and CSCtb68386 (for 6708).

They are both accounting related defects, hence just cosmetic.

Hope this helps

Cheers

Somu

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[Richard Michael · Accepted solution]

Hello,

Any packet which is greater than MTU packet but less than the configured MTU will be counted as an oversized packet and will be shown as giant packets increasing. The interface will just report them as giants but will not drop then since the MTU on the interface is greater than the received packet size.

The below link might interest you

http://www.cisco.com/en/US/docs/ios/11_3/configfun/command/reference/frshowse.html

Giants :

Number of packets that are discarded because they exceed the medium's maximum packet size. For example, any Ethernet packet that is greater than 1,518 bytes is considered a giant.

Thanks,

Ricky Micky

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[VanessaW]

thank you all for the clarification!