North American Network Operators Group
Date Prev | Date Next | Date Index | Thread Index | Author Index | Historical

Re: router worms and International Infrastructure

  • From: Matthew Crocker
  • Date: Thu Sep 22 08:53:54 2005 




At your borders (upstream/peers), you will naturally block all of
10/8

at egress.





my border is very broad and it's not feasible to use acls on all
equipment

that makes up that edge :( (for the sake of arguement, which is now
far

afield from the original question: "Feasible path won't stop someone

spoofing space thats in my FIB, will it?"





The solution is a double border, possibly with VRF and inter-VRF
routing



Internal border sees 10/8 and 10/8 is in the FIB. 10/8 packets can
be spoofed here, Infrastructure connects her

External border doesn't see 10/8, 10/8 is NOT in the FIB, 10/8
packets can't be spoofed. Internet connects here.



Internal <-> External links use routable IP space to not infect
external with infrastructure routes.

External border cannot talk to infrastructure IPs but it doesn't need
to.

External can route through infrastructure to customer CPE



10/8 can still be spoofed on the infrastructure but it will have to
come from a customer, not from the Internet.




Also, consider the cases where customers push packets your way (for
uRPF

strict, which isn't available for JunOS, but is for IOS depending on

platform/code/hardware-rev... ugh!) and never send you a route for the

traffic back to them? Maybe they are just a transit and don't even
hear

the routes for their customer who chose a 'cheaper' path that doesn't

include them nor me directly on this link in question?





This sounds like a broken design. Why have one way links? If a
customer pushes packets my way and they don't announce that route to
me I will drop the packets at my edge. If they want to send me those
packets they need to announce. They can announce with AS path
prepend x 1000 so I don't send them any traffic but the route needs
to exist.




"does urpf feasible path stop a 'customer' from spoofing sources
that are

in the FIB?"



No, but you don't use feasible path on links aimed at your customer,
you use strict. If your router doesn't support strict then talk to
your purchasing department.



--

Matthew S. Crocker

Vice President

Crocker Communications, Inc.

Internet Division

PO BOX 710

Greenfield, MA 01302-0710

http://www.crocker.com