nanog mailing list archives
Re: Request for comment -- BCP38
From: Baldur Norddahl <baldur.norddahl () gmail com>
Date: Mon, 26 Sep 2016 22:08:36 +0200
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.Interesting. But this looks like a feature request for the router vendor, and not like an issue with BCP 38 filtering as such.
Can you quote an RFC for anything that the router is doing wrong? Is there a requirement that a router must support source routing?
In our case we actually did contact the vendor. Turns out that it will do source routing but not for packets from the control plane. There is no way to resolve the issue with the current software available to us. The vendor is not priotizing fixing this as I am also unable to point to any RFC that is being violated.
Even if or when we get a fix, this will continue to be a problem because it is a very common setup. There are thousands of networks out there that have the issue and many of them are probably not even realising it.
It is not a common configuration which was what I said in the text you removed from that quote:From this follows that BCP38 can break things like traceroute and path MTU discovery in what is a very common setup.That doesn't follow. In order to break PMTUD, you also need an MTU drop. Is that a common configuration for routers in points in the network where this would matter?
"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".
Besides it appears that path MTU is broken in general.We accept the problem because the only actual consequence is that traceroute is a little funky.
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)
- Re: Request for comment -- BCP38 Eliot Lear (Sep 26)
- Re: Request for comment -- BCP38 Mark Andrews (Sep 26)