# Firewall Terminology

## Router

### machine has 2 interfaces, makes routing & policy decisions

### may be unix host with IP forwarding, or dedicated hardware

## Packet Filter

### Prevent unwanted packets from passing

### Allow selectively

### May redirect to inside

## Proxy (aka application gateway)

### Can forward around filter

#### Listens on one interface

### Needed if

#### forwarding off

#### nat/masquerading for multi-connection protocols (ftp, icq, H323)