[c-nsp] Fwd: IPV6 Path MTU DIscovery Test

Oliver Boehmer (oboehmer) oboehmer at cisco.com
Wed Aug 1 02:18:31 EDT 2012


Well, you need to create TCP connections to see the effect of PMTUD.. you could build an iBGP session across the test network, and play around with the minimum link MTU along the path. The MSS (shown in show bgp neighbor ..) should adapt as you change it..  

	oli

> -----Original Message-----
> From: cisco-nsp-bounces at puck.nether.net [mailto:cisco-nsp-
> bounces at puck.nether.net] On Behalf Of Xu Hu
> Sent: 01 August 2012 02:33
> To: cisco-nsp at puck.nether.net
> Subject: [c-nsp] Fwd: IPV6 Path MTU DIscovery Test
> 
> Anybody have any good idea?
> 
> Thanks advance for any inputs,
> Xu Hu
> 
> Begin forwarded message:
> 
> > From: TJ <trejrco at gmail.com>
> > Date: 1 August, 2012 5:23:46 GMT+08:00
> > To: Xu Hu <jstuxuhu0816 at gmail.com>
> > Subject: Re: [c-nsp] IPV6 Path MTU DIscovery Test
> > Reply-To: trejrco at gmail.com
> >
> > In order to test it, take one of the links along the path and change the
> (IPv6) MTU to something smaller - say 1300B.  Then send large packets, with
> WireShark running.  And no, you cannot disable PMTUD in IPv6.
> >
> > HTH!
> > /TJ
> >
> >
> > On Tue, Jul 31, 2012 at 6:43 AM, Xu Hu <jstuxuhu0816 at gmail.com> wrote:
> > Hi Experts,
> >
> > I have some queries about the PMTU for IPv6.
> > 1. From my understanding, path MTU discovery in IPv6 allows a host to
> > dynamically discover and adjust to differences in the MTU size of every
> > link along a given data path, So the fragmentation is handled by the
> > source, if i want to test this feature in the IPv6 network, anyone have
> any
> > good ideas?
> > For example, as below topology, if i want to test the Path MTU discovery,
> > how to test, i can ping from CE-1  to CE--2 with a specific IPv6 packet
> > size.
> > CE-1------PE-1------------PE-2--------CE-2
> >
> > 2. If i need to configure the Path MTU discovery, just one command
> > mentioned in Cisco.com, which is "ipv6 flowset" under configuration mode.
> > So if i want to disable that in test scenario, just using the "no ipv6
> > flowset" is okay? Cisco don't mentioned that.
> > By default, it is enable for ip routers or not?
> >
> > Thanks for any inputs.
> >
> > Best Regards,
> > Hu Xu
> > _______________________________________________
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> >
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