In reply to a post by E7er:

My Bright Box has mysteriously changed, it will now no longer save the MTU 1500 only up to 1492.

Peculiiar! Perhaps they remotely "upgraded" firmware. Have you checked the firmware versions have not changed?

In reply to a post by E7er:

So it looks the router MTU 1492 is required for Orange network.

No. it's your BrightBox restricting it as stated and confirmed earlier.

You can do the same tests with a Netgear set to MTU = 1500 and pings up to 1472 will succeed on the Orange WBC network

EDIT: Are you sure you haven't set MTU = 1492 in the PC?

Edited by XRaySpeX (Mon 24-Sep-12 19:48:28)

That is very interesting! I was previously puzzled by eckiedoo not getting the usual ping msg. when fragmentation needed as here:

In reply to a post by E7er:

MTU set at 1492

Pinging www.bbc.net.uk [212.58.244.68] with 1465 bytes of data:

Reply from 192.168.13.251: Packet needs to be fragmented but DF set.
Packet needs to be fragmented but DF set.
Packet needs to be fragmented but DF set.
Packet needs to be fragmented but DF set.

vs.

MTU set at 1500

Pinging www.bbc.net.uk [212.58.246.93] with 1465 bytes of data:

Request timed out.
Request timed out.
Request timed out.
Request timed out.

It looks as though when the BrightBox has an MTU above its allowable range it does not respond to the fragmentable ping with the usual "fragmentation needed" Reply but instead ignores the ping completely .

Morning again

Thanks for your clear instructions re Copying etc.

For completeness, I tried pinging at the low end-

100

29
28
27

1
0
-1

Results are-


Microsoft Windows [Version 6.0.6002]
Copyright (c) 2006 Microsoft Corporation. All rights reserved.

C:\Users\Alex>ping -f -l 100 www.bbc.co.uk

Pinging www.bbc.net.uk [212.58.246.90] with 100 bytes of data:
Reply from 212.58.246.90: bytes=100 time=24ms TTL=54
Reply from 212.58.246.90: bytes=100 time=24ms TTL=54
Reply from 212.58.246.90: bytes=100 time=24ms TTL=54
Reply from 212.58.246.90: bytes=100 time=24ms TTL=54

Ping statistics for 212.58.246.90:
Packets: Sent = 4, Received = 4, Lost = 0 (0% loss),
Approximate round trip times in milli-seconds:
Minimum = 24ms, Maximum = 24ms, Average = 24ms

C:\Users\Alex>ping -f -l 29 www.bbc.co.uk

Pinging www.bbc.net.uk [212.58.246.90] with 29 bytes of data:
Reply from 212.58.246.90: bytes=29 time=24ms TTL=54
Reply from 212.58.246.90: bytes=29 time=24ms TTL=54
Reply from 212.58.246.90: bytes=29 time=24ms TTL=54
Reply from 212.58.246.90: bytes=29 time=24ms TTL=54

Ping statistics for 212.58.246.90:
Packets: Sent = 4, Received = 4, Lost = 0 (0% loss),
Approximate round trip times in milli-seconds:
Minimum = 24ms, Maximum = 24ms, Average = 24ms

C:\Users\Alex>ping -f -l 28 www.bbc.co.uk

Pinging www.bbc.net.uk [212.58.246.90] with 28 bytes of data:
Reply from 212.58.246.90: bytes=28 time=25ms TTL=54
Reply from 212.58.246.90: bytes=28 time=24ms TTL=54
Reply from 212.58.246.90: bytes=28 time=23ms TTL=54
Reply from 212.58.246.90: bytes=28 time=24ms TTL=54

Ping statistics for 212.58.246.90:
Packets: Sent = 4, Received = 4, Lost = 0 (0% loss),
Approximate round trip times in milli-seconds:
Minimum = 23ms, Maximum = 25ms, Average = 24ms

C:\Users\Alex>ping -f -l 27 www.bbc.co.uk

Pinging www.bbc.net.uk [212.58.246.90] with 27 bytes of data:
Reply from 212.58.246.90: bytes=27 time=24ms TTL=54
Reply from 212.58.246.90: bytes=27 time=23ms TTL=54
Reply from 212.58.246.90: bytes=27 time=24ms TTL=54
Reply from 212.58.246.90: bytes=27 time=24ms TTL=54

Ping statistics for 212.58.246.90:
Packets: Sent = 4, Received = 4, Lost = 0 (0% loss),
Approximate round trip times in milli-seconds:
Minimum = 23ms, Maximum = 24ms, Average = 23ms

C:\Users\Alex>ping -f -l 10 www.bbc.co.uk

Pinging www.bbc.net.uk [212.58.246.90] with 10 bytes of data:
Reply from 212.58.246.90: bytes=10 time=24ms TTL=54
Reply from 212.58.246.90: bytes=10 time=25ms TTL=54
Reply from 212.58.246.90: bytes=10 time=23ms TTL=54
Reply from 212.58.246.90: bytes=10 time=24ms TTL=54

Ping statistics for 212.58.246.90:
Packets: Sent = 4, Received = 4, Lost = 0 (0% loss),
Approximate round trip times in milli-seconds:
Minimum = 23ms, Maximum = 25ms, Average = 24ms

C:\Users\Alex>ping -f -l 1 www.bbc.co.uk

Pinging www.bbc.net.uk [212.58.246.90] with 1 bytes of data:
Reply from 212.58.246.90: bytes=1 time=24ms TTL=54
Reply from 212.58.246.90: bytes=1 time=23ms TTL=54
Reply from 212.58.246.90: bytes=1 time=23ms TTL=54
Reply from 212.58.246.90: bytes=1 time=23ms TTL=54

Ping statistics for 212.58.246.90:
Packets: Sent = 4, Received = 4, Lost = 0 (0% loss),
Approximate round trip times in milli-seconds:
Minimum = 23ms, Maximum = 24ms, Average = 23ms

C:\Users\Alex>ping -f -l 0 www.bbc.co.uk

Pinging www.bbc.net.uk [212.58.246.90] with 0 bytes of data:
Reply from 212.58.246.90: bytes=0 time=23ms TTL=54
Reply from 212.58.246.90: bytes=0 time=23ms TTL=54
Reply from 212.58.246.90: bytes=0 time=23ms TTL=54
Reply from 212.58.246.90: bytes=0 time=23ms TTL=54

Ping statistics for 212.58.246.90:
Packets: Sent = 4, Received = 4, Lost = 0 (0% loss),
Approximate round trip times in milli-seconds:
Minimum = 23ms, Maximum = 23ms, Average = 23ms

C:\Users\Alex>ping -f -l -1 www.bbc.co.uk
Bad value for option -l, valid range is from 0 to 65500.

C:\Users\Alex>

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

Re E7er managing to restore the 1500, I wonder if the SAVE operation covers the complete firmware, rather than simply the Parameters such as 1500?

That is reverting to the SAVEd version also restores the full older firmware; rather than simply the Parameter Values.