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No.340 I can't write configurations to ezTCP devices via ezManager!!! 05-07-2017
Category : can not


This happen when using ezManager to wire the environment parameter to ezTCP devices in some computers

Maximum transmission unit (MTU)


In computer network, a MTU is the largest size(unit: byte) of data for each protocol.
For example, the MTU of Ethernet is 1,500. And the data part of Ethernet is IP datagram.
It means if IP datagram size is over 1,500 bytes, it has to be fragmented.

MTU for some ezTCP devices


An ezManager search(response) and write(request/response) packet(UDP datagram) size depends on the products.
Note that an IP datagram size of an ezManger search(request) is fixed to 60(IP header 20 + UDP header 8 + UDP data 32) bytes.
Please refer to the table below for the datagram size of ezTCPs.

items UDP datagrams IP datagrams
CIE-H10/M10 1,440 1,468
CSE-M32/H20/H21 724 752
CSE-M73/H25/M53/H53/H55 592 620
CIE-H12 824 852
CIE-H14 1,196 1,224
CSE-M53N/H53N/H55N 732 760
CSC-H64 1420 1448



MTU issues


The MTU size for IP datagram of most network system is 1,500 as default.
However, for some reason, this value can be different.
When the size of an ezManager packet exceed the MTU of the system,
it should be fragmented as mentioned above.
But most ezTCP doesn't support IP fragmentation.
It means the response(both search and write) packet from ezTCP is NOT fragmented.
And also ezTCP can't receive the fragmented write(request) packet from ezManager.

That's why user can find an ezTCP with ezManager but not write configurations.

How to change the MTU size on Windows


1. Check the MTU size
Run command prompt as administrator

command - netsh interface ipv4 show interfaces


2. Change the MTU size
command - netsh interface ipv4 set subinterface "index number" mtu="size for changing"





- See also

- Related Products
[ I/O ] CIE-H10, CIE-M10
CSC-H64