This document describes how to configure central web authentication with wired clients connected to switches with the help of Identity Services Engine (ISE).
The concept of central web authentication is opposed to local web authentication, which is the usual web authentication on the switch itself. In that system, upon dot1x/mab failure, the switch will failover to the webauth profile and will redirect client traffic to a web page on the switch.
Central web authentication offers the possibility to have a central device that acts as a web portal (in th is example, the ISE). The major difference compared to the usual local web authentication is that it is shifted to Layer 2 along with mac/dot1x authentication. The concept also differs in that the radius server (ISE in this example) returns special attributes that indicate to the switch that a web redirection must occur. This solution has the advantage to eliminate any delay that was necessary for web authentication to kick. Globally, if the MAC address of the client station is not known by the radius server (but other criteria can also be used), the server returns redirection attributes, and the switch authorizes the station (via MAC authentication bypass [MAB]) but places an access list to redirect the web traffic to the portal. Once the user logs in on the guest portal, it is possible via CoA (Change of Authorization) to bounce the switch port so that a new Layer 2 MAB authentication occurs. The ISE can then remember it was a webauth user and apply Layer 2 attributes (like dynamic VAN assignment) to the user. An ActiveX component can also force the client PC to refresh its IP address.
Cisco recommends that you have knowledge of these topics:
Identity Services Engine (ISE)
Cisco IOS® switch configuration
The information in this document is based on these software and hardware versions:
Cisco Catalyst 3560 Series Switch that runs software version 12.2.55SE3
Note: The procedure is similar or identical for other Catalyst switch models. You can use these steps on all Cisco IOS Software Releases for Catalyst unless stated otherwise.
The information in this document was created from the devices in a specific lab environment. All of the devices used in this document started with a cleared (default) configuration. If your network is live, make sure that you understand the potential impact of any command.
This is not a mandatory step. The redirect ACL sent back with the central webauth profile determines which traffic (HTTP or HTTPS) is redirected to the ISE. The downloadable ACL allows you to define what traffic is allowed. You should typically allow for DNS, HTTP(S), and 8443 and deny the rest. Otherwise, the switch redirects HTTP traffic but allows other protocols.
Complete these steps in order to create the downloadable ACL:
Click Policy, and click Policy Elements.
Expand Authorization, and click Downloadable ACLs.
Click the Add button in order to create a new downloadable ACL.
In the Name field, enter a name for the DACL. This example uses myDACL.
This image shows typical DACL content, which allows:
DNS - resolve the ISE portal hostname
HTTP and HTTPS - allow redirection
TCP port 8443 - serve as the guest portal port
Create the Authorization Profile
Complete these steps in order to create the authorization profile:
Click Policy, and click Policy Elements.
Expand Authorization, and click Authorization profile.
Click the Add button in order to create a new authorization profile for central webauth.
In the Name field, enter a name for the profile. This example uses CentralWebauth.
Choose ACCESS_ACCEPT from the Access Type drop-down list.
Check the Web Authentication check box, and choose Centralized from the drop-down list.
In the ACL field, enter the name of the ACL on the switch that defines the traffic to be redirected. This examples uses redirect.
Choose Default from the Redirect drop-down list.
Check the DACL Name checkbox, and choose myDACL from the drop-down lsit if you decide to use a DACL instead of a static port ACL on the switch.
The Redirect attribute defines whether the ISE sees the default web portal or a custom web portal that the ISE admin created. For example, the redirect ACL in this example triggers a redirection upon HTTP or HTTPS traffic from the client to anywhere. The ACL is defined on the switch later in this configuration example.
Create an Authentication Rule
Complete these steps in order to use the authentication profile to create the authentication rule:
Under the Policy menu, click Authentication.
This image shows an example of how to configure the authentication policy rule. In this example, a rule is configured that triggers when MAB is detected.
Enter a name for your authentication rule. This example uses MAB.
Select the plus (+) icon in the If condition field.
