[ LUGOS ] MTU?

[Tomaz Borstnar]

At 07:50 PM 3/21/99 , Jernej Horvat wrote the following message:
>> Heh... zdaj ko sem si porihtal ppp me zanima lynx.
>> Ob "connectu" napise MTU= 1500 (nekaj takega)
>> Kolikor jaz vem je optimalna vrednost nekje 576
>Kernel ima tudi MTU Auto discovery, ki pa ne dela vedno pravilno.
Verjetno dela pravilno - tezave tipicno nastopijo drugje:

>(nekateri routerji ne spustijo ICMP pakete skozi AFAIK)
Tezave so lahko, ce se v omrezju uporabljajo privatne adrese za omrezno
opremo ter nepravilno blokiranje ICMP. Citat iz freebsd-isp liste (Josh
Franta <josh na frantastic.com>):

This RFC describes the "best" practices for using reserved addresses.  A
less strict way to interprut rfc1918 might be to say that any host
(interface) that uses rfc1918 address space shouldn't *expect*
connectivity to the public Internet (short of some sort of gateway).  

NANOG had a related discussion several weeks ago.  Basically what it came
down to was that using rfc1918 address space on p2p links *may* break PMTU
discovery.  It would only break PMTU discovery when one of the involved
parties (including trasit ASs) filters the RFC1918 address space.  This
type of filtering happens to be recommened in rfc1918 :).  So it's
probably not recommened since it could potentially cause you problems.

For more information, check out: http://users.worldgate.com/~marcs/mtu/

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Tomaz Borstnar <tomaz.borstnar na over.net>
"Love is the answer to the final question you ask" - Unknown