-----Original Message----- From: owner-nanog@merit.edu [mailto:owner-nanog@merit.edu] On Behalf Of David Schwartz Sent: Wednesday, May 17, 2006 1:37 PM To: nanog@nanog.org Subject: RE: private ip addresses from ISP
Our router is running BGP and connecting to our upstream provider with /30 network. Our log reveals that there are private IP addresses reaching our router's interface that is facing our upstream ISP. How could this be possible? Should upstream ISP be blocking private IP address according to standard configuration? Could the packet be stripped and IP be converted somehow during the transition? It happens in many Tier-1 ISP though !
Thank you for your information
Do you mean:
1) You are seeing BGP routes for addresses inside private space?
2) You are seeing packets with destination IPs inside private space arriving at your interface from your ISP?
3) You are seeing packets with source IPs inside private space arriving at your interface from your ISP?
If 1, feel free to filter them. You ISP probably uses them internally and is leaking them to you. Feel free to complain if you want.
If 2, make sure you aren't advertising routes into RFC1918 space to your ISP. If not, you should definitely ask them what's up.
If 3, that's normal. These are packets your ISP received that are addressed to you and the ISP is leaving to you the decision of whether to accept them or not. Feel free to filter them out if you wish. (It won't break anything that's not already broken.) Sorry to dig this up from last week but I have to strongly disagree with
From RFC 1918 Because private addresses have no global meaning, routing information about private networks shall not be propagated on inter-enterprise
point #3. links, and packets with private source or destination addresses should not be forwarded across such links. Routers in networks not using private address space, especially those of Internet service providers, are expected to be configured to reject (filter out) routing information about private networks. The ISP shouldn't be "leaving" anything to the end-user, these packets should be dropped as a matter of course, along with any routing advertisements for RFC 1918 space(From #1). ISP's who leak 1918 space into my network piss me off, and get irate phone calls for their trouble. Andrew