Gateway

Cenário

                 +----------------+                          +----------------+
 Zone esternal   |     Gateway    |                          |                |
 Internet  -- >  | enp0s3         |     Zone internal        |  Rede Interna  |
                 |        enp0s8  | <--100.100.200.0/24 -->  |                |         
                 +----------------+                          +----------------+

Regras default

Primeiro vamos listar as regras default:

# firewall-cmd --list-all-zones
block
  interfaces: 
  sources: 
  services: 
  ports: 
  masquerade: no
  forward-ports: 
  icmp-blocks: 
  rich rules: 
 
dmz
  interfaces: 
  sources: 
  services: ssh
  ports: 
  masquerade: no
  forward-ports: 
  icmp-blocks: 
  rich rules: 
 
drop
  interfaces: 
  sources: 
  services: 
  ports: 
  masquerade: no
  forward-ports: 
  icmp-blocks: 
  rich rules: 
 
external
  interfaces: 
  sources: 
  services: ssh
  ports: 
  masquerade: yes
  forward-ports: 
  icmp-blocks: 
  rich rules: 
 
home
  interfaces: 
  sources: 
  services: dhcpv6-client ipp-client mdns samba-client ssh
  ports: 
  masquerade: no
  forward-ports: 
  icmp-blocks: 
  rich rules: 
 
internal
  interfaces: 
  sources: 
  services: dhcpv6-client ipp-client mdns samba-client ssh
  ports: 
  masquerade: no
  forward-ports: 
  icmp-blocks: 
  rich rules: 
 
public (default, active)
  interfaces: enp0s3 enp0s8
  sources: 
  services: dhcpv6-client ssh
  ports: 
  masquerade: no
  forward-ports: 
  icmp-blocks: 
  rich rules: 
 
trusted
  interfaces: 
  sources: 
  services: 
  ports: 
  masquerade: no
  forward-ports: 
  icmp-blocks: 
  rich rules: 
 
work
  interfaces: 
  sources: 
  services: dhcpv6-client ipp-client ssh
  ports: 
  masquerade: no
  forward-ports: 
  icmp-blocks: 
  rich rules:

Como podemos observar, algumas zonas já vem com regras aplicadas, são elas:

# firewall-cmd --list-all --zone=dmz
dmz
  interfaces: 
  sources: 
  services: ssh
  ports: 
  masquerade: no
  forward-ports: 
  icmp-blocks: 
  rich rules:

# firewall-cmd --list-all --zone=external
external
  interfaces: 
  sources: 
  services: ssh
  ports: 
  masquerade: yes
  forward-ports: 
  icmp-blocks: 
  rich rules:

# firewall-cmd --list-all --zone=home
home
  interfaces: 
  sources: 
  services: dhcpv6-client ipp-client mdns samba-client ssh
  ports: 
  masquerade: no
  forward-ports: 
  icmp-blocks: 
  rich rules:

# firewall-cmd --list-all --zone=internal
internal
  interfaces: 
  sources: 
  services: dhcpv6-client ipp-client mdns samba-client ssh
  ports: 
  masquerade: no
  forward-ports: 
  icmp-blocks: 
  rich rules:

# firewall-cmd --list-all --zone=public
public (default, active)
  interfaces: enp0s3 enp0s8
  sources: 
  services: dhcpv6-client ssh
  ports: 
  masquerade: no
  forward-ports: 
  icmp-blocks: 
  rich rules:

# firewall-cmd --list-all --zone=work
work
  interfaces: 
  sources: 
  services: dhcpv6-client ipp-client ssh
  ports: 
  masquerade: no
  forward-ports: 
  icmp-blocks: 
  rich rules:

Removendo asregras default

Agora iremos remove-la pois iremos criar nossas prórias regras

# firewall-cmd --permanent --zone=home --remove-service=dhcpv6-client
# firewall-cmd --permanent --zone=home --remove-service=ipp-client
# firewall-cmd --permanent --zone=home --remove-service=mdns
# firewall-cmd --permanent --zone=home --remove-service=samba-client
# firewall-cmd --permanent --zone=home --remove-service=ssh

