On Fri, 23 May 2008, Ron Bonica wrote:
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.
Depends on what you mean by the word "accept." Transit backbone operators have been changing to the position of protecting their router CPU's from user packets being punted up the control plane. If they can forward the packet without going up the control plane, I think most transit backbones will "accept" the packet and ignore IP options like Router Alert. If someone writes a standard to require ISPs to do something besides ignore an IP option and forward the packet, then you may see ISPs drop packets instead of punting them to the control plane. For example, packets with IP Source Route options. Router# conf t Router(config)# ip options ignore Router(config)# exit Router# write mem As Chris mentions, packets with IP options are likely to have more problems crossing firewalls/security devices or even simple NAT/middle-boxes. I don't remember who, but someone once suggested if we could go back in time to the late 1970's and redo the Internet Protocol we would get rid of all IP options and made IP addresses 64 bits and classless from the beginning.