Choose Compound condition, and choose Wired_MAB.
Click the arrow located next to and ... in order to expand the rule further.
Click the + icon in the Identity Source field, and choose Internal endpoints.
Choose Continue from the 'If user not found' drop-down list.
This option allows a device to be authenticated (through webauth) even if its MAC address is not known. Dot1x clients can still authenticate with their credentials and should not be concerned with this configuration.
Create an Authorization Rule
There are now several rules to configure in the authorization policy. When the PC is plugged in, it goes through MAB; it is assumed that the MAC address is not known, so the webauth and ACL are returned. This MAC not known rule is shown in this image and is configured in this section:
Complete these steps in order to create the authorization rule:
Create a new rule, and enter a name. This example uses MAC not known.
Click the plus (+) icon in the condition field, and choose to create a new condition.
Expand the expression drop-down list.
Choose Network Access, and expand it.
Click AuthenticationStatus, and choose the Equals operator.
Choose UnknownUser in the right-hand field.
On the General Authorization page, choose CentralWebauth (Authorization Profile) in the field to the right of the word then.
This step allows the ISE to continue even though the user (or the MAC) is not known.
Unknown users are now presented with the Login page. However, once they enter their credentials, they are presented again with an authentication request on the ISE; therefore, another rule must be configured with a condition that is met if the user is a guest user. In this example, If UseridentityGroup equals Guest is used, and it is assumed that all guests belong to this group.
Click the actions button located at the end of the MAC not known rule, and choose to insert a new rule above.
Note: It is very important that this new rule comes before the MAC not known rule.
Enter a name for the new rule. This example uses IS-a-GUEST.
Choose a condition that matches your guest users.
This example uses InternalUser:IdentityGroup Equals Guest because all guest users are bound to the Guest group (or another group you configured in your sponsor settings).
Choose PermitAccess in the result box (located to the right of the word then).
When the user is authorized on the Login page, ISE restarts a Layer 2 authentication on the switch port, and a new MAB occurs. In this scenario, the difference is that an invisible flag is set for ISE to remember that it was a guest-authenticated user. This rule is 2nd AUTH, and the condition is Network Access:UseCase Equals GuestFlow. This condition is met when the user authenticates via webauth, and the switch port is set again for a new MAB. You can assign any attributes you like. This example assigns a profile vlan90 so that the user is assigned the VLAN 90 in his second MAB authentication.
Click Actions (located at the end of the IS-a-GUEST rule), and choose Insert new rule above.
Enter 2nd AUTH in the name field.
In the condition field, click the plus (+) icon, and choose to create a new condition.
Choose Network Access, and click UseCase.
Choose Equals as the operator.
Choose GuestFlow as the right operand.
On the authorization page, click the plus (+) icon (located next to then) in order to choose a result for your rule.
In this example, a preconfigured profile (vlan90) is assigned; this configuration is not shown in this document.
You can choose a Permit Access option or create a custom profile in order to return the VLAN or attributes that you like.
Enable the IP Renewal (Optional)
If you assign a VLAN, the final step is for the client PC to renew its IP address. This step is achieved by the guest portal for Windows clients. If you did not set a VLAN for the 2nd AUTH rule earlier, you can skip this step.
If you assigned a VLAN, complete these steps in order to enable IP renewal:
Click Administration, and click Guest Management.
Expand Guest, and expand Multi-Portal Configuration.
Click DefaultGuestPortal or the name of a custom portal you may have created.
interface GigabitEthernet1/0/12 description ISE1 - dot1x clients - UCS Eth0 switchport access vlan 100 switchport mode access ip access-group webauth in authentication order mab authentication priority mab authentication port-control auto mab spanning-tree portfast end
VLAN 100 is the VLAN that provides full network connectivity. A default port ACL (named webauth) is applied and defined as shown here:
ip access-list extended webauth permit ip any any
This sample configuration gives full network access even if the user is not authenticated; therefore, you might want to restrict access to unauthenticated users.
