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Correct MTU settings for 3Com wireless router

paulus2007
Dabbler
Posts: 18
Registered: 30-07-2007

Correct MTU settings for 3Com wireless router

I have been struggling with poor speed. In the space of an hour my speedtests on this router (3CRWE754G72-A) the speed tests have ranged from < 200K to around 600K. I only have one computer currently running on the network.

Using a very basic Alcatel based modem/router (slagged off in the press and forums) on one occasion I managed 930K which is pretty reasonable for a 1Mb connection - about the same speed that I got from the BT speedtest.

The MTU is currently set at 1472 - which should be correct - but what should it be for this modem?

If it is a problem with the modem I'll scap it and try another - but I need a reliable wireless modem router to handle up to 6 wired computers and a couple of wireless connections.
7 REPLIES
comsiteuser
Newbie
Posts: 6
Registered: 30-07-2007

3Com MTU

I have had the best result to date with an MTU of 1492.
My current status is showing:

Stream Type Interleaved Channel Data Rate Fast Channel Data Rate
Up Stream 448 (Kbps.) 0 (Kbps.)
Down Stream 7616 (Kbps.) 0 (Kbps.)

Operation Data Upstream Downstream
Noise Margin 24 dB 9.5 dB
Output Power 12 dBm 18 dBm
Attenuation 8 dB 17 dB

In spite of this I am still only getting a downstream speed of at best 3150 Mbps. Any tips on improving this would be most welcome!
N/A

Correct MTU settings for 3Com wireless router

I am syncing at about 4mb so took Kitz's advice here and it works OK for me...Linky
...and I am using the same 3Com router as you

Edit - no I'm not, I am using the ...100A router but the same thing applies. It still won't help if the slowdown is contention at your exchange as I'm sure you know.
paulus2007
Dabbler
Posts: 18
Registered: 30-07-2007

Correct MTU settings for 3Com wireless router

OK, I have just switched to my ADSL-MR4A router/modem that I keep as a spare - and have set the MTU to 1500 and ADSLguide now reports a speed in excess of 930K - which isn't bad for 1Mb connection.

I'll operate without wireless for a bit and see if the results are consistent.
paulus2007
Dabbler
Posts: 18
Registered: 30-07-2007

Correct MTU settings for 3Com wireless router

Obviously it's the 3Com that is at fault - I have been achieving 930+K for the last 13 hours. My current MTU is set at 1500 and the speed and resilience has been brilliant.

Definitely time to get a new wireless ADSL/Router - looks as though the Speedtouch 585i is going to be the best around at the moment - what say you?
Alecto
Grafter
Posts: 2,886
Registered: 30-07-2007

Correct MTU settings for 3Com wireless router

Why do you need a wireless router anyway? Must be that a lot of people with them would be just as well served by a wired one.

Is there scientific evidence that changing the MTU really makes any difference? Speed test have such random results based on so many factors that it must be difficult to attribute an increase in speed to any particular cause.

I've just had a look and my MTU is 1458 - I've never changed it from the days of 512kb. Dr TCP says to change it to 1500, but I think I'll just leave it alone.
paulus2007
Dabbler
Posts: 18
Registered: 30-07-2007

Correct MTU settings for 3Com wireless router

I have 5 desktop pcs/servers in my office at home + another desktop pc in another part of the house - and general consensus is no wires please! So my local network is ok - but the rest of the house is wireless.

My router said to use the default of 1500 - and I got the best speed there. The 3com was up and down like a yoyo - I'm going to ditch it the the (vain) hope that I will get some better reliability.

Will let you know how it pans out...
comsiteuser
Newbie
Posts: 6
Registered: 30-07-2007

Correct MTU settings for 3Com wireless router

Hve you upgraded the firmware in your 3Com? I don't know whether it would help.