[j-nsp] Re: ICMPv6 "packet too big" not being emitted

[Daniel Roesen]

On Tue, Jan 10, 2006 at 07:46:24PM +0100, Daniel Roesen wrote:
> The configured tunnel MTU is correct, but the router doesn't emit the
> necessary ICMPv6 "packet too big".

The observed problem sounds remarkably like this one:
http://www.atm.tut.fi/list-archive/juniper-nsp-2005/msg02391.html
which went without any interest from Juniper.

The problematic router's backbone uplinks are indeed unnumbered ATM
PVCs, unlike the other routers I've tested which have POS/GigE uplinks.
The "mtu exceeded" counter of "show pfe statistics ip6 icmp" is
confirmed to NOT increase when receiving packets which are too large for
the tunnel.

Juniper: I'm pretty sure you have a serious problem with handling
packets which would need fragmentation, being received on unnumbered
links, in IPv4 and IPv6. Would you eventually care to open a PR about
that this time, even if not submitted via sales channels or support
contract? Should be in your best interest to get it fixed. :-)

The problem with IS-IS mishandling unnumbered ethernet links in IPv6 is
also still pending AFAIK. Looks like "running unnumbered" is dangerous
on JunOS (and I always recommend against it for various reasons, the
dangers of that kind being one of them).


Best regards,
Daniel

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