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This is the support site for Andrews & Arnold Ltd, a UK Internet provider. Information on these pages is generally for our customers but may be useful to others, enjoy!

Category:Incoming L2TP: Difference between revisions

Category:Incoming L2TP (view source)

Revision as of 10:32, 4 April 2025

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__NOTOC__<indicator name="L2TP">[[File:Menu-L2TP.svg|link=:Category:L2TP|30px|Back up to the L2TP Category]]</indicator>
= L2TPWhy fromuse Customersout toL2TP AAISPservice? =
 
There are two reasons to use L2TP to connect in to AAISP:
# Connect in to AAISP over a third-party internet connection.
#* This gives you your an AAISP IPv4 address and an IPv6 block. This will then give you unfiltered internet access with public IP addresses etc.
#* Speed is capped at 200Mb/s (3Mb/s for the low-cost Light service).
#* There are more reasons for doing this and further information and ordering on [https://www.aa.net.uk/broadband/l2tp-service/ A&A L2TP service].
 
 
=== MTU ===
* see: [[L2TP MTU]]
 
The payload
 
{| class="wikitable"
|+ Rough guide for MTU for L2TP
|-
! ISP's Type !! ISP MTU !! L2TP MYU
|-
| Most broadband providers || 1492 || 1454
|-
| Broadband using Ethernet or baby jumbo frames RFC4638 || 1500 || 1462
|-
| Mobile or other || lower than 1492 || Lower than 1454
|}
 
* To find out the MTU of your underlying internet connection, see out [[MTU|MTU Page]]
* Generally, the L2TP MTU would be 38 bytes less than the MTU you have on the underlying internet connection.
* In theory fragments will work to allow 1500 MTU on our service, but fragments are inefficient, and if everyone sends fragmented packets that could degrade the service.
 
'''Technical Breakdown:'''
Here's a breakdown of the headers and the bytes used. This is using a standard PPP broadband connection where traffic through the ISP is 1492
 
Ethernet 1500 1500
802.11Q* - 4* 1500 (* Treated as part of the ethernet header and doesn't affect the MTU)
PPPoE - 6 1494
PPP - 2 1492 <-- the MTU of the underlying internet connection
IPv4 - 20 1472
UDP - 8 1464
L2TP - 6 1458
(HDLC) - 2 1456
PPP - 2 1454 <-- the MTU of the L2TP service
 
=== Port forwarding on some 'Mobile Broadband' routers ===
 
= Notes on setting up L2TP IN to AAISP: =
{{AAMenu|img=menu-packet.svg|title=MTU|link=L2TP_MTU|text=Learn about MTU and L2TP}}
{{AAMenu|img=Menu-FireBrick.svg|link=L2TP_Client:_FireBrick|title=L2TP from FireBrick|text=Creating a L2TP connection from a FireBrick to AAISP}}
{{AAMenu|img=Menu-Apple.svg|link=L2TP_Client:_OSX|title=L2TP from OSX|text=Creating a L2TP connection from Apple OSX to AAISP}}
AA-Andrew
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