[c-nsp] what the heck is "ip forward-protocol nd" good for

Sebastian Beutel sebastian.beutel at rus.uni-stuttgart.de
Thu Apr 7 14:20:54 EDT 2016

Hi Phil,
hi List,

On Thu, Apr 07, 2016 at 01:03:24PM +0100, Phil Mayers wrote:
> On 06/04/16 17:16, Sebastian Beutel wrote:
> >What do you think: Is this a bug?
> As others have said: IOS defaults are, largely, insane for 2016.
> We have:
> no ip forward-protocol nd
> no ip forward-protocol udp tftp
> no ip forward-protocol udp nameserver
> no ip forward-protocol udp domain
> no ip forward-protocol udp time
> no ip forward-protocol udp netbios-ns
> no ip forward-protocol udp netbios-dgm
> no ip forward-protocol udp tacacs
> ...amongst other things in our standard IOS config.
> It's one more tedious part of modern IT - reaping the "benefits" of
> compatibility with the very best the 1980s had to offer.
To me the "Cisco IOS IP Application Services Command Reference" is a little


If i get it right, enabling an ip helper on an interfaces enables forwarding
of a list of stuff. Furthermore the global "ip forward-protocol udp"
(without any protocol name) enables forwarding all of this on any interface.
I suppose, that it's very naive to assume, that the lines you wrote could be
replaced by this:

no ip forward-protocol udp
ip forward-protocol udp bootpc
ip forward-protocol udp bootps

But the thing that keeps me puzzled is, that only "ip forward-protocol nd" appears 
in a "sho run" of a default virgin configuration and none of the above does.
Not even in a "sho run {all|full}. Why exactly this and none of the others? 

Best, Sebastian.

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