# firewall-cmd --permanent --zone=internal --remove-service=dhcpv6-client
# firewall-cmd --permanent --zone=internal --remove-service=ipp-client
# firewall-cmd --permanent --zone=internal --remove-service=mdns
# firewall-cmd --permanent --zone=internal --remove-service=samba-client
# firewall-cmd --permanent --zone=internal --remove-service=ssh

# firewall-cmd --permanent --zone=work --remove-service=dhcpv6-client
# firewall-cmd --permanent --zone=work --remove-service=ipp-client
# firewall-cmd --permanent --zone=work --remove-service=ssh

# firewall-cmd --permanent --zone=public --remove-service=dhcpv6-client
# firewall-cmd --permanent --zone=public --remove-service=ssh

# firewall-cmd --permanent --zone=external --remove-service=ssh
# firewall-cmd --permanent --zone=external --remove-masquerade

# firewall-cmd --permanent --zone=dmz --remove-service=ssh

# firewall-cmd --reload
success

Configuraçãode rede

Listando as interfaces

# nmcli connection show
NOME    UUID                                  TIPO            DISPOSITIVO 
enp0s3  3c36b8c2-334b-57c7-91b6-4401f3489c69  802-3-ethernet  enp0s3      
enp0s8  ab608dc7-afc8-4f77-8cae-5d030ff147b3  802-3-ethernet  enp0s8

# ip addr show
1: lo: <LOOPBACK,UP,LOWER_UP> mtu 65536 qdisc noqueue state UNKNOWN 
    link/loopback 00:00:00:00:00:00 brd 00:00:00:00:00:00
    inet 127.0.0.1/8 scope host lo
       valid_lft forever preferred_lft forever
    inet6 ::1/128 scope host 
       valid_lft forever preferred_lft forever
2: enp0s3: <BROADCAST,MULTICAST,UP,LOWER_UP> mtu 1500 qdisc pfifo_fast state UP qlen 1000
    link/ether 08:00:27:71:22:b3 brd ff:ff:ff:ff:ff:ff
    inet 10.0.2.15/24 brd 10.0.2.255 scope global dynamic enp0s3
       valid_lft 81353sec preferred_lft 81353sec
    inet6 fe80::a00:27ff:fe71:22b3/64 scope link 
       valid_lft forever preferred_lft forever
3: enp0s8: <BROADCAST,MULTICAST,UP,LOWER_UP> mtu 1500 qdisc pfifo_fast state UP qlen 1000
    link/ether 08:00:27:62:50:58 brd ff:ff:ff:ff:ff:ff
    inet 100.100.200.254/24 brd 100.100.200.255 scope global enp0s8
       valid_lft forever preferred_lft forever
    inet6 fe80::a00:27ff:fe62:5058/64 scope link 
       valid_lft forever preferred_lft forever

Alterando as zonas default

A zona que vem ativa por padrão é public

# firewall-cmd --get-default-zone
public

Vamos deixar a interface enp0s3 na zona external coma mascaramento (masquerade) e a interface enp0s8 na zona internal que colocaremos como default.

# nmcli c m enp0s8 connection.zone internal

# firewall-cmd --set-default-zone=internal
success
# firewall-cmd --reload
success

# firewall-cmd --list-all --zone=internal
internal (active)
  interfaces: enp0s8
  sources: 
  services: 
  ports: 
  masquerade: no
  forward-ports: 
  icmp-blocks: 
  rich rules:

# nmcli c m enp0s3 connection.zone external

]# firewall-cmd --permanent --zone=external --add-masquerade
success
# firewall-cmd --reload
success

# firewall-cmd --list-all --zone=external
external (active)
  interfaces: enp0s3
  sources: 
  services: 
  ports: 
  masquerade: yes
  forward-ports: 
  icmp-blocks: 
  rich rules:

Aplicando regras

Com a remoção dessas regras naturalmente perdemos o acesso aonosso firewall. Então vamos liberar o acesso por ssh.

# firewall-cmd --permanent --zone=internal --add-service=ssh
success
# firewall-cmd --permanent --zone=external --add-service=ssh
success
# firewall-cmd --reload
success

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