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Standard User SimpleSimon1
(newbie) Mon 24-Feb-14 17:34:14
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FYI: Recommended MTU on Coms Network


[link to this post]
 
In case anyone was wondering (I recall one post asking this), I raised a ticket this morning asking what the recommended MTU was on the Coms network. Got a reply within 3 hours (IMHO pretty good for an RFI; they normally go to the bottom of the pile!) stating 1492. Ping fragmentation tests seems to confirm this value so have updated my router accordingly and everything seems to be nipping along quite nicely.
Standard User bobble_bob
(fountain of knowledge) Mon 24-Feb-14 18:11:12
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Re: FYI: Recommended MTU on Coms Network


[re: SimpleSimon1] [link to this post]
 
Mine is 1458, i thought 1492 was for PPPoE connections, where as we're on PPPoA
Standard User SimpleSimon1
(newbie) Mon 24-Feb-14 19:44:20
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Re: FYI: Recommended MTU on Coms Network


[re: bobble_bob] [link to this post]
 
Well, we're defo on PPPoA but if you do a ping fragmentation test, 1464 pings correctly and 1465 fragments. When you add the +28 for the headers, that makes 1492...which is what Coms Tech Support recommended


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Standard User XRaySpeX
(eat-sleep-adslguide) Mon 24-Feb-14 19:51:59
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Re: FYI: Recommended MTU on Coms Network


[re: bobble_bob] [link to this post]
 
Yes, 1492 is for PPPoE connections, it's 1500 0n BTw PPPoA connections.

1999: Freeserve 48K Dial-Up => 2005: Wanadoo 1 Meg BB => 2007: Orange 2 Meg BB => 2008: Orange 8 Meg LLU => 2010: Orange 16 Meg LLU => 2011: Orange 20 Meg WBC
Standard User bobble_bob
(fountain of knowledge) Mon 24-Feb-14 19:56:20
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Re: FYI: Recommended MTU on Coms Network


[re: XRaySpeX] [link to this post]
 
Ive always been on 1458 its what my router defaults too, what advantages (if any) would i get from changing it to 1500?
Standard User XRaySpeX
(eat-sleep-adslguide) Mon 24-Feb-14 19:56:21
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Re: FYI: Recommended MTU on Coms Network


[re: SimpleSimon1] [link to this post]
 
In reply to a post by SimpleSimon1:
1465 fragments.
Are you sure you've freed MTU to 1500 everywhere , in router and PC OS, before doing ping fragmentation test?

Who supplies Coms connection? If BTw, ping 1472 should not fragment.

1999: Freeserve 48K Dial-Up => 2005: Wanadoo 1 Meg BB => 2007: Orange 2 Meg BB => 2008: Orange 8 Meg LLU => 2010: Orange 16 Meg LLU => 2011: Orange 20 Meg WBC
Standard User XRaySpeX
(eat-sleep-adslguide) Mon 24-Feb-14 19:57:10
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Re: FYI: Recommended MTU on Coms Network


[re: bobble_bob] [link to this post]
 
Fewer fragmented packets?

1999: Freeserve 48K Dial-Up => 2005: Wanadoo 1 Meg BB => 2007: Orange 2 Meg BB => 2008: Orange 8 Meg LLU => 2010: Orange 16 Meg LLU => 2011: Orange 20 Meg WBC
Standard User SimpleSimon1
(newbie) Mon 24-Feb-14 20:55:01
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Re: FYI: Recommended MTU on Coms Network


[re: XRaySpeX] [link to this post]
 
Ah, fair point. I'm set to 1500 in the OS but 1496 in the Router BUT my router is a 1-year old TP-Link TD-W8960N Wireless N ADSL2+ jobbie and according to both screen legend and doco, only supports a max MTU setting of 1492!

I wonder if this is the rule rather than the exception as far as routers go and that's why they're suggesting a value of 1492 rather than 1500?
Standard User XRaySpeX
(eat-sleep-adslguide) Mon 24-Feb-14 22:30:09
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Re: FYI: Recommended MTU on Coms Network


[re: SimpleSimon1] [link to this post]
 
Fair point! If your router limits you then your hands are tied and you just pay by the odd 8 byte unnecessary fragmentation.

Duuno how general this is but my ISP's Orange/EE Brightbox was limited also to MTU <= 1492 until an update & our nagging got them to change it in late 2012 & now we're home free.

1999: Freeserve 48K Dial-Up => 2005: Wanadoo 1 Meg BB => 2007: Orange 2 Meg BB => 2008: Orange 8 Meg LLU => 2010: Orange 16 Meg LLU => 2011: Orange 20 Meg WBC
Standard User My_brain_hurts
(learned) Tue 25-Feb-14 04:06:12
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Re: FYI: Recommended MTU on Coms Network


[re: XRaySpeX] [link to this post]
 
This may help some -

http://www.tp-link.pt/article/?id=69

http://www.tp-link.com/en/article/?faqid=190

Is there anywhere on Coms site that states what settings we should use for our modems?

Edited by My_brain_hurts (Tue 25-Feb-14 05:17:19)

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