This article will introduce you Wireless Mesh Networking on Meraki wifi device.
In the wireless mesh model, multiple APs (with or without Ethernet connections) communicate over wireless interfaces to form a single network. Wireless communication between APs is called Mesh Networking. Meraki’s mesh networking functionality is automated, self-healing, and available on all APs.
1. Components of Mesh Network:
– In Mesh Network, APs can be in one of two states: Gateway, or Repeater.
+ Gateway: Gateway access points are directly connected to the wired network, it has a link to the Internet. If the Gateway loses its Internet connection, it will search for a nearby Gateway and automatically act as a Repeater, without losing active wireless connections.
– Meraki determines whether a device should be a Gateway or Repeater during startup when the device sends a DHCP request. If it receives a DHCP reply from a device on the wired network, it will assume that it has a valid LAN connection and will become the gateway AP. If a gateway AP cannot access the LAN/upstream router port, the AP will switch to Repeater mode.
+ Repeaters: Repeater access points are not directly connected to a wired network, instead relying on wireless mesh links to access the Internet. As long as the Repeater has power and a good wireless connection (unobstructed, etc.) with another Repeater or Gateway, it will form mesh links. Note that it is not possible to configure a static IP address for the Repeater AP, doing so will automatically designate the device as the Gateway instead of the Repeater.
– Both Gateway and Repeater can serve wireless clients. There can be multiple Gateways in a mesh network and Repeaters will automatically choose the Gateway that has the strongest connection.
2. Identify Repeater AP and Gateway AP:
– Go Wireless > Monitor > Access points.
– Click on the wrench icon on the right hand side and ensure that the Gateway option is selected.
– Gateway AP will be listed as “(self)” in the Gateway column.
– Additionally, you can identify the Repeater or Gateway AP by checking the LAN IP section on the AP’s detail page.
– Gateway AP will display the LAN IP address and let you specify the IP address.
– Repeater AP will leave the LAN IP section blank.
– The Repeater AP detail page also displays information about its route to the Gateway. This information is displayed on the RF tab.
3.Meraki Mesh Algorithm:
– Meraki devices in the mesh network communicate using a proprietary routing protocol designed by Meraki. This protocol is specifically designed for wireless mesh networks and for some of the unique characteristics of wireless networks (including variable link quality due to interference or multipath interference, as well as the performance impact of routed traffic). through many jumps).
– As part of the mesh’s self-healing capabilities, APs will automatically discover each other and choose the best route to the gateway. All mesh-enabled Cisco Meraki APs will automatically attempt to mesh if they lose their wired connection, or provide connectivity to the Repeater if it connects as a Gateway. Therefore, it is often recommended to allow automatic channel selection in networks with Repeaters.
– Each AP in the Meraki mesh network continuously updates its routing tables with optimal paths to network gateways. If the ideal path changes due to node failure or route metrics, traffic will go through another, more optimal path. Data traffic sent between devices in a Cisco Meraki network is encrypted using the Advanced Encryption Standard (AES) algorithm.
– In case the mesh gateway fails or a new mesh gateway appears with better routing metrics. All new traffic flows will be routed to the new mesh gateway.
4.How does the AP decide the mesh:
– When starting up the AP will always try to get an IP address over the wired interface. If the AP does not receive an IP address, the AP will switch to mesh mode and start searching for a gateway. The AP continues to request an IP address via DHCP on the wired interface even though the AP is in mesh mode. If the AP receives an IP address, it switches to gateway mode and starts transmitting mesh probes.
– Mesh probes: Each Meraki AP sends link probe packets (called mesh probes) at different bit rates and different sizes. Since these packets are sent as broadcast frames, there is no need for ACK frames from receiving stations. Four different types of probes at different data rates are sent in a series of 15 seconds on both frequency bands (2.4/5 GHz). All APs listen for mesh probes and depending on the number of mesh probes received correctly, give a link quality index as shown in the dashboard.
5.How AP chooses gateway:
– When the AP switches to mesh mode, the AP scans all channels to collect information from all neighbors. If a valid neighbor is found, it switches to that channel. The configured channel has higher priority if a valid neighbor is found on it. If no valid neighbors are found from all channels, it remains on the configured channel.
– Based on the scan results, the AP repeater creates a table of all detected gateways and their corresponding link quality metrics. In addition, the number of hops is also considered and priority is given to gateways with lower hops.
6.When does the repeater search for a new gateway:
– A repeater starts searching for an AP in two cases:
+ When a gateway is not working: If a gateway cannot be reached for 3 minutes, the gateway is marked as inactive. As soon as a gateway is marked as down, the AP begins scanning for new gateways. Will scan all channels (including 2.4 GHz and 5 GHz) and then choose the best one available based on the metrics. Higher priority is given to statically configured channels.
+ Repeater finds ports better: The repeater continuously evaluates the current channel it is operating on to find a better gateway, but each AP sends mesh information every 15 seconds. If the repeater finds an AP with a better link quality index of 1, the AP will switch to the new gateway.
– In most cases, when a repeater changes gateways, there are existing traffic flows that need to be considered and the repeater needs to ensure that the new gateway does not provide degraded performance. To ensure seamless data transfer and good user experience, the repeater does not switch traffic immediately. Current data flows use the old route for 5 seconds before being switched to the new route by the new gateway.
7. Impact of mesh on throughput:
– Due to the half-duplex nature of wireless communications and the signals transmitted through the AP repeater must be retransmitted to the next hop, throughput is significantly reduced when using a repeater. Although many factors affect wireless throughput, it can be assumed that the addition of mesh can reduce throughput by approximately 50%, with that reduction being applied to each subsequent repeater until reaching be gateway. Therefore, you should minimize the number of hops between the client and the gateway.
– Each AP repeater in the Cisco Meraki network transmits and receives the signal it receives from its AP (Wired) gateway so that other wireless APs (repeater) in the network can share the connection and extend the range. The Meraki Repeater uses a mesh algorithm to determine the best route between APs to an AP gateway that is physically connected to your LAN. Data traffic sent between devices in a Cisco Meraki network is encrypted using the Advanced Encryption Standard (AES) algorithm.
8. Monitoring Mesh :
– Monitoring Mesh tools are located at the bottom of each AP detail page, accessible by going to Wireless > Monitor > Access Pointsthen select AP.
– The image below shows an AP acting as a repeater. The time picker in the top right corner adjusts the time frame of all UI elements in the mesh monitoring section of the user interface.
– Mesh Routes : Routes Table shows the routes used by different threads over time. When new routes are selected, they are added to the routes table. The total amount of traffic per route during the selected time period is displayed in the Usage column. Metrics are also shown in this table, representing the combination of packet loss and delivery time. Average throughput Avg. Mbps is also provided to customers to evaluate the capacity of that particular mesh route.
– Mesh Neighbors: You can find the Mesh Neighbors table on the RF Tab on the AP detail page and displays the APs that have been automatically discovered. Link quality is a measure that takes into account signal strength and successful packet delivery rates in each direction. A link quality of 70% or higher is recommended for a strong link.
9. Disabling Mesh :
– Meraki allows disabling mesh on Meraki Access Points. The configuration toggle button is inside Network-wide > Configure > General > Device configuration.
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