New router feature - icmp error source-interface [was: icmp rpf]

Mark Smith nanog at
Mon Sep 25 21:22:16 UTC 2006

On Mon, 25 Sep 2006 09:22:34 -0400
"Patrick W. Gilmore" <patrick at> wrote:

> On Sep 25, 2006, at 9:06 AM, Ian Mason wrote:
> > ICMP packets will, by design, originate from the incoming interface  
> > used by the packet that triggers the ICMP packet. Thus giving an  
> > interface an address is implicitly giving that interface the  
> > ability to source packets with that address to potential anywhere  
> > in the Internet. If you don't legitimately announce address space  
> > then sourcing packets with addresses in that space is (one  
> > definition of) spoofing.
> Who thinks it would be a "good idea" to have a knob such that ICMP  
> error messages are always source from a certain IP address on a router?

I do.


        "Sheep are slow and tasty, and therefore must remain constantly
                                   - Bruce Schneier, "Beyond Fear"

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