Build