Q. How can I test if two machines are using jumbo frames?

A. An easy way to check if you're sending 9kB packets instead of the 1.5kB standard is to use the ping command. Use a data size of 8kB bytes along with the no-fragment switch.

ping  -f -l 8000

As can be seen in my example below, I can successfully use jumbo frames to talk to savdalvs02, but not to savdalwks01. If I reduce the packet size to 800B, it works just fine for non-jumbo frame hosts.

If I use the command

ping savdalvs02 -f -l 8000

I'll see

Pinging savdalvs02.savilltech.net \[192.168.1.31\] with 8000 bytes of data:
Reply from 192.168.1.31: bytes=8000 time<1ms TTL=128
Reply from 192.168.1.31: bytes=8000 time<1ms TTL=128
Reply from 192.168.1.31: bytes=8000 time<1ms TTL=128
Reply from 192.168.1.31: bytes=8000 time<1ms TTL=128

Ping statistics for 192.168.1.31:
Packets: Sent = 4, Received = 4, Lost = 0 (0% loss),
Approximate round trip times in milli-seconds:
Minimum = 0ms, Maximum = 0ms, Average = 0ms

But if I enter

ping savdaldc10 -f -l 8000

I'll see

Pinging savdaldc10.savilltech.net \[192.168.1.10\] with 8000 bytes of data:
Request timed out.
Request timed out.
Request timed out.
Request timed out.

Ping statistics for 192.168.1.10:
Packets: Sent = 4, Received = 0, Lost = 4 (100% loss),

Related Reading:

• Q. How do I enable jumbo frames?
• Q. Should I disable NetBIOS over TCP/IP on my Windows Server 2008 R2 Cluster Shared Volume (CSV) cluster networks?
• New Features in Windows Server 2008 R2
• What You Need to Know About Hyper-V 2.0

Check out hundreds more useful Q&As like this in John Savill's FAQ for Windows. Also, watch instructional videos made by John at ITTV.net.