[Re: [[nsp] unroutable?]]

joshua sahala joshua.ej.smith at usa.net
Tue Nov 11 13:29:57 EST 2003

Hank Nussbacher <hank at att.net.il> wrote:

> Ok.  I'll bite: and if a crafted packet comes in with source 127.x.x.x 
> or even better - destined to 127.x.x.x and there is no route entry, no
> cef entry, nada - what does IOS do with the packet?
> -Hank

there is a cef entry (from a 7513 running 12.0(25)S1):

tricksy_router#sho ip route
% Network not in table
tricksy_router#sho ip cef, version 0, epoch 0, attached, default route handler
0 packets, 0 bytes
  via, 0 dependencies
    valid null adjacency

as to what the router does with it, i'm not sure, my bogon filters block
it before it gets to the router (don't yours? ;) ) 

it is an interesting question, will the router (lacking appropriate bogon
and spoofing filters) pass a packet source from 127.x.x.x to a valid
(or invalid) address on the other side of the router - sounds like 
something to play with....


"Walk with me through the Universe,
 And along the way see how all of us are Connected.
 Feast the eyes of your Soul,
 On the Love that abounds.
 In all places at once, seemingly endless,
 Like your own existence."
     - Stephen Hawking -

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