Intranet
Extranet
Internet
DMZ
VPN
HTTP
DHCP
Passive router
PPTP
L2TP with IPSec
SSTP
CHAP
501
1723
1701
443
Packet filtering
Stateful packet inspection
NAT filtering
Application-level gateway
Stateless packet inspection
Stateful packet inspection
NAT filtering
Application-level gateway
NAT server
Stateful packet inspector
Proxy server
NIDS
NIDS
NIPS
Internet content filter
NAT server
NIDS
NIPS
Internet content filter
NAT server
Back-to-back configuration
Three-leg perimeter configuration
Basic configuration
Perimeter configuration
1.0
1.1
2.0
3.0
IPSec
MPPE
HTTPS
MSC-CHAP
Proxy server
Application firewall
NAT filtering
Circuit-level gateway
Internet content filter
NIDS
Circuit-level gateway
NAT filtering
Multiple content filters
A master firewall that all traffic flows through
A NAT firewall and a proxy server
Layers
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