nanog mailing list archives
Re: Request for comment -- BCP38
From: Baldur Norddahl <baldur.norddahl () gmail com>
Date: Mon, 26 Sep 2016 21:05:28 +0200
Den 26. sep. 2016 18.02 skrev "Mike Hammett" <nanog () ics-il net>:
The only asymmetric routing broken is when the source isn't in public
Internet route-able space. That just leaves those multi-ISP WAN routers that NAT it. Some of our IP transits implement filtering. All of our transits assigned /30 subnets on the transit ports from their own range (the alternate would have be to ask us to supply the /30 from our pool). Our provider edge router will send back ICMP packets using the interface address from the interface that received the original packet. It will then route the packet using our normal routing table. This means we can receive some packet on transit port A and then route out a ICMP response on port B using the interface address from port A. But transit B filters this ICMP packet because it has a source address belonging to transit A.
From this follows that BCP38 can break things like traceroute and path MTU
discovery in what is a very common setup. The only reason we do not have a bigger problem is that few networks will have a downward MTU change at this point in the network. Regards Baldur
Current thread:
- Request for comment -- BCP38 Stephen Satchell (Sep 26)
- Re: Request for comment -- BCP38 Paul Ferguson (Sep 26)
- Re: Request for comment -- BCP38 Ken Chase (Sep 26)
- Re: Request for comment -- BCP38 Hugo Slabbert (Sep 26)
- Re: Request for comment -- BCP38 Laszlo Hanyecz (Sep 26)
- Re: Request for comment -- BCP38 Mike Hammett (Sep 26)
- Re: Request for comment -- BCP38 Baldur Norddahl (Sep 26)
- Re: Request for comment -- BCP38 Florian Weimer (Sep 26)
- Re: Request for comment -- BCP38 Baldur Norddahl (Sep 26)
- Re: Request for comment -- BCP38 Florian Weimer (Sep 27)
- Re: Request for comment -- BCP38 Jason Iannone (Sep 27)
- Re: Request for comment -- BCP38 Florian Weimer (Sep 27)
- Re: Request for comment -- BCP38 Stephen Satchell (Sep 27)
- Re: Request for comment -- BCP38 Florian Weimer (Sep 27)
- Re: Request for comment -- BCP38 Ken Chase (Sep 26)
- Re: Request for comment -- BCP38 Paul Ferguson (Sep 26)
- Re: Request for comment -- BCP38 Aled Morris (Sep 26)
- Re: Request for comment -- BCP38 John Levine (Sep 26)
- Re: Request for comment -- BCP38 Laszlo Hanyecz (Sep 26)