In this configuration, HTTP and HTTPS browsing does not work without authentication (per the other ACL) since ISE is configured to use a redirect ACL (named redirect). Here is the definition on the switch:
ip access-list extended redirect deny ip any host <ISE ip address> permit TCP any any eq www permit TCP any any eq 443
This access list must be defined on the switch in order to define on which traffic the switch will perform the redirection. (It matches on permit.) In this example, any HTTP or HTTPS traffic that the client sends triggers a web redirection. This example also denies the ISE IP address so traffic to the ISE goes to the ISE and does not redirect in a loop. (In this scenario, deny does not block the traffic; it just does not redirect the traffic.) If you use unusual HTTP ports or a proxy, you can add other ports.
Another possibility is to allow HTTP access to some web sites and redirect other web sites. For example, if you define in the ACL a permit for internal web servers only, clients could browse the web without authenticating but would encounter the redirect if they try to access an internal web server.
The last step is to allow CoA on the switch. Otherwise, the ISE cannot force the switch to reauthenticate the client.
aaa server radius dynamic-author client <ISE ip address> server-key <radius shared secret>
This command is required for the switch to redirect based on HTTP traffic:
ip http server
This command is required to redirect based on HTTPS traffic:
ip http secure-server
These commands are also important:
radius-server vsa send authentication radius-server vsa send accounting
If the user is not yet authenticated, the show authentication session int <interface num> returns this output:
01-SW3750-access#show auth sess int gi1/0/12 Interface: GigabitEthernet1/0/12 MAC Address: 000f.b049.5c4b IP Address: 192.168.33.201 User-Name: 00-0F-B0-49-5C-4B Status: Authz Success Domain: DATA Security Policy: Should Secure Security Status: Unsecure Oper host mode: single-host Oper control dir: both Authorized By: Authentication Server Vlan Policy: N/A ACS ACL: xACSACLx-IP-myDACL-51519b43 URL Redirect ACL: redirect URL Redirect: https://ISE2.wlaaan.com:8443/guestportal/gateway? sessionId=C0A82102000002D8489E0E84&action=cwa Session timeout: N/A Idle timeout: N/A Common Session ID: C0A82102000002D8489E0E84 Acct Session ID: 0x000002FA Handle: 0xF60002D9
Runnable methods list:
Method State mab Authc Success
Note: Despite a successful MAB authentication, the redirect ACL is placed since the MAC address was not known by the ISE.
Switch Configuration (Full)
This section lists the full switch configuration. Some unnecessary interfaces and command lines have been omitted; therefore, this sample configuration should be used for reference only and should not be copied.
Current configuration : 6885 bytes ! version 15.0 no service pad service timestamps debug datetime msec localtime show-timezone service timestamps log datetime msec localtime show-timezone no service password-encryption ! ! boot-start-marker boot-end-marker ! enable secret 5 $1$xqtx$VPsZHbpGmLyH/EOObPpla. ! aaa new-model ! ! aaa group server radius newGroup ! aaa authentication login default local aaa authentication dot1x default group radius aaa authorization exec default none aaa authorization network default group radius ! ! ! ! aaa server radius dynamic-author client 192.168.131.1 server-key cisco ! aaa session-id common clock timezone CET 2 0 system mtu routing 1500 vtp interface Vlan61 udld enable
dot1x system-auth-control dot1x critical eapol ! ! ! errdisable recovery cause bpduguard errdisable recovery interval 60 ! spanning-tree mode pvst spanning-tree logging spanning-tree portfast bpduguard default spanning-tree extend system-id spanning-tree vlan 1-200 priority 24576 ! vlan internal allocation policy ascending lldp run ! ! ! ! ! ! interface FastEthernet0/2 switchport access vlan 33 switchport mode access authentication order mab authentication priority mab authentication port-control auto mab spanning-tree portfast ! interface Vlan33 ip address 192.168.33.2 255.255.255.0 ! ip default-gateway 192.168.33.1 ip http server ip http secure-server ! ip route 0.0.0.0 0.0.0.0 192.168.33.1 ! ip access-list extended MY_TEST permit ip any any ip access-list extended redirect deny ip any host 192.168.131.1 permit tcp any any eq www permit tcp any any eq 443 ip