Level-3 (routing) cont..
1/4 of Class-B network is shielded from external Internet (IFZ)
1/4 of IR2 subnet is shielded from other SLAC subnets (SFZ)
BSD subnets accessed via internal gateway
MCC subnets accessed via internal gateways
Critical MCC realtime network not routed - has dual-homed hosts to regulate access