You cannot assign multiple IPs on the outside interface but you can NAT Network Address Translate multiple Public IPs and forward all the traffic that commes to that public IP on a DMZ or other Network Node.
It is also possible for forward all traffic that comes on a specific port example TCP 80.
examples:
NAT example:
access-list acl_outside remark Permit any host to access WWW-Server with http
access-list acl_outside permit tcp any host WWW-Public eq www
access-list acl_outside remark Permit any host to access SMTP-Server with smtp
access-list acl_outside permit tcp any host SMTP-Public eq smtp
access-group acl_outside in interface outside
static (dmz,outside) WWW-Public WWW-DMZ netmask 255.255.255.255 0 0
static (dmz,outside) SMTP-Public SMTP-DMZ netmask 255.255.255.255 0 0
PAT example:
access-list acl_out permit tcp any host PIXOutsideIP eq http
access-group acl_out in interface outside
static (inside,outside) tcp PIXOutsideIP http InsideWWW-IP http netmask 255.255.255.255 0 0
Cisco example:
Establishing Connectivity:
http://www.cisco.com/en/US/products/sw/secursw/ps2120/products_configuration_guide_chapter09186a0080172786.html
Config examples PIX:
http://www.cisco.com/en/US/products/hw/vpndevc/ps2030/prod_configuration_examples_list.html
sincerely
Patrick
