How to verify or build a BOGON list

The folks at cymru has a DNSbased BOGON listing that's available to anybody that can execute a AXFR against their DNS-server;

e.g

dig @ns1.cymru.com. axfr bogons.cymru.com. | grep bogons | grep 127.0.0.2


A entry in this DNS listing can then be used to check your BOGON list or you can take the reverse output and convert it to to either a cisco wildcard or cidr format.

e.g

So you can write a ACL listing with confidence to meet your needs;

e.g

deny 169.254.0.0/16
deny 169.254.0.0 0.0.255.255
deny 169.254.0.0 255.255.0.0

 NOTE: great if you need to check the format for a BOGON entry

Ken Felix

Freelance Network / Security Engineer

kfelix  ----a---t---socpuppets ---d---o---t---com

     ^      ^

=(   ^   ^  )=

          o

       /     \

.