1.Set interfaces.

user@host# set interfaces ge-0/0/0 unit 0 family inet address 1.2.2.1/24
user@host# set interfaces fe-1/0/0 unit 0 family inet address 1.1.1.1/24
user@host# set security zones security-zone zone_dmz interfaces ge-0/0/0.0
user@host# set security zones security-zone zone_external interfaces fe-1/0/0.0

2.Define addresses.

user@host# set security zones security-zone zone_dmz address-book address ws1 1.2.2.10/32
user@host# set security zones security-zone zone_dmz address-book address ws2 1.2.2.20/32
user@host# set security zones security-zone zone_dmz address-book address ws3 1.2.2.30/32
user@host# set security zones security-zone zone_dmz address-book address ws4 1.2.2.40/32
user@host# set security zones security-zone zone_dmz address-book address-set web_servers address ws1
user@host# set security zones security-zone zone_dmz address-book address-set web_servers address ws2
user@host# set security zones security-zone zone_dmz address-book address-set web_servers address ws3
user@host# set security zones security-zone zone_dmz address-book address-set web_servers address ws4

3.Configure policy.

user@host# set security policies from-zone zone_external to-zone zone_dmz policy id_1 match source-address any
user@host# set security policies from-zone zone_external to-zone zone_dmz policy id_1 match destination-address web_servers
user@host# set security policies from-zone zone_external to-zone zone_dmz policy id_1 match application junos-http
user@host# set security policies from-zone zone_external to-zone zone_dmz policy id_1 then permit

4.Configure SCREEN options.

user@host# set security screen ids-option zone_external-syn-flood tcp syn-flood alarm-threshold 250
user@host# set security screen ids-option zone_external-syn-flood tcp syn-flood attack-threshold 625
user@host# set security screen ids-option zone_external-syn-flood tcp syn-flood source-threshold 25
user@host# set security screen ids-option zone_external-syn-flood tcp syn-flood timeout 20
user@host# set security zones security-zone zone_external screen zone_external-syn-flood