IPv4 Router Alert Option

Fri May 23 19:35:02 UTC 2008

On Fri, May 23, 2008 at 3:30 PM,  <Valdis.Kletnieks at vt.edu> wrote:
> On Fri, 23 May 2008 15:00:02 EDT, Ron Bonica said:
>> Folks,
>>
>> It is my belief that many ISPs, will not accept datagrams containing the
>> Router Alert IP option from customers. Do I have that right?
>>
>> I am asking so that I might better evaluate Internet drafts that would
>> require ISPs to accept such packets.
>
> What you're likely to find in *reality* is that ISPs will be more than happy
> to pass the packets along, but the corporate/consumer firewalls in place

s/pass the packets/pass the packets that don't harm their network devices/

> at the ISP's *customers* will stomp on the options (see all the ways that
> mismanaged firewalls fail to do ingress/egress filtering of rfc1918 packets,
> or think "ICMP Frag Needed" means "This ICMP needs to be fragged", or...).
>
> And it doesn't really matter if it's the ISP or the end site that screws it
> up - if it gets thrown away, it gets thrown away.
>
> Unless you had an ISP-specific use for Router Alert, where end-customer
> behavior doesn't matter?

router-alert is blocked in many places, I believe (I'm fuzzy on this)
that some vendors allow you to ignore router-alert, which I think is
the preferred option for this option.

-Chris