WAN edge: PAT to the internet, DHCP for the LAN and an inbound guard ACL.
hostname branch-rtr-01
!
interface GigabitEthernet0/0
description WAN
ip address dhcp
ip nat outside
ip access-group WAN_IN in
no shutdown
!
interface GigabitEthernet0/1
description LAN
ip address 10.50.0.1 255.255.255.0
ip nat inside
no shutdown
!
ip dhcp excluded-address 10.50.0.1 10.50.0.50
!
ip dhcp pool LAN
network 10.50.0.0 255.255.255.0
default-router 10.50.0.1
dns-server 1.1.1.1
lease 0 8
!
access-list 10 permit 10.50.0.0 0.0.0.255
ip nat inside source list 10 interface GigabitEthernet0/0 overload
!
ip access-list extended WAN_IN
remark Allow return traffic for sessions we started
permit tcp any any established
permit udp any eq domain any
permit icmp any any echo-reply
permit icmp any any unreachable
remark Path MTU discovery breaks without unreachables above
deny ip any any log
!
end