Should routers send redirects by default?

Eric J. Katanich ekat at onyxlight.net
Fri Aug 20 20:08:17 CDT 2010


On Fri, 20 Aug 2010 13:20:58 -0400, Christopher Morrow  
<christopher.morrow at gmail.com> wrote:
> Polling a little bit here, there's an active discussion going on
> 6man at ietf about whether or not v6 routers should:
>   o be required to implement ip redirect functions (icmpv6 redirect)
>   o be sending these by default
...
> In ipv4 there's a relatively widely used practice of disabling ip
> redirects.

I think it's almost universally disabled (by default) everywhere in IPv4  
purely for security (traffic interception.)  In a perfectly run network,  
redirects should never be necessary, so I'd think IPv6 should avoid going  
down that road again. (support OPTIONAL, never enabled by default.) [It's  
another insecure mistake IPv6 doesn't need to repeat.]

As I recall from long long ago, Cisco IOS would deal with traffic  
differently depending on redirects... with redirects enabled, a redirect  
was sent and the packet dropped; with redirects disabled, the router  
hairpined the packets.  I honestly don't know what today's versions do  
because I've never checked -- A can ping B, I move on.  I turn redirects  
off on *outside* interfaces.  Inside (trustable) interfaces vary -- I  
don't go out of my way to disable them.

--Ricky



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