Network Security
Uses for External Dynamic Lists in Policy
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Uses for External Dynamic Lists in Policy
An External Dynamic List is a text file that is hosted on an external web server so that
your configuration can import objects—IP addresses, URLs, and domains. Additionally for
PAN-OS & Panorama, International Mobile Equipment Identities (IMEIs) and
International Mobile Subscriber Identities (IMSIs)—included in the list and enforce
policy. To enforce Security policy on the entries included in the external dynamic list,
you must reference the list in a supported security rule or profile. When multiple lists
are referenced, you can prioritize the order of evaluation to make sure the most
important EDLs are committed before capacity limits are reached. As you modify the list,
the list dynamically imported at the configured interval and enforces policy without the
need to make a configuration change or a commit. If the web server is unreachable, the
last successfully retrieved list is used for enforcing policy until the connection is
restored with the web server. In cases where authentication to the EDL fails, the
Security policy stops enforcing the EDL. To retrieve the external dynamic list, the
interface configured with the Palo Alto Networks Services service
route is used.
Your configuration retains the last successfully retrieved EDL and continues operating
with the most current EDL information until connection is restored with the server
hosting the EDL if:
- You upgrade or downgrade your environment
- You reboot your environment, management plane, or data plane
- The server hosting the EDL becomes unreachable
These types of external dynamic lists are supported:
- Predefined IP Address—A predefined IP address list is a type of IP address list that refers to the built-in, dynamic IP lists with fixed or “predefined” contents. These Configure Your Environment to Access an External Dynamic List—for bulletproof hosting providers, known malicious, and high-risk IP addresses—are automatically added to your configuration if you have an active Threat Prevention license. A predefined IP address list can also refer to an EDL that uses one of the built-in lists as a source. Because you can’t modify the contents of a predefined list, you can use a predefined list as a source for a different EDL if you want to add or exclude list entries.
- Predefined URL List—This type of external dynamic list contains pre-populated URLs that applications use for background services, such as updates or Certificate Revocation List (CRL) checks, that can safely be excluded from Authentication policy. Palo Alto Networks revises and maintains this type of external dynamic list, which is also known as an Authentication Portal Exclude List, through content updates.
- IP Address—Your environment typically enforces policy for a source or destination IP address that is defined as a static object on the device (see Enforce Policy on an External Dynamic List). If you need agility in enforcing policy for a list of source or destination IP addresses that emerge ad hoc, you can use an external dynamic list of type IP address as a source or destination address object in security rules, deny or allow access to the IP addresses (IPv4 and IPv6 address, IP range and IP subnets) included in the list. You can also use an IP address EDL in the source or destination of an SD-WAN security rule. An external dynamic list of type IP address is treated as an address object; all the IP addresses included in a list are handled as one address object.
- Domain—This type of external dynamic list allows you to import custom domain names to enforce policy using an Anti-Spyware profile or SD-WAN policy rule. An EDL in an Anti-Spyware profile is very useful if you subscribe to third-party threat intelligence feeds and want to protect your network from new sources of threat or malware as soon as you learn of a malicious domain. For each domain you include in the external dynamic list, a custom DNS-based spyware signature is created so that you can enable DNS sinkholing. The DNS-based spyware signature is of type spyware with medium severity and each signature is named Custom Malicious DNS Query <domain name>. You can choose to include the subdomains of a specifed domain. For example, if your domain list includes paloaltonetworks.com, all lower level components of the domain name (e.g., *.paloaltonetworks.com) will also be included as part of the list. When this setting is enabled, each domain in a given list requires an additional entry, effectively doubling the number of entries used by the list. For details on configuring domain lists, see configure DNS sinkholing for a custom list of domains.
- URL—This type of external dynamic list gives you the agility to protect your network from new sources of threat or malware. An external dynamic list with URLs are handled like a custom URL category and you can use this list in two ways:
- As a match criterion in Security rules, Decryption security rules, and QoS security rules to allow, deny, decrypt, not decrypt, or allocate bandwidth for the URLs in the custom category.
