Network Login Overview

Network login controls the admission of user packets into a network by allowing MAC addresses from users that are properly authenticated. Network login is controlled on a per-port basis.

When network login is enabled on a port, that port does not forward any packets until authentication takes place.

Unknown broadcast/unicast/multicast (BUM) traffic is not allowed on the egress side of network login-enabled ports until authentication is successful. To allow BUM traffic to egress on network login-enabled, unauthenticated ports, use configure netlogin ports [port_list | all] allow egress-traffic [none | unicast | broadcast | all_cast] .

Network login is capable of three types of authentication: web-based, MAC-based, and 802.1X. In addition, network login has two different modes of operation: campus mode and ISP mode. The authentication types and modes of operation can be used in any combination.

When web-based network login is enabled on a switch port, that port is placed into a non-forwarding state until authentication takes place. To authenticate, a user must open a web browser and provide the appropriate credentials. These credentials are either approved, in which case the port is placed in forwarding mode, or not approved, in which case the port remains blocked. You can initiate user logout by submitting a logout request or closing the logout window.

The following capabilities are included with network login:
  • Web-based login using HTTP available on each port.

  • Web-based login using HTTPS.

  • Multiple supplicants for web-based, MAC-based, and 802.1X authentication on each port.

ExtremeXOS NetLogin provides the AAA (Authentication, Authorization, and Accounting) functionality, which is an important block of the network infrastructure and security and provides a model or framework to determine who is requesting network access, network resources that can be accessed by the requesting party, and when the resources are used. NetLogin supports all popular methods of authentication: MAC-based, Web-based, and IEEE 802.1X. NetLogin can help network administrators to control access into the network; it also provides flexibility to configure specific backend resources to which user access is allowed.

Together with IP Security, administrators can enhance security in the network by controlling access to upstream network and resources by the hosts or clients. IP Security is a collection of powerful features that allow network administrators to design security in combination with standard authentication and authorization techniques. IP Security features as ExtremeXOS 15.2 include:
  • DHCP Snooping and concept of trusted DHCP Servers

  • Source IP Lockdown

  • ARP Learning and Validation

  • Gratuitous ARP Protection

When NetLogin and IP Security features are enabled on a port, NetLogin performs the first or the basic function of authenticating and authorizing the user. Further course of action is determined by IP Security in case a violation is detected. The violation action will then determine further access to the network.
Scenario Notes Expected Behavior

NetLogin + DHCP Snooping and trusted DHCP Servers/Ports.

Violation: DHCP Server Packets seen on netlogin enabled ports (i.e. a host is masquerading post authentication).

We recommend that you enable NetLogin on the client-facing ports. Enabling DHCP Snooping on all ports, including client/host facing ports and ports connected to the upstream network automation and provisioning infrastructure, ensures that all DHCP messages are processed by the switch and a DHCP binding database is maintained.

For the combination of NetLogin and DHCP Security to work correctly, we recommend that you configure at least one uplink (or server facing port) as a trusted port. This ensures that all other ports (normally client-facing ports) automatically become untrusted, and can be monitored for any violations that might occur. You can configure more than one uplink port as "trusted" as this allows flexibility in network design.

In addition to controlling which DHCP Servers can communicate with the downstream clients, the trusted DHCP Server configuration can be used.

Action: None

NetLogin authenticates the client, and IP Security flags a violation. No action is taken because of configuration.

Action: Drop-packet

The packet is dropped, and an EMS event is logged.

Action: block-mac

NetLogin initially authenticates the client, and subsequently when the violation occurs, IP Security reports violation, which causes the MAC address to be blocked either permanently or for a configured duration on the switch. The FDB will be flushed after FDB entry ages out and the netlogin entry is unauthenticated and removed from the switch.

Action: block-port

NetLogin initially authenticates the client, and subsequently when the violation occurs, IP Security reports the violation, which causes the port to be administratively disabled. As a result, all authenticated clients on the ports are immediately unauthenticated and removed from the switch. This can occur either for a certain configured duration or permanently.

