Hi Ragnar, What is the MTU as seen by the IPv6 hosts - 1480? Something less? Would it not be better if they could see 1500+?
Thanks - Fred [email protected] > -----Original Message----- > From: [email protected] > [mailto:ipv6-ops- > [email protected]] On Behalf Of Anfinsen, > Ragnar > Sent: Thursday, January 09, 2014 5:35 AM > To: IPv6 Ops list > Subject: RE: MTU handling in 6RD deployments > > Hi all. > > We have now changed and upgraded our BR to handle MTU in a sensible manner. > > We are not able to set the IPv4 MTU to more than 1500 due to limitations in > our Cisco Cat4500 > platform. So we have to reduce the MTU to 1480 somehow. > > Our other problem is that, by mistake, our RA MTU size is set to 1500, and > not 1480, as it should be. > This will be fixed in the next firmware we push out. > > Due to the problem with the MTU size, we had a lot of ICMPv6 PTB packets > being returned from the Cisco > 1K unit (BR). This again results to that the rate-limiting feature in the 1K > dropped a lot of the PTB > messages going back to the sender, hence making the IPv6 experience sluggish. > Typical problems was > that pictures and such had some timeout before they were loaded. > > To fix this issue, we first of all upgraded our 1K's to the latest IOS (Cisco > IOS XE Software, Version > 03.11.00.S) which has the MSS-Clamping feature. This feature was added by > Cisco in November. Then we > added the command "ipv6 tcp adjust-mss 1420" to the 6rd tunnel interface. > > With this command set, all ICMPv6 PTB packets has disappeared, and the whole > IPv6 experience has > become a whole lot better with snappy loading of pages and pictures. So for > TCP everything is good. As > soon as we have fixed our firmware, this problem should be gone all together. > > Thanks to Tore Anderson for point this out to us. > > Hopefully this is useful for someone. > > Best Regards > Ragnar Anfinsen > > Chief Architect CPE > IPv6/IPv4 Architect > Infrastructure > Technology > Altibox AS > > Phone: +47 51 90 80 00 > Phone direct: +47 51 90 82 35 > Mobile +47 93 48 82 35 > E-mail: [email protected] > Skype: ragnar_anfinsen > www.altibox.no > > > > CONFIDENTIAL > The content of this e-mail is intended solely for the use of the individual > or entity to whom it is > addressed. If you have received this communication in error, be aware that > forwarding it, copying it, > or in any way disclosing its content to any other person, is strictly > prohibited. If you have received > this communication in error, please notify the author by replying to this > e-mail immediately, deleting > this message and destruct all received documents. >