- In a URL Filtering profile where you can define more granular actions, such as continue, alert, or override, before you attach the profile to a Security rule (see Use an External Dynamic List in a URL Filtering Profile).
- (PAN-OS & Panorama Only) Equipment Identity—You can reference an external dynamic list of IoT devices defined by International Mobile Equipment Identities (IMEIs) in a Security rule that controls traffic for equipment connected to a 5G or 4G network. Refer to the Mobile Network Infrastructure Getting Started for information about configuring Equipment ID security on supported device models.
- (PAN-OS & Panorama Only) Subscriber Identity—You can reference an external dynamic list of International Mobile Subscriber Identities (IMSIs) in a Security rule that controls traffic for subscribers connected to a 5G or 4G network. Refer to the Mobile Network Infrastructure Getting Started for information about configuring Subscriber ID security on supported device models.
(PAN-OS & Panorama Only) On each device model, you can add up to a maximum
of 30 custom EDLs with unique sources that can be used to enforce policy. The external dynamic list
limit is not applicable to Panorama. When using Panorama to manage a device that is
enabled for multiple virtual systems, if you exceed the limit for the device, a commit
error displays on Panorama. A source is a URL that includes the IP address or hostname,
the path, and the filename for the external dynamic list. The device matches the URL
(complete string) to determine whether a source is unique.
While the device does not impose a limit on the number of lists of a specific type, the
following limits are enforced:
- IP address—The PA-3200 Series, PA-5200 Series, and the PA-7000 Series devices support a maximum of 150,000 total IP addresses; all other models support a maximum of 50,000 total IP addresses. No limits are enforced for the number of IP addresses per list. When the maximum supported IP address limit is reached, the a syslog message is generated. The IP addresses in predefined IP address lists do not count toward the limit.
- URL and domain—The maximum number of URLs and domains supported varies by model. No limits are enforced for the number of URL or domain entries per list. Refer to the following table for specifics on your model:Model
URL List Entry Limits Domain List Entry Limits PA-5200 Series, PA-5400 Series, PA-7000 Series (upgraded with the PA-7000 20GXM NPC, PA-7000 20GQXM NPC, or the PA-7000 100G NPC). PA-7000 appliances with mixed NPCs only support the standard capacities.250,000 4,000,000 VM-500, VM-700100,0002,000,000 PA-400 Series (excepting the PA-410), PA-850, PA-820, PA-3200 Series, PA-3400 Series100,0001,000,000 VM-300100,000500,000 PA-220, PA-410, VM-50, VM-50 (Lite), VM-100, VM-1000-HV50,00050,000
List entries only count toward the limits if they belong to an external dynamic list that
is referenced in policy.
- (Panorama Only) When parsing the list, entries that do not match the list type are skipped, and ignores entries that exceed the maximum number supported for the model. To ensure that the entries do not exceed the limit, check the number of entries currently used in policy. Select ObjectsExternal Dynamic Lists and click List Capacities.
- An external dynamic list must contain entries. If you want to stop using the list, remove the reference from the security rule or profile instead leaving the list blank. If the list does not contain any entries, the list can't be refreshed and so the last information retrieved is used.
- As a best practice, Palo Alto Networks recommends using shared EDLs when multiple virtual systems are used. Using individual EDLs with duplicate entries for each virtual system uses more memory, which might over-utilize device resources.
- EDL entry counts on devices operating multi-virtual systems take additional factors into account (such as DAGs, number of virtual systems, rules bases) to generate a more accurate capacity consumption listing. This might result in a discrepancy in capacity usage after upgrading from PAN-OS 8.x releases.
- Depending on the enabled features, memory usage limits might be exceeded before EDL capacity limits are met due to memory allocation updates. As a best practice, Palo Alto Networks recommends reviewing EDL capacities and, when necessary, removing or consolidating EDLs into shared lists to minimize memory usage.