IBM Support

Checking if Large Send Offload is enabled

Troubleshooting


Problem

How to determine the Large Send Offload (LSO) status

Resolving The Problem

This information is displayed in NETSTAT native macro on 7.1 and later:



Command . . . . : NETSTAT

Options . . . . . -PIF


Running macro: NETSTAT                          -PIF                                                            
           VLAN                    I  Act       I  Act       S        Confg Actl  Intf  P                      
Line       ID    Type     Status   P Ifcs  MTU  P Ifcs  MTU  A Status  MTU   MTU  Index P                      
---------- ----- -------- -------- 4 ---- ----- 6 ---- ----- C ------ ----- ----- ----- PoE                    
NETWORK       0  Eth V2   Active   |   11  1500 |    0  1500 | N/A        0     0     2    IP,T4,LSO4,          
VLAN25        0  Eth V2   Active   |    3  9000 |    0  9000 | N/A        0     0     3    T4,T6,              
VIRTETH       0  Eth V2   Active   |    2  1500 |    0  1500 | N/A        0     0     4    T4,T6,              
TEST          0  *NONE    Inactive |    0     0 |    0     0 | N/A        0     0     5                        
*LOOPBACK     0  *NONE    Active   |    1   576 |    0 16384 | N/A        0     0     1    IP,T4,U4,T6,U6,      
TEST2         0  *NONE    Inactive |    0     0 |    0     0 | N/A        0     0     6                        
VLAN71        0  Eth V2   Active   |    4  1500 |    0  1500 | N/A        0     0     7    T4,T6,              
VLAN81        0  *NONE    Inactive |    0     0 |    0     0 | N/A        0     0     8                        
*VIRTUALIP    0  *NONE    Active   |    2   576 |    0 16384 | N/A        0     0     9                        
TESTVIPA1     0  *NONE    Inactive |    0     0 |    0     0 | N/A        0     0    10                        
TESTVIPA2     0  *NONE    Inactive |    0     0 |    0     0 | N/A        0     0    11                        
L224E9757F    0  PPP      Inactive |    0  1400 |    0     0 | N/A        0     0    12                        
****** END OF DUMP ******  



The "flags" at the end of each line indicate whether CKO (Checksum offload) or LSO (large send offload) are supported.
LSO4 means LSO is supported for TCP on IPv4.

(The IP, Tn, Un flags are for CKO support)


For 6.1 and other releases, LSO is enabled if packet length for CMNTRC is > 1500.


Note:
LSO for Virtual Ethernet was added to IBM i 7.1 with Tech Refresh 11 and IBM i 7.2 with Tech Refresh 3
 
An IBM Server with POWER8 technology and Firmware 840, or newer, is also required."

===========================================================

Please see the following document for information regarding enabling or disabling Large Send Offload (LSO) on the IBM i: N1022262

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Document Information

Modified date:
10 January 2020

UID

nas8N1021278