Mesh Deployment Guide

Site survey

We recommend that you perform a radio site survey before installing the equipment. A site survey reveals characteristics such as interference, Fresnel zone, or logistics problems. A proper site survey involves temporarily setting up mesh links and taking measurements to determine whether your antenna calculations are accurate. Determine the correct location and antenna before drilling holes, routing cables, and mounting equipment.

Antenna selection

Selecting the appropriate external antenna for each access point in the mesh design is an important part of the design process. There are a number of external antenna options available from Cisco Meraki. In most cases, antennas with very narrow beam-widths are ideal for backhaul connections spanning long distances. The datasheet for the antenna will define the Half Power Beam-Width (HPBW) and the gains of the antenna. The information on the datasheet will help identify the best antenna for the application, however it is always recommended to have a Cisco Meraki Partner assist and verify the RF design of the mesh network. 

Maximize RF line of sight

A wireless signal travels most effectively through open space. As such, an AP with an omni-directional antenna should be positioned to maximize its line of sight both to wireless users and all needed coverage areas. "RF line of sight" is different than "visual line of sight" due to the way RF propagates though the air. 

Fresnel zones

A Fresnel zone is an imaginary ellipse encompassing the visual line of sight between the transmitter and receiver. As radio signals travel through free space to their intended target, they could encounter an obstruction in the Fresnel zone, degrading the signal. Best performance and range are attained when there is no obstruction of this Fresnel zone. Fresnel zone, free space loss, antenna gain, cable loss, data rate, link distance, transmitter power, receiver sensitivity, and other variables play a role in determining the throughput and reach of your mesh link goes. Functional links can still be made as long as 60% to 70% of the Fresnel zone is unobstructed, as illustrated in the figure below. A Cisco Meraki Partner can help assess a network design for appropriate clearance of the Fresnel zone.

Weather

In addition to free space path loss and line of sight, weather can also degrade a mesh link. Rain, snow, fog, and any high humidity condition can slightly obstruct or affect the line of sight, introducing a small loss (sometimes referred to as rain fade or fade margin), which can have a small effect on the mesh link. If you have established a stable mesh link, the weather should not be a problem; however, if the link is poor to begin with, bad weather can degrade performance or cause loss of link.

Ideally, you need a line of sight; a white-out snow storm does not allow a line of sight. Also, while storms may make the rain or snow itself appear to be the problem, many times it might be additional conditions caused by the adverse weather. For example, perhaps the antenna is on a mast pipe and the storm is blowing the mast pipe or antenna structure and that movement is causing the link to come and go, or there might be a large build-up of ice or snow on the antenna.

Point-to-point

In the point-to-point mesh scenario, one gateway access point provides access to one repeater access point. By default, the repeater access point will broadcast and serve all of the same SSIDs as the gateway access point. "AP tagging" may be used to disable specific SSIDs on the repeater. The repeater can extend an Ethernet segment from the gateway access point at the same time as providing wireless access to clients. Further discussion on Ethernet bridging is found below. 

Applications for which this deployment scenario is appropriate include:

• Bridge link between a main office and a remote temporary office

• Extend the reach of infrastructure-based wireless network at a campus to less critical, hard-to-reach areas like sports fields or parking lots

• Extend a secure network from an industrial core to a non-mission-critical or temporary roadhouse or satellite building 

Point to multi-point / Multi-point to multi-point

In the point to multi-point scenario, one or more gateways serve multiple repeaters. All gateways and repeaters may broadcast the same SSIDs and serve wireless clients.

Applications that these deployment scenarios are appropriate for include:

• Provide backhaul for multiple temporary buildings

• Reach remote wireless access point clusters

• Cover low bandwidth subscribers over a large area

Wireless client handling on a repeater

VLANs and other SSID settings like firewall and traffic shaping settings will be maintained on SSIDs that are served by repeater access points. 

Gateway-to-repeater ratio 

In general, it is desirable to have as many gateway access points as possible to maximize overall network performance and reliability. As a general guideline, it is recommended to plan for no more than two repeater access points attached to each gateway access point.

Maximum mesh hops 

There will be a throughput reduction (~50% reduction) with each “hop” in a mesh. It is recommended that a mesh network be designed for no more than one mesh hop from the gateway to client device.

Multi-path mesh 

In order to ensure that there are multiple failover paths, it is recommended that each mesh access point has at least three strong “neighbors”, or other access points in the mesh that the access point can “see”. The Mesh Documentation gives an overview of the different monitoring tools available on the Meraki Dashboard, including an overview of the Neighbors Table. 

Ethernet bridging

The gateway access point may be configured to connect to a trunk port and trunk SSIDs to different VLANs. Repeaters will also serve SSIDs trunked on different VLANs. However, only one SSID & associated VLAN may be configured to bridge wired clients across a mesh link on a repeater access point's Ethernet port. A mixture of wired clients and Cisco Meraki access points attached to one MR repeater interface is not a supported deployment configuration. This is due to the auto detection mechanisms that Cisco Meraki access points use to infer when they should function as a gateway or a repeater.

Mesh wired access may be treated like a traditional point-to-point link with a router on the remote site. Access points may connected to a repeater with a Layer 3 router separating the broadcast domains. For further discussion on this design, see Extending the LAN with a Wireless Mesh Link documentation article.