Very old thread! Private hosts can communicate with all other hosts inside the enterprise, both public and private. However, they cannot have IP connectivity to any host outside of the enterprise. All other hosts will be public and will use globally unique address space assigned by an Internet Registry. Then you have the policy that its best to filter any rfc1918 packets ingress which then leads on to broken path mtu, missing traceroute hops... etc.. for the tiny number of addresses you need on p2p why does your boss care. Steve On Fri, 15 Nov 2002, Steve Rude wrote:

Hi All,

I am trying to collect information about using RFC 1918 space on an ISP backbone. I have read the RFC several times, and I don't see where it says that you cannot use 10/8 space to number your backbone links (/30s).

I know this is an old thread that has been rehashed several times, but can anyone please send me links or information that I can use to convince my boss that we should use our arin alloc'd space on our backbone instead of using private space.

Also if anyone has opinions on naming conventions for backbone such as why to or why not to even have dns resolution for your backbone and some conventions please let me know.

TIA!

-- Steve Rude steve@rudedogg.com

Generally it is not prohibited by the RFC, but it is bad form if you send out ICMP that originates from 10space to places outside your network. As such, it's generally bad form to use these numbers on intefaces in the backbone, since those interfaces are likely to show up in ICMP time exceeded messages unless you completely block traceroute through your backbone, which is generally regarded as far worse form. Owen --On Friday, November 15, 2002 15:33 -0800 Steve Rude <steve@rudedogg.com> wrote:

Hi All,

I am trying to collect information about using RFC 1918 space on an ISP backbone. I have read the RFC several times, and I don't see where it says that you cannot use 10/8 space to number your backbone links (/30s).

I know this is an old thread that has been rehashed several times, but can anyone please send me links or information that I can use to convince my boss that we should use our arin alloc'd space on our backbone instead of using private space.

Also if anyone has opinions on naming conventions for backbone such as why to or why not to even have dns resolution for your backbone and some conventions please let me know.

TIA!

-- Steve Rude steve@rudedogg.com

haesu@towardex.com wrote:

You could also use RFC1918 numbers for your point-to-point /30 aggregation blocks with the customers.. But.. since that would have effect on customer's premise equipment, it would be better to give them globally unique space as well, who knows if your customer comes back and yells at you for not being able to get to his router's serial interface IP.

This practice was implemented here in the early days, before I came along. There have been almost no requests to change by clients, and very, very few who even noticed/cared enough to ask why. But as more VPNs are deployed, I've seen this break some implementations. So for two reasons we've begun the (large) task of renumbering all the /30 ptp links either public or unnumbered: 1) Ensures all clients who decide to implement VPN don't run into frustration because of this practice. We want to encourage better security practices, and VPN can be an integral part of that. 2) The script kiddies won't mistakenly assume that we're not doing source address filtering. I'm sure that seeing a private address in traceroute probably makes you a more desirable target in certain circles. There is only one case where I would recommend using a private address on a public link. We have a client periodically attacked, and in some cases the attackers have simultaneously attacked our own infrastructure. They now have only one path to them here, and every hop past the border is RFC1918.