North American Network Operators Group|
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Re: Martian list of IP's to block???
> > deny ip 10.0.0.0 0.255.255.255 any log > > deny ip 172.16.0.0 0.15.255.255 any log > > deny ip 192.168.0.0 0.0.255.255 any log > > These three clauses will block things like ICMP would-fragment and > ttl-expired messages, in the event that some transitory bit of network > between your customer and someone else's customer is numbered using > RFC1918 address space (and causes such messages to be sent). > > I know of several networks which use RFC1918 addresses like this, > in the belief that since the elements with these numbers never > need to receive a packet from anybody outside the operator's network, > there is no need for the numbers to be globally unique. Unfortunately, they're wrong. > In my opinion, such RFC1918 visibility in the public network is > misguided, and half of the disruption to service caused by rules > like those above could be considered just punishment. Agreed. > Trouble is, the other half of the disruption is for your customers, > and you know who they're going to blame if they can't reach their > favourite repository of huge flesh-tone jpegs. > > Operational content: does anybody actually block packets inbound > from off-net, in the case where they are sourced from an RFC1918 > address? If so, do your customers complain? We (UNINETT, AS224) block RFC 1918 source addresses on our border routers, and have been doing so for a couple of years now. We have had zero complaints about this. We certainly intend to continue. Steinar Haug, Nethelp consulting, firstname.lastname@example.org