[AusNOG] Telstra ADSL MTU

[Nathan Brookfield]

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> on behalf of Adam Baxter <adam1984 at gmail.com>
Sent: Tuesday, 2 August 2016 3:35 PM
To: 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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