At 07:36 AM 10/25/00, Donohue, Steve wrote:
>I found this link as well that is why I am wondering about the lack of ICMP
>messages. I realize that when you enable HSRP on an interface it disables
>ICMP redirects. Would the ICMP messages requesting a smaller MTU size fall
>under this category?
No (unless there's a bug, which I haven't heard is the case)
>Thanks again all.
>
>Steve
>
>-----Original Message-----
>From: Phil Barker [mailto:[EMAIL PROTECTED]]
>Sent: Wednesday, October 25, 2000 7:22 AM
>To: Gareth Hinton; [EMAIL PROTECTED]
>Subject: Re: Not receiving ICMP messages
>
>
>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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