What is the best way to download a snapshot of the Internet's IPv4 routing table? I need check if IP addresses are routable. It needs to function offline, so a looking glass server won't work. I know the table changes frequent
Internet routing table is avilable in every regional internet registry routers.
You can get it at for example: https://www.ripe.net/analyse/internet-measurements/routing-information-service-ris/ris-raw-data
Of course, there isn’t something like „all internet routes”. Available routes depends on your point in the network. Route table in amsterdam will be different than table in for example new york.