I actually have one 1800 configured as follow. this config is running well and all needed routing and port publishing are functioning.
Ip assignment to interfaces:
int ATM0.1: a.a.a.a pointtopoint address
int VLAN1: 192.168.39.247 (internal network address) as secondary address
int VLAN1: b.b.b.b public ip address
Actually internal network is connected to Eth6
interface FastEthernet0 no ip address duplex auto speed auto ! interface BRI0 no ip address encapsulation hdlc shutdown ! interface FastEthernet1 ! interface FastEthernet2 ! interface FastEthernet3 ! interface FastEthernet4 ! interface FastEthernet5 ! interface FastEthernet6 ! interface FastEthernet7 ! interface FastEthernet8 ! interface ATM0 no ip address no atm ilmi-keepalive dsl operating-mode auto ! interface ATM0.1 point-to-point ip address a.a.a.a 255.255.255.252 ip nat outside ip virtual-reassembly no snmp trap link-status pvc 8/35 oam-pvc manage oam retry 5 5 1 encapsulation aal5snap ! ! interface Vlan1 ip address 192.168.39.247 255.255.255.0 secondary ip address b.b.b.b 255.255.255.252 ip nat inside ip virtual-reassembly ip tcp adjust-mss 1452 hold-queue 100 out ! ip route 0.0.0.0 0.0.0.0 ATM0.1 ! ! no ip http server no ip http secure-server ip nat inside source list 1 interface Vlan1 overload ip nat inside source static tcp 192.168.39.225 22 interface Vlan1 222 ip nat inside source static tcp 192.168.39.225 443 interface Vlan1 443 ip nat inside source static tcp 192.168.39.225 80 interface Vlan1 80 ! logging trap notifications logging 192.168.39.214 access-list 1 permit 192.168.39.0 0.0.0.255
Studying documentation i found other possible configurations to accomplish the same result so i'd like to know what's the most right and why. My doubt are about which is the most correct interface(s) to use.
1) Assignment of public ip address (b.b.b.b) to a different interface instead of assign it as secondary address on vlan1 interface
2) Possible use of loopback interface for public o private ip
3) Possible use of eth0 for private ip
4) Possibile use of one eth (1-8) for private ip. These interfaces cannot be assigned an Ip because are layer 2. vlan or loopback must be used to use these interfaces?