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In App Engine, you can create a firewall with up to 1000 prioritized individual rules that either allow or restrict a range of IP addresses and subnets. Your app will only respond to requests that are allowed by the firewall.
To learn how the App Engine firewall works, see Understanding firewalls.
Before you beginBefore you can create App Engine firewall rules for your app, you must have one of the following App Engine IAM roles, which include the necessary privileges for creating or modifying firewall rules:
Use one of the following methods to create a firewall rule. Repeat these steps for each additional rule:
ConsoleUse the Firewall rules page in Google Cloud console to create a firewall rule:
Go to the Create a firewall rule page in Google Cloud console:
Specify the details of the firewall rule:
Valid values are 1
to 2147483646
. Priority 1
is the first rule evaluated. Priority 2147483647
is the last rule evaluated and is reserved for the `default` rule.
allow
forward the request to the app. Rules set to deny
respond to requests with a 403 Forbidden
error.Run the following gcloud app firewall-rules
commands to create a firewall rule:
Run the following command to create a firewall rule:
gcloud app firewall-rules create PRIORITY --action ALLOW_OR_DENY --source-range IP_RANGE --description DESCRIPTIONwhere:
1
and 2147483646
that defines the rule's importance and order for which the rule is evaluated. Priority 1
is the first rule evaluated. Priority 2147483647
is the last rule evaluated and is reserved for the `default` rule. Important: After a rule is created, you cannot edit the priority value. You must delete and then recreate a rule to change the value of a rule's priority.allow
or deny
. Rules set to allow
forward the request to the app. Rules set to deny
respond to requests with a 403 Forbidden
error.gcloud app firewall-rules test-ip IP_ADDRESSwhere IP_ADDRESS is the IP address that you want to test against your firewall.
gcloud app firewall-rules list
gcloud app firewall-rules delete PRIORITYwhere PRIORITY is the priority value of the rule that you want to delete.
Add a rule that allows an IPv6 address and subnet mask, and then test that rule to ensure it gets evaluated prior to your other rules:
gcloud app firewall-rules create 123 --source-range fe80::3636:3bff:fecc:8778/128 --action allow gcloud app firewall-rules test-ip fe80::3636:3bff:fecc:8778
Add a rule to deny an IPv4 address and subnet mask, and then test that rule to ensure that it gets appropriately evaluated:
gcloud app firewall-rules create 123456 --source-range "74.125.0.0/16" --action deny gcloud app firewall-rules test-ip 74.125.0.8
Update and then test the default rule to ensure that it restricts all IP addresses that don't match any other rules:
gcloud app firewall-rules update default --action deny gcloud app firewall-rules test-ip 123.456.7.89
To programmatically create firewall rules for your App Engine app, you can use the apps.firewall.ingressRules
methods in the Admin API.
To test a firewall rule and ensure that the priority and action provide the expected behavior, you can use the apps.firewall.ingressRules.list
method and specify the IP address that you want to test within the matchingAddress
parameter.
An App Engine firewall consists of an ordered list of rules that can allow or deny access from the specified IP address or range to your app. The rule applies to all resources of the App Engine application.
Firewall rule priorityThe firewall rules are ordered by importance, which you define as a numerical value in each rule's priority. You must specify a unique priority value for each rule as it defines the importance relative to the other rules in the firewall. The values for a rule's priority scale from the most important value of 1
up to the least important at value 2147483647
.
Each firewall includes a default
rule that is automatically created with the 2147483647
priority and applies to the entire IP range of your app. The default
rule is always evaluated after all the other rules in the firewall and applied to all requests across all IP addresses.
The firewall evaluates the highest priority rule first. All the remaining rules in the firewall are sequentially evaluated until a rule matches the IP range of that request. When a matching rule is found, the connection is either allowed or denied, and all the remaining rules in the firewall are then skipped. If none of the manually defined rules in the firewall match the request, the default
rule is evaluated.
For example, if you create a rule with priority 1
it is always evaluated first. If an incoming request matches the rule with priority 1
, only that rule is evaluated and all the other rules in the firewall are skipped, including the default
rule.
The example firewall below shows how a rule's priority can change the behavior of your firewall.
Example firewallIn this example, a company has set up a firewall to grant access to the engineering team and internal corporate network to their in-development app. The firewall rules have been created with large gaps between each priority to allow for growth.
Priority Action IP range Description 1000 Deny 192.0.2.1 Denies access to a DoS attacker. 2000 Allow 198.51.100.2 Allows access to an engineer in the satellite office. 3000 Deny 198.51.100.0/24 Denies access to all non-engineering buildings. 5000 Allow 203.0.113.0/24 Allows access to the main building's network. 2147483647 Deny * Default ActionAfter the firewall is created, assume that the following requests are directed at the sample app and note the app's response:
For example, assume that two of the priorities in the company's firewall are swapped. If the rules for priorities 2000 and 3000 are swapped, notice the unintended behavior.
Priority Action IP range Description 1000 Deny 192.0.2.1 Denies access to a DoS attacker. 2000 Deny 198.51.100.0/24 Denies access to all non-engineering buildings. 3000 Allow 198.51.100.2 Allows access to an engineer in the satellite office. 5000 Allow 203.0.113.0/24 Allows access to the main building's network. 2147483647 Deny * Default ActionThe engineer in the satellite office will not be able to access the company's app as the rule's new priority means it will never be evaluated. The engineer's IP address 198.51.100.2
matches the rule that denies all non-engineers in the range 198.51.100.0/24
before the rule that allows access to the engineer's IP address.
To fix this, you must set the priority of the rule that allows access to 198.51.100.2
to be higher than the rule that denies access for the IP range 198.51.100.0/24
.
To ensure that you've securely configured your app and set the appropriate levels of access, review Application Security as well as Access Control.
Except as otherwise noted, the content of this page is licensed under the Creative Commons Attribution 4.0 License, and code samples are licensed under the Apache 2.0 License. For details, see the Google Developers Site Policies. Java is a registered trademark of Oracle and/or its affiliates.
Last updated 2025-08-07 UTC.
[[["Easy to understand","easyToUnderstand","thumb-up"],["Solved my problem","solvedMyProblem","thumb-up"],["Other","otherUp","thumb-up"]],[["Hard to understand","hardToUnderstand","thumb-down"],["Incorrect information or sample code","incorrectInformationOrSampleCode","thumb-down"],["Missing the information/samples I need","missingTheInformationSamplesINeed","thumb-down"],["Other","otherDown","thumb-down"]],["Last updated 2025-08-07 UTC."],[[["App Engine firewalls utilize prioritized rules to allow or restrict access based on IP addresses or subnets, with up to 1000 individual rules possible per firewall."],["Firewall rules are evaluated in order of priority, from 1 (highest) to 2147483646 (lowest), and a default rule with priority 2147483647 is always evaluated last, affecting all requests not caught by previous rules."],["Each rule specifies an action (allow or deny) and an IP range in CIDR notation, and once a rule matches an incoming request, the action is applied, and the evaluation of the remaining rules is skipped."],["You can create, test, view, and delete firewall rules using the Google Cloud Console or the gcloud command-line tool, and you can programmatically manage rules through the Admin API."],["Priority is unchangeable once a rule is created, and a rule needs to be deleted and recreated if you want to change its priority."]]],[]]
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