[cisco-nas] ATM/L2TP/PPP MTU question

[Tassos Chatzithomaoglou]

Here is the network diagram:

           DSL         ATM              ATM         ATM       ETH
ADSL CPE ----- DSLAM ----- ATM SWITCH ----- BBRAS ----- LNS ----- INTERNET
     |-------------- PPPoE/A------------------||----L2TP---|
     |----------------------- PPP -------------------------|

What is the recommended MTU setting for the ip/atm connection between BBRAS/LNS (default 
for ATM is 4470), if we have to :

1. Do not change anything on user's side
2. Do not load BBRAS/LNS with extra fragmentation/reassembly

Should i make it 1540 (1500 + 40 bytes of IP, UDP and L2TP headers) ?

-- 
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    Chatzithomaoglou Anastasios
Network Design & Operations Center
           FORTHnet S.A.
       <achatz at forthnet.gr>
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