We do not recommend that you use this configuration if there are multiple supplicants on the port (for example, conference rooms, groups of users, etc. accessing the network through an intermediate port extender, or hub).

In addition, for network troubleshooting and debugging purposes, an SNMP trap can be sent to a central network manager such as Extreme Management Center or Ridgeline.

NetLogin + Source IP Lockdown

Violation: After a client/host successfully authenticates to the network, it performs a source IP address violation.

The Source IP lockdown feature can determine if a client/host should be allowed access to the network based on inspection of the source IP address used in the packets. If a client is not using an IP address present in DHCP binding database, a violation is flagged for the client and further action is determined by configuration.

This helps prevent clients from using source addresses not assigned by a centralized network automation and provisioning infrastructure.

By default the switch denies all IP traffic from clients when source IP lockdown is enabled. In order for the clients to get a valid IP address, DHCP packets are allowed to be forwarded through the switch. NetLogin authentication (all three forms) will still proceed, and clients presenting the valid credentials (per authentication scheme) are authenticated. Post authentication (and authorization - for membership to a VLAN), once a valid DHCP binding is found for the client, access control lists are automatically (dynamically) applied to permit traffic from the client.

It is not mandatory to configure specific violation actions in DHCP Snooping (which is a prerequisite to this feature).

If configured, DHCP Snooping filters and violation actions take precedence over source IP lockdown. This is to ensure that successfully authenticated clients (with NetLogin) do not masquerade as rogue DHCP servers post authentication. In this case, DHCP violation is detected and actions are determined per configuration for vilation-action.

NetLogin + DHCP Secured ARP

DHCP Secured ARP allows administrators to control how the ARP table is populated. By default, the switch learns IP ARP bindings and builds the ARP table by tracking the ARP requests and replies. When DHCP Secured ARP is used for design, IP ARP learning method can be disabled. This is recommended for security purposes.

When combined with NetLogin, this feature ensures that a client (even after success authentication) cannot override the ARP entry on the switch, thereby preventing duplicate addresses and ensuring proper network operation.

ARP entries populated from DHCP are known as Secure ARP entries and are flushed/removed only when the address is released.

Same behavior as expected in the case of "NetLogin + DHCP Snooping and Trusted Ports/Server". Apart from securing the IP ARP table, in this case, violations detected as part of DHCP Snooping and validation is flagged and actions are determined by configuration.

NetLogin + ARP Validation

ARP Validation helps check different fields in the ARP packet. Source MAC, Destination MAC, and Source IP addresses can be checked for validity.

For a complete reference to the different checks performed, please refer to ARP Validation Options.

All checks are performed post authentication.

Violation actions are same as the options presented in the DHCP Snooping and Validation Cases.

Same expected behavior and functionality as in the case of "NetLogin + DHCP Snooping and Trusted Ports/Server".

NetLogin + Gratuitous ARP Protection

Gratuitous ARP is a method by which a client/host can resolve its own IP address, and is useful in scenarios where duplicate addresses need to be detected, or a host can announce that it has either used an IP address on a different NIC card, or even if a client has moved from one location to another.

While ExtremeXOS supports Gratuitous ARP, protection can also be enabled to mitigate any risk or threats that can arise because of any m-i-m attacks. The switch will automatically send ARP packets to not only protect its own IP address but to also safeguard addresses of any NetLogin authenticated clients on the switch. For this, it is recommended that both DHCP Secured ARP and Gratuitous ARP protection be enabled on the switch.

It is not mandatory that DHCP Snooping be enabled for this feature, but becomes a prerequisite if DHCP Secured ARP is also configured.

ARP Packets are sent out when a violation is detected.

For all other violations detected by DHCP Snooping and Trust, the corresponding violation actions are determined by configuration, and expected behavior is the same as the case of "NetLogin + DHCP Snooping and Trusted Servers/Ports".