[AusNOG] Telstra ADSL MTU

[Burt Mascareigne]

Hi,

We have client’s that have this constant problem.  I tweak the MTU to 1400 sometimes… and then everyone works magically.  1492 causes havoc.  I once set It to 1500,  and it worked.. Don’t ask.. I took it to 1450 (I think) didn’t dare leave it on 1500 for ADSL.

We’ve moved away from Cisco to SOPHOS, and there’s no mss-adjust.  We use a TD-8817 in bridge mode.  We have tried other bridge modems, no difference.

What’s people recommendation for us non – cisco souls? Is it the bridge causing this?  Don’t see how, it’s dialler level.  Unless I’m being blond for something obvious.


Regards,


Burt Mascareigne
Mobile 0414 450 962   Office (02) 9965 5422
Address Level 19, 1 O’Connell Street, Sydney NSW 2000
Web http://www.stormnetwork.com.au<http://www.stormnetwork.com.au/>

From: AusNOG [mailto:ausnog-bounces at lists.ausnog.net] On Behalf Of Shane Short
Sent: Tuesday, 2 August 2016 8:03 PM
To: Adam Baxter <adam1984 at gmail.com<mailto:adam1984 at gmail.com>>
Cc: AusNOG at lists.ausnog.net<mailto:AusNOG at lists.ausnog.net>
Subject: Re: [AusNOG] Telstra ADSL MTU

Is there a particular reason you're running 1452 on the dialer? Was it a troubleshooting step, or?

Adam Baxter wrote:
Thank you!

On 2 August 2016 at 15:39, Nathan Brookfield <Nathan.Brookfield at simtronic.com.au<mailto:Nathan.Brookfield at simtronic.com.au>> wrote:

Hi Adam,



As a rule your mss-adjust should be 40 bytes lower than your actual MTU.  In theory you should have 1492 on the dialer and and an mss-adjust of 1452 on the LAN interface.



If you're going to keep 1452 on the Dialer as the MTU you should adjust the mss appropriately.  See if that helps at all.



Kindest Regards,

Nathan Brookfield (VK2NAB)



Chief Executive Officer

Simtronic Technologies Pty Ltd



Local: (02) 4749 4949 | Fax: (02) 4749 4950 | Direct: (02) 4749 4951

Web: http://www.simtronic.com.au<http://www.simtronic.com.au/> | E-mail: nathan.brookfield at simtronic.com.au<mailto:nathan.brookfield at simtronic.com.au>



________________________________
From: AusNOG <ausnog-bounces at lists.ausnog.net<mailto:ausnog-bounces at lists.ausnog.net>> on behalf of Adam Baxter <adam1984 at gmail.com<mailto:adam1984 at gmail.com>>
Sent: Tuesday, 2 August 2016 3:35 PM
To: AusNOG at lists.ausnog.net<mailto:AusNOG at lists.ausnog.net>
Subject: [AusNOG] Telstra ADSL MTU

Hi All,
I have had 2 Customers in the last few weeks that have had MTU problems. This is my Dialer interface.

interface Dialer0
 ip address negotiated
 no ip redirects
 no ip unreachables
 no ip proxy-arp
 ip mtu 1452
 ip nat outside
 ip virtual-reassembly
 encapsulation ppp
 load-interval 30
 dialer pool 1
 dialer-group 1
 no cdp enable
 ppp authentication chap callin
 ppp chap hostname xxxx at direct.telstra.net<mailto:xxxx at direct.telstra.net>
 ppp chap password 7 xxxxx
end
 I have never had any problems accessing websites until the last few weeks. Does anyone know what might have changed at the Telstra end? I had to set  "ip tcp adjust-mss 1452" on the Dialer interface to make it work. Never had to in the past with a number of other connections. Perhaps I should have all along?
Regards,
Adam.



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