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url-route-overview.md

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title description services author ms.service ms.date ms.author ms.topic
Azure Application Gateway URL-based content routing overview
This article provides an overview of the Azure Application Gateway URL-based content routing, UrlPathMap configuration and PathBasedRouting rule.
application-gateway
greg-lindsay
application-gateway
01/14/2022
greglin
conceptual

URL Path Based Routing overview

URL Path Based Routing allows you to route traffic to back-end server pools based on URL Paths of the request.

One of the scenarios is to route requests for different content types to different backend server pools.

In the following example, Application Gateway is serving traffic for contoso.com from three back-end server pools for example: VideoServerPool, ImageServerPool, and DefaultServerPool.

imageURLroute

Requests for http://contoso.com/video/* are routed to VideoServerPool, and http://contoso.com/images/* are routed to ImageServerPool. DefaultServerPool is selected if none of the path patterns match.

Important

For both the v1 and v2 SKUs, rules are processed in the order they are listed in the portal. The best practice when you create path rules is to have the least specific path (the ones with wildcards) at the end. If wildcards are on the top, then they take priority even if there's a more specific match in subsequent path rules.

If a basic listener is listed first and matches an incoming request, it gets processed by that listener. However, it's highly recommended to configure multi-site listeners first prior to configuring a basic listener. This ensures that traffic gets routed to the right back end.

UrlPathMap configuration element

The urlPathMap element is used to specify Path patterns to back-end server pool mappings. The following code example is the snippet of urlPathMap element from template file.

"urlPathMaps": [{
    "name": "{urlpathMapName}",
    "id": "/subscriptions/{subscriptionId}/../microsoft.network/applicationGateways/{gatewayName}/urlPathMaps/{urlpathMapName}",
    "properties": {
        "defaultBackendAddressPool": {
            "id": "/subscriptions/    {subscriptionId}/../microsoft.network/applicationGateways/{gatewayName}/backendAddressPools/{poolName1}"
        },
        "defaultBackendHttpSettings": {
            "id": "/subscriptions/{subscriptionId}/../microsoft.network/applicationGateways/{gatewayName}/backendHttpSettingsCollection/{settingname1}"
        },
        "pathRules": [{
            "name": "{pathRuleName}",
            "properties": {
                "paths": [
                    "{pathPattern}"
                ],
                "backendAddressPool": {
                    "id": "/subscriptions/{subscriptionId}/../microsoft.network/applicationGateways/{gatewayName}/backendAddressPools/{poolName2}"
                },
                "backendHttpsettings": {
                    "id": "/subscriptions/{subscriptionId}/../microsoft.network/applicationGateways/{gatewayName}/backendHttpSettingsCollection/{settingName2}"
                }
            }
        }]
    }
}]

PathPattern

PathPattern is a list of path patterns to match. Each path must start with / and may use * as a wildcard character. The string fed to the path matcher doesn't include any text after the first ? or #, and those chars aren't allowed here. Otherwise, any characters allowed in a URL are allowed in PathPattern.

Path rules are case insensitive.

Path pattern Is supported?
/images/* yes
/images* yes
/images/*.jpg no
/*.jpg no
/Repos/*/Comments/* no
/CurrentUser/Comments/* yes

Examples

Path-based rule processing when wildcard (*) is used:

Example 1:

/master-dev* to contoso.com

/master-dev/api-core/ to fabrikam.com

/master-dev/* to microsoft.com

Because the wildcard path /master-dev* is present above more granular paths, all client requests containing /master-dev are routed to contoso.com, including the specific /master-dev/api-core/. To ensure that the client requests are routed to the appropriate paths, it's critical to have the granular paths above wildcard paths.

Example 2:

/ (default) to contoso.com

/master-dev/api-core/ to fabrikam.com

/master-dev/api to bing.com

/master-dev/* to microsoft.com

All client requests with the path pattern /master-dev/* are processed in the order as listed. If there's no match within the path rules, the request is routed to the default target.

For more information, see Resource Manager template using URL-based routing.

PathBasedRouting rule

RequestRoutingRule of type PathBasedRouting is used to bind a listener to a urlPathMap. All requests that are received for this listener are routed based on policy specified in urlPathMap. Snippet of PathBasedRouting rule:

"requestRoutingRules": [
    {

"name": "{ruleName}",
"id": "/subscriptions/{subscriptionId}/../microsoft.network/applicationGateways/{gatewayName}/requestRoutingRules/{ruleName}",
"properties": {
    "ruleType": "PathBasedRouting",
    "httpListener": {
        "id": "/subscriptions/{subscriptionId}/../microsoft.network/applicationGateways/{gatewayName}/httpListeners/<listenerName>"
    },
    "urlPathMap": {
        "id": "/subscriptions/{subscriptionId}/../microsoft.network/applicationGateways/{gatewayName}/urlPathMaps/{urlpathMapName}"
    }

}
    }
]

Next steps

After learning about URL-based content routing, go to create an application gateway using URL-based routing to create an application gateway with URL routing rules.