[c-nsp] Missing 'packet-too-big' ICMPs on 12.2(28)SB6

[Gerald Krause]

Gert Doering wrote:
> Hi,
> 
> On Mon, Sep 10, 2007 at 08:55:35PM +0200, Gerald Krause wrote:
>> The only problem with our config could be the fact that we have
>> configured a MTU of 1530 byte (because of MPLS) on the FEs. But even
>> if this could be problematic I would expect that in the case that a
>> paket arrive which can't be delivered through the VirtualInterfaces
>> (MTU 1448 byte) the system have to mention that in the logging buffer.
>> Thats why I have enabled ICMP debugging and related CEF debugging
>> but I never see 'packet-too-big' ICMP messages, only 'echo' and
>> 'host/port unreachable' messages are logged. But I See that CEF is
>> aware of the fact that it can't deliver the packet without
>> fragmentation:
> 
> I've seen massive problems with IPv6 MTU and CEF on a 7301 with 
> 12.2(31)SB2 - short version: the router seems to incorrectly count
> the size of the header, and drops packets bigger than 1482 bytes
> (1500 - 18 byte ethernet header).
> 
> No ICMP either, packet just gone.

Sigh, I thought about testing 12.2(31)SB7 but now I'am afraid that
wouldn't help me. Thx!

--
Gerald   (ax/tc)