[c-nsp] Bellsouth DSL / PPPoE config

[Brian Feeny]

On Mar 3, 2005, at 6:57 PM, Joe Maimon wrote:
>>
>
> GRE is 24 overhead. If you run at 1440 ip mtu you are well under PPPoE 
> mtu. If you mean tcp adjust on that, just take 40 off mtu.
>

I am doing GRE + IPSec.  I was using the guidelines at 
http://www.cisco.com/warp/public/105/pmtud_ipfrag.html and
just assumed, that if 1440 was good for GRE + IPSec, then 1432 should 
be good for GRE + IPSec + PPPoE.


> I have previously argued to cisco that the gre tunnel pmtud feature 
> will not work well with tcp adjust mss on a tunnel interface because 
> they would not keep in sync. Really the tcp adjust mss should simply 
> specify an offset to be applied to whatever the current ip mtu is (its 
> not as if the number specified is always the number used -- tcp 
> options change the calculation). IIRC there was a ddts filed.
>
> If you want ipsec on gre tunnel, you might wish to use the tunnel 
> protection ipsec profile  xxxx method rather than crypto map.
>> Brian
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