access-list extended webAuthList permit ip any any ! ip sla enable reaction-alerts logging esm config logging trap warnings logging facility auth logging 10.48.76.31 snmp-server community c3560public RO snmp-server community c3560private RW snmp-server community private RO radius-server host 192.168.131.1 auth-port 1812 acct-port 1813 key cisco radius-server vsa send authentication radius-server vsa send accounting ! ! ! privilege exec level 15 configure terminal privilege exec level 15 configure privilege exec level 2 debug radius privilege exec level 2 debug aaa privilege exec level 2 debug ! line con 0 line vty 0 4 exec-timeout 0 0 password Cisco123 authorization commands 1 MyTacacs authorization commands 2 MyTacacs authorization commands 15 MyTacacs authorization exec MyTacacs login authentication MyTacacs line vty 5 15 ! ntp server 10.48.76.33 end
HTTP Proxy Configuration
If you use an HTTP proxy for your clients, it means that your clients:
Use a unconventional port for HTTP protocol
Send all their traffic to that proxy
In order to have the switch listen on the unconventional port (for example, 8080), use these commands:
ip http port 8080 ip port-map http port 8080
You also need to configure all clients to keep using their proxy but to not use the proxy for the ISE IP address. All browsers include a feature that allows you to enter host names or IP addresses that should not use the proxy. If you do not add the exception for the ISE, you encounter a loop authentication page.
You also need to modify your redirection ACL to permit on the proxy port (8080 in this example).
Important Note about Switch SVIs
At this time, the switch needs a switch virtual interface (SVI) in order to reply to the client and send the web portal redirection to the client. This SVI does not necessarily have to be on the client subnet/VLAN. However, if the switch has no SVI in the client subnet/VLAN, it has to use any of the other SVIs and send traffic as defined in the client routing table. This typically means traffic is sent to another gateway in the core of the network; this traffic comes back to the access switch inside the client subnet.
Firewalls typically block traffic from and to the same switch, as in this scenario, so redirection might not work properly. Workarounds are to allow this behavior on the firewall or to create an SVI on the access switch in the client subnet.
Important Note about HTTPS Redirection
Switches are able to redirect HTTPS traffic. Thus, if the guest client has a homepage in HTTPS, the redirection occurs correctly.
The whole concept of redirection is based upon the fact that a device (in this case, the switch) spoofs the website IP address. However, a major issue arises when the switch intercepts and redirects HTTPS traffic because the switch can present only its own certificate in the Transport Layer Security (TLS) handshake. Since this is not the same certificate as the website originally requested, most browsers issue major alerts. The browsers correctly handle the redirection and presentation of another certificate as a security concern. There is no workaround for this, and there is no way for the switch to spoof your original website certificate.
The client PC plugs in and performs MAB. The MAC address is not known, so ISE pushes the redirection attributes back to the switch. The user tries to go to a website and is redirected.
When the authentication of the Login page is successful, the ISE bounces the switchport through Change Of Authorization, which starts again a Layer 2 MAB authentication.
However, the ISE knows that it is a former webauth client and authorizes the client based on the webauth credentials (although this is a Layer 2 authentication).
In the ISE authentication logs, the MAB authentication appears at the bottom of the log. Although it is unknown, the MAC address was authenticated and profiled, and the webauth attributes were returned. Next, authentication occurs with the user's username (that is, the user types his credentials in the Login page). Immediately after authentication, a new Layer 2 authentication occurs with the username as credentials; this authentication step is where you can return attributes such dynamic VLAN.
There is currently no verification procedure available for this configuration.
There is currently no specific troubleshooting information available for this configuration.