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SSID Modes for Client IP Assignment

The Client IP assignment section of the Wireless > Configure > Access control page controls how clients will be placed on the wired network and get an IP address when associating.

This article describes each of the client IP assignment options available, how they impact clients, and recommended use cases.

Bridge Mode

In bridge mode, the Meraki APs act as bridges, allowing wireless clients to obtain their IP addresses from an upstream DHCP server.

Bridge mode should be enabled when any of the following is true:

  • Wired and wireless clients in the network need to reach each other (e.g., a wireless laptop needs to discover the IP address of a network printer, or wired desktop needs to connect to a wireless surveillance camera).
  • Layer 2 multicast and broadcast packets (e.g., ARP, Bonjour) need to propagate in a limited manner to both wired and wireless clients for device discovery, networking, etc.
  • The wireless network needs to support legacy VPN clients (i.e., those that do not support NAT Traversal).
  • Wired and wireless clients need to have IP addresses in the same subnet for monitoring and/or access control reasons (e.g., a web gateway in the network allows/denies Internet access based on the client’s IP address).
  • Wireless traffic needs to be VLAN-tagged between the Meraki AP and the upstream wired infrastructure. 
  • If IPv6 is used on the network. More information on IPv6 bridging can be found within this article.

 

The implications of enabling bridge mode are as follows:

  • An administrator cannot enable adult content filtering on the SSID. Because the adult content filtering feature is DNS-based, bridge mode disables adult content filtering by using the DNS server(s) advertised by the network’s DHCP server.

  • Multiple DHCP servers are allowed, but they must assign IP addresses to wireless clients from the same subnet. This enables these IP addresses to be routed by the LAN to which the Meraki APs are connected. 

Use Cases

Bridge mode works well in most circumstances, particularly for seamless roaming, and is the simplest option to put wireless clients on the LAN. Layer 3/7 firewall rules and traffic shaping can be used to restrict client traffic before it can reach the wired network, and VLAN tagging can be used to put wireless clients on a specific subnet upstream.

Diagram

In the example below, note that the source IP address of the client traffic remains the same after transparently passing through the access point.

Additional Info

For information on how to apply VLAN tags to wireless client traffic with a bridge SSID, please refer to our documentation.

NAT Mode

In NAT mode, the Meraki APs run as DHCP servers to assign IP addresses to wireless clients out of a private 10.x.x.x IP address pool behind a NAT.

NAT mode should be enabled when any of the following is true:

  • Wireless clients associated to the SSID only require Internet access, not access to local wired or wireless resources. 
  • There is no DHCP server on the LAN that can assign IP addresses to the wireless clients.

  • There is a DHCP server on the LAN, but it does not have enough IP addresses to assign to wireless clients

 

The implications of enabling NAT mode are as follows:

  • Devices outside of the wireless network cannot initiate a connection to a wireless client.
  • Wireless clients cannot use Layer 2 discovery protocols to find other devices on either the wired or wireless network.
  • Legacy VPN clients (i.e., those that do not support NAT Traversal) may not be able to establish IPSec tunnels over the wireless network. (One workaround is to upgrade the VPN client or configure the VPN client to establish an IPSec tunnel over TCP, e.g. SSL.) 
  • VLAN Tagging wireless traffic is not supported in NAT mode.  

Please note that each AP will NAT to its own management IP address. As a result, LAN flows will be interrupted when the client roams between APs.

The DHCP service for NAT mode will only hand out addresses in the 10.0.0.0/8 subnet. SSIDs in NAT mode can still be used on wired networks already using a 10.x.x.x address space, however clients on the NAT SSID may be unable to communicate with these networks.

Use Cases

NAT mode works well for providing a wireless guest network, since it puts clients on a private wireless network with automatic addressing. Layer 3 firewall rules can also be used to quickly limit or block access to network resources.

Diagram

In this example, note that while the client has an address in the 10.0.0.0/8 network, the source IP is altered to the IP address of the access point upon entering the LAN.

Additional Info

For more information on NAT mode, please refer to our documentation:

Layer 3 Roaming

Layer 3 roaming is a built in feature that allows seamless roam even when changing to an AP on a different VLAN. This feature doesn't require a concentrator which eliminates bottlenecks within the network. The Access Points will create a connection from current AP back to the starting AP if the originating VLAN is not present on the target AP. Configure Distributed Layer 3 roaming on the Access Control page. More information on layer 3 roaming architectures are available in the Meraki Layer 3 Roaming Solution Guide.

 

The Layer 3 roaming test will alert of any potential upstream network issues that may prevent the feature from establishing tunnels between access points. 

Use Cases

Distributed Layer 3 roaming is best for large networks with a large number of mobile clients. This mode will provide a more seamless experience, ensuring that clients seamlessly roam across layer 3 boundaries.

Diagram

In this example, the client initially connects at point 1 where its traffic is bridged onto the network. As the client roams to points 2 and 3 and associates to new access points, those access points will first tunnel the traffic back to the initial AP, and then bridge onto the network. All tunneling is done directly between APs.

Additional Resources

For more information about Layer 3 roaming, please refer to our documentation.

Layer 3 Roaming with a Concentrator

Layer 3 roaming allows a client device to maintain a consistent IP address as it roams across APs located in different VLANs. By maintaining a consistent IP address, a client can ensure uninterrupted access to latency sensitive applications such as VoIP.

It is possible to enable layer 3 roaming for Meraki MR access points by creating a secure mobility tunnel from each access point to a Mobility Concentrator, which can be either a VPN Concentrator or an MX security appliance. More information on layer 3 roaming architecture are available in the Meraki Layer 3 Roaming Solution Guide.

This configuration is designed for use with an MX in passthrough/concentrator mode, tunneling to an MX in NAT mode is not supported. 

Use Cases

Layer 3 roaming with a concentrator is most helpful for networks with a moderate number of mobile clients. This mode will provide a more seamless experience. 

Diagram

In this example, the client initially connects at point 1, then roams to points 2 and 3. At each point, the client's traffic is tunneled to the concentrator and then bridged onto the network. 

Configuring a Mobility Concentrator

It is possible to configure either an MX security appliance or a Virtual Concentrator to act as a Mobility Concentrator for layer 3 roaming. Instructions on how to configure a virtual concentrator are available here, documentation regarding the MX security appliance can be found here.

 

Once your Mobility Concentrator is online and connected to the network, be sure to place the MX or VPN concentrator in Passthrough mode:

Setting the SSID to L3 Roaming

After configuring a Mobility Concentrator, an SSID can be configured to concentrate traffic:

  1. Create an SSID to be used for L3 roaming on the Wireless > Configure > Overview page.
  2. Select Layer 3 roaming with a concentrator under Wireless > Configure > Access control > Client IP assignment.
  3. Select the previously created Mobility Concentrator under the Concentrator menu.
  4. Layer 3 roaming clients can be tagged with a specific VLAN under the VLAN tagging option.
    Screen_Shot_2015-07-09_at_11.01.17_PM.png

VPN: Tunnel Data to a Concentrator

Meraki Teleworker VPN enables administrators to extend the corporate LAN to employees at remote sites with Meraki AP’s without requiring client devices to have client VPN software installed and running. The experience of wireless clients connected to remote AP’s will be the same as though they were located at headquarters, with full corporate network access.  

The SSID can be configured to be in full tunnel or split tunnel mode depending on the targeted network design:

 

This configuration is designed for use with an MX in passthrough/concentrator mode, tunneling to an MX in NAT mode is not supported. 

Use Cases

Teleworker VPN can be used to connect small branch offices, teleworker or executive home offices, temporary site offices (eg. construction sites) and traveling employees on the road back to the corporate LAN and provide access to corporate resources back at headquarters. 

Diagram

In this example, the client's traffic is passed through the secure VPN tunnel over the Internet to the VPN concentrator, before then being bridged onto the network there.

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Last modified
11:34, 22 Jan 2016

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ID: 1561

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