Network : Network > Address Objects

Working with Dynamic Addresses
From its inception, SonicOS has used Address Objects (AOs) to represent IP addresses in most areas throughout the user interface. Address Objects come in the following varieties:
Host – An individual IP address, netmask and zone association.
MAC (original) – Media Access Control, or the unique hardware address of an Ethernet host. MAC AOs are used for:
MAC AOs were originally not allowable targets in other areas of the management interface, such as Access Rules, so historically they could not be used to control a host’s access by its hardware address.
Range – A starting and ending IP address, inclusive of all addresses in between.
Group – A collection of Address Objects of any assortment of types. Groups may contain other Groups, Host, MAC, Range, or FQDN Address Objects.
SonicOS redefined the operation of MAC AOs, and supports Fully Qualified Domain Name (FQDN) AOs:
MAC – SonicOS resolves MAC AOs to an IP address by referring to the ARP cache on the firewall.
FQDN – Fully Qualified Domain Names, such as ‘www.reallybadWebsite.com’, will be resolved to their IP address (or IP addresses) using the DNS server configured on the firewall. Wildcard entries are supported through the gleaning of responses to queries sent to the sanctioned DNS servers.
While more effort is involved in creating an Address Object than in simply entering an IP address, AOs were implemented to complement the management scheme of SonicOS, providing the following characteristics:
Zone Association – When defined, Host, MAC, and FQDN AOs require an explicit zone designation. In most areas of the interface (such as Access Rules) this is only used referentially. The functional application are the contextually accurate populations of Address Object drop-down lists, and the area of “VPN Access” definitions assigned to Users and Groups; when AOs are used to define VPN Access, the Access Rule auto-creation process refers to the AO’s zone to determine the correct intersection of VPN [zone] for rule placement. In other words, if the “192.168.168.200 Host” Host AO, belonging to the LAN zone was added to “VPN Access” for the “Trusted Users” User Group, the auto-created Access Rule would be assigned to the VPN LAN zone.
Management and Handling – The versatilely typed family of Address Objects can be easily used throughout the SonicOS interface, allowing for handles (e.g. from Access Rules) to be quickly defined and managed. The ability to simply add or remove members from Address Object Groups effectively enables modifications of referencing rules and policies without requiring direct manipulation.
Reusability – Objects only need to be defined once, and can then be easily referenced as many times as needed.
Key Features of Dynamic Address Objects
The term Dynamic Address Object (DAO) describes the underlying framework enabling MAC and FQDN AOs. By transforming AOs from static to dynamic structures Firewall > Access Rules can automatically respond to changes in the network.
 
For example, creating an FQDN AO for “*.myspace.com” will first use the DNS servers configured on the firewall to resolve “myspace.com” to 63.208.226.40, 63.208.226.41, 63.208.226.42, and 63.208.226.43 (as can be confirmed by nslookup myspace.com or equivalent). Since most DNS servers do not allow zone transfers, it is typically not possibly to automatically enumerate all the hosts in a domain. Instead, the firewall will look for DNS responses coming from sanctioned DNS servers as they traverse the firewall. So if a host behind the firewall queries an external DNS server which is also a configured/defined DNS server on the firewall, the firewall will parse the response to see if it matches the domain of any wildcard FQDN AOs.
FQDN Address Objects are resolved using the DNS servers configured on the firewall in the Network > DNS page. Since it is common for DNS entries to resolve to multiple IP addresses, the FQDN DAO resolution process will retrieve all of the addresses to which a host name resolves, up to 256 entries per AO. In addition to resolving the FQDN to its IPs, the resolution process will also associate the entry’s TTL (time to live) as configured by the DNS administrator. TTL will then be honored to ensure the FQDN information does not become stale.
FQDN Address Objects are resolved using the DNS servers configured on the firewall in the Network > DNS page. Since it is common for DNS entries to resolve to multiple IP addresses, the FQDN DAO resolution process will retrieve all of the addresses to which a host name resolves, up to 256 entries per AO. In addition to resolving the FQDN to its IPs, the resolution process will also associate the entry’s TTL (time to live) as configured by the DNS administrator. TTL will then be honored to ensure the FQDN information does not become stale.
Enforcing the Use of Sanctioned Servers on the Network
Although not a requirement, it is recommended to enforce the use of authorized or sanctioned servers on the network. This practice can help to reduce illicit network activity, and will also serve to ensure the reliability of the FQDN wildcard resolution process. In general, it is good practice to define the endpoints of known protocol communications when possible. For example:
Using MAC and FQDN Dynamic Address Objects
MAC and FQDN DAOs provide extensive Access Rule construction flexibility. MAC and FQDN AOs are configured in the same fashion as static Address Objects, that is from the Network > Address Objects page. Once created, their status can be viewed by a mouse‑over of their appearance, and log events will record their addition and deletion.
Dynamic Address Objects lend themselves to many applications. The following are just a few examples of how they may be used. Future versions of SonicOS may expand their versatility even further.
Blocking All Protocol Access to a Domain using FQDN DAOs
There might be instances where you wish to block all protocol access to a particular destination IP because of non-standard ports of operations, unknown protocol use, or intentional traffic obscuration through encryption, tunneling, or both. An example would be a user who has set up an HTTPS proxy server (or other method of port-forwarding/tunneling on “trusted” ports like 53, 80, 443, as well as nonstandard ports, like 5734, 23221, and 63466) on his DSL or cable modem home network for the purpose of obscuring his traffic by tunneling it through his home network. The lack of port predictability is usually further complicated by the dynamic addressing of these networks, making the IP address equally unpredictable.
Since these scenarios generally employ dynamic DNS (DDNS) registrations for the purpose of allowing users to locate the home network, FQDN AOs can be put to aggressive use to block access to all hosts within a DDNS registrar.
Assumptions
The DSL home user is registering the hostname moosifer.dyndns.org with the DDNS provider DynDNS. For this session, the ISP assigned the DSL connection the address 71.35.249.153.
Step 1 – Create the FQDN Address Object
From Network > Address Objects, select Add and create the following Address Object:
Step 2 – Create the Firewall Access Rule
From the Firewall > Access Rules page, LAN->WAN zone intersection, Add an Access Rule as follows:
NOTE: Rather than specifying LAN Subnets as the source, a more specific source could be specified, as appropriate, so that only certain hosts are denied access to the targets.
Using an Internal DNS Server for FQDN-based Access Rules
It is common for dynamically configured (DHCP) network environments to work in combination with internal DNS servers for the purposes of dynamically registering internal hosts – a common example of this is Microsoft’s DHCP and DNS services. Hosts on such networks can easily be configured to dynamically update DNS records on an appropriately configured DNS server (for example, see the Microsoft Knowledgebase article How to configure DNS dynamic updates in Windows Server 2003 at http://support.microsoft.com/kb/816592/en-us).
The following illustrates a packet dissection of a typical DNS dynamic update process, showing the dynamically configured host 10.50.165.249 registering its full hostname bohuymuth.moosifer.com with the (DHCP provided) DNS server 10.50.165.3:
In such environments, it could prove useful to employ FQDN AOs to control access by hostname. This would be most applicable in networks where hostnames are known, such as where hostname lists are maintained, or where a predictable naming convention is used.
Controlling a Dynamic Host’s Network Access by MAC Address
Since DHCP is far more common than static addressing in most networks, it is sometimes difficult to predict the IP address of dynamically configured hosts, particularly in the absence of dynamic DNS updates or reliable hostnames. In these situations, it is possible to use MAC Address Objects to control a host’s access by its relatively immutable MAC (hardware) address.
Like most other methods of access control, this can be employed either inclusively, for example, to deny access to/for a specific host or group of hosts, or exclusively, where only a specific host or group of hosts are granted access, and all other are denied. In this example, we will illustrate the latter.
Assuming you had a set of DHCP-enabled wireless clients running a proprietary operating system which precluded any type of user-level authentication, and that you wanted to only allow these clients to access an application-specific server (e.g. 10.50.165.2) on your LAN. The WLAN segment is using WPA-PSK for security, and this set of clients should only have access to the 10.50.165.2 server, but to no other LAN resources. All other wireless clients should not be able to access the 10.50.165.2 server, but should have unrestricted access everywhere else.
Step 1 – Create the MAC Address Objects
From Network > Address Objects, select Add and create the following Address Object (multi-homing optional, as needed):
Once created, if the hosts are present in the firewall’s ARP cache, they will be resolved immediately, otherwise they will appear in an unresolved state in the Address Objects table until they are activated and are discovered through ARP:
Step 2 – Create the Firewall Access Rules
To create access rules, navigate to the Firewall > Access Rules page, click on the All Rules radio button, and scroll to the bottom of the page and click the Add button.
 
Bandwidth Managing Access to an Entire Domain
Streaming media is one of the most profligate consumers of network bandwidth. But trying to control access, or manage bandwidth allotted to these sites is difficult because most sites that serve streaming media tend to do so off of large server farms. Moreover, these sites frequently re-encode the media and deliver it over HTTP, making it even more difficult to classify and isolate. Manual management of lists of servers is a difficult task, but wildcard FQDN Address Objects can be used to simplify this effort.
Step 1 – Create the FQDN Address Object
From Network > Address Objects, select Add and create the following Address Object:
Upon initial creation, youtube.com will resolve to IP addresses 208.65.153.240, 208.65.153.241, 208.65.153.242, but after an internal host begins to resolve hosts for all of the elements within the youtube.com domain, the learned host entries will be added, such as the entry for the v87.youtube.com server (208.65.154.84).
Step 2 – Create the Firewall Access Rule
From the Firewall > Access Rules page, LAN->WAN zone intersection, add an Access Rule as follows:
NOTE: If you do not see the Bandwidth tab, you can enable bandwidth management by declaring the bandwidth on your WAN interfaces.
NOTE: The BWM icon appears within the Access Rule table, indicating that BWM is active and providing statistics. Access to all *.youtube.com hosts, using any protocol, is now be cumulatively limited to 2% of your total available bandwidth for all user sessions.