Merit Network
Can't find what you're looking for? Search the Mail Archives.
  About Merit   Services   Network   Resources & Support   Network Research   News   Events   Home

Discussion Communities: Merit Network Email List Archives

North American Network Operators Group

Date Prev | Date Next | Date Index | Thread Index | Author Index | Historical

Re: NSPs filter?

  • From: Stephen Stuart
  • Date: Thu Aug 08 21:50:24 2002

> 	One thing that sometimes comes up is that people do number links using 
> RFC1918 address space which occasionally results in an ICMP 'fragmentation 
> needed but DF bit set' packet with an RFC1918 source address. Filtering out 
> this packet could result in TCP breaking.

That can be accomodated; behold, all the joy of PMTUD, with none of
the other crap from designated special-use address space:

firewall {
    family inet {
        filter external-filter {
            term allow-icmp-unreach {
                from {
		    protocol icmp;
		    icmp-type unreachable;
                    icmp-code fragmentation-needed;
                }
                then {
                    count allow-icmp-need-frag;
                    accept;
                }
            }
            term allow-icmp-timxceed {
                from {
		    protocol icmp;
		    icmp-type time-exceeded;
                    icmp-code [ ttl-eq-zero-during-transit ttl-eq-zero-during-reassembly ];
                }
                then {
                    count allow-icmp-timxceed;
                    accept;
                }
            }
            term deny-rfc1918 {
                from {
                    source-address {
                        10.0.0.0/8;
                        172.16.0.0/12;
                        192.168.0.0/16;
                    }
                }
                then {
                    count deny-rfc1918;
                    discard;
                }
            }
            term deny-test {
                from {
                    source-address {
                        192.0.2.0/24;
                    }
                }
                then {
                    count deny-test-net;
                    discard;
                }
            }
            term deny-autoconfig {
                from {
                    source-address {
                        169.254.0.0/16;
                    }
                }
                then {
                    count deny-autoconfig;
                    discard;
                }
            }
	    term LAST {
                then accept;
            }
        }
    }
}

Application is left as an exercise to the reader.

Stephen




Discussion Communities


About Merit | Services | Network | Resources & Support | Network Research
News | Events | Contact | Site Map | Merit Network Home


Merit Network, Inc.