[AusNOG] TPG EFM - low MTU

[McDonald Richards]

Pretty sure the PPP header is still there at that point but the 1492
client wan normally fragments packets to prevent it being an issue so 1540
would still be your maximum required size to the LAC.

Macca


On 23/06/14 3:35 PM, "Andrew Jones" <aj at jonesy.com.au> wrote:

>I don't think you need to add another 8 on top of the 40 for PPPoE,
>because that part of the frame gets stripped before it goes into the
>l2tp tunnel, unless I'm mistaken...
>
>On 23.06.2014 15:26, McDonald Richards wrote:
>> You need to be able to hit a LAC at 1540 bytes from your LNS if you
>> don't want to be fragmenting clients. Add another 8 bytes for PPPOE…
>>
>> Macca
>>
>>  From: Bruce Forster <bruce at tubes.net.au>
>>  Date: Monday, 23 June 2014 3:20 PM
>>  To: "ausnog at ausnog.net" <ausnog at ausnog.net>
>>  Subject: [AusNOG] TPG EFM - low MTU
>>
>> Hi Noggers,
>>
>>  I have a strange issue seems to be isolated to VIC LAC's
>>
>>  Some session are coming up at MTU 1476.
>>
>>  I did managed to clear a l2tp tun and the session came back via
>> another LAC at 1500.
>>
>>  These are the ones i have had problems with: TPGVICLAC-6e
>> / TPGVICLAC-5e
>>
>>  To get around it iv set mtu on the dialer to match and used a
>> mss-adjust...
>>
>> I can ping to the LAC's IP at 1500 with no issue.
>>
>>  --
>>  Regards,
>>
>>  Bruce
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>
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