Gareth,
This is a better link.
http://www.cisco.com/warp/public/105/56.html
HTH,
Phil.
--- Gareth Hinton <[EMAIL PROTECTED]>
wrote: > Hi Steve,
>
> Is the MTU size of 1476 a limitation of the
> encryption, or merely because of
> the overheads added by the encryption knocking it
> down from 1500. Is it a
> possibility to increase the MTU size on the link?
>
> Gaz
>
> "Phil Barker" <[EMAIL PROTECTED]> wrote in
> message
>
[EMAIL PROTECTED]">news:[EMAIL PROTECTED]...
> > Steve,
> > Without CLI access your going to struggle.
> > Q : How far does the traceroute get, from the send
> > node ?
> >
> > try rfc 792 ICMP
> > http://www.landfield.com/rfcs/rfc792.html
> >
> > >> SNIP from RFC 792
> >
> > If a host reassembling a fragmented datagram
> > cannot complete the
> > reassembly due to missing fragments within
> its
> > time limit it
> > discards the datagram, and it may send a
> time
> > exceeded message.
> >
> > If fragment zero is not available then no
> time
> > exceeded need be
> > sent at all.
> >
> > Good luck,
> >
> > Phil.
> >
> >
> >
> > --- "Donohue, Steve" <[EMAIL PROTECTED]>
> wrote:
> > > Good Afternoon All,
> > >
> > > I am currently trying to resolve an issue where
> we
> > > are having trouble
> > > sending data across a tunnel running GRE
> encryption.
> > > With this encryption
> > > employed the MTU size allowed is decreased to
> 1476.
> > > When we attempt to send
> > > traffic (email, ftp, etc...) through the tunnel,
> we
> > > are finding that it does
> > > not work.
> > >
> > > My sniffer trace is showing that the frames
> being
> > > sent are setting the DF
> > > bit, which I would expect. I would then expect
> that
> > > if the router is unable
> > > to send the packet, it would drop it and return
> an
> > > ICMP message back to the
> > > source telling it to decrease the packet size
> and
> > > try it again. I am not
> > > seeing any of these messages.
> > >
> > > We are running HSRP on the ethernet interfaces
> that
> > > connect to my LAN. I
> > > believe we are running a 12.0 IOS release,
> although
> > > I am not sure of the
> > > actual version.
> > >
> > > Does anyone have any ideas why this might be
> > > happening? I am trying to
> > > resolve this issue while having no CLI access to
> the
> > > routers. I have been
> > > informed by the controlling body that there are
> no
> > > access lists prohibiting
> > > ICMP messages from being sent, and there are no
> > > firewall rules in place that
> > > would be dropping the ICMP messages.
> > >
> > > Any and all explanations of possible
> > > causes/resolutions would be
> > > appreciated.
> > >
> > > Steve D.
> > >
> > >
> > >
> > >
> > >
> >
> >
> >
>
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