[c-nsp] ip tcp adjust-mss

[cnsp at marenda.net]

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
[...]