[c-nsp] ip tcp adjust-mss

[Blake Dunlap]

Yes. Don't do that.


On Mon, Nov 4, 2013 at 6:59 PM, Methsri Wickramarathna <mmethw2003 at gmail.com
> wrote:

> Thanks Tony , John and Juergan...
>
> This has been issue for many sites mainly towards yahoo.com. Can any one
> explain why this is happening for particular IPs in a subnet ???
> We are using access list inbound & Outbound to prevent ICMPs cumming inside
> to our network, will it be creating this problem ????
>
>
> On Tue, Nov 5, 2013 at 3:23 AM, <cnsp at marenda.net> wrote:
>
> > Hi, this looks like a CPE-device
> > With static IP-adresses and routing.
> >
> > You may really want to set "ip tcp adjust-mss 1280"
> > on _both_ your WAN and your (probably natted) LAN (L3) Interfaces.
> > (_both_ sides, yes !)
> >
> > This will help you in most cases with
> > MTU restrictions on
> > - your link
> > - home-"web"servers behind Broadband links
> > etc.
> >
> > Yes, the value is not optimized but very computerish ( 2**10 + 2**8 ),
> > but it is good for
> > - pppoe (1500-8=1492)
> > - l2tp forwarded dial-in sessions (l2tp overhead+pppoe leads to 1456)
> > - even with an additional vlan tag ( so MTU will be 1452 found in most
> > literature)
> > - some other tunneled environments
> >
> > Iff you are an ISP,
> > you will configure this _only_ on the virtual-template interfaces
> > on your LNSes for broadband-termination .
> >
> > Keep it out of your core,
> > You will not want to modify your valued customer's ip packets
> > in your core network; here you want to use a MTU greater than 1500
> > while on your BGP up/downstreams will stay at Ethernet-default 1500 .
> >
> > Sorry, very conservative, but will avoid may problems.
> >
> > Just my 0.01 $ on this
> >
> > Juergen.
> >
> > > -----Ursprüngliche Nachricht-----
> > > Von: cisco-nsp [mailto:cisco-nsp-bounces at puck.nether.net] Im Auftrag
> > > von Methsri Wickramarathna
> > > Gesendet: lundi 4 novembre 2013 17:55
> > > An: Pete Lumbis
> > > Cc: cisco-nsp at puck.nether.net
> > > Betreff: Re: [c-nsp] ip tcp adjust-mss
> > >
> > > Thanks Pete,
> > >
> > > If not a problem can any one look in to following mturoute taken ??? :)
> > >
> > > E:\>mturoute -t www.ubnt.com
> > > mturoute to www.ubnt.com, 30 hops max, variable sized packets
> > > * ICMP Fragmentation is not permitted. *
> > > * Speed optimization is enabled. *
> > > * Maximum payload is 10000 bytes. *
> > >  1  +-  host: 116.12.78.1  max: 1500 bytes
> > [...]
> >
> >
>
>
> --
> --
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> ~~( ŊëŌ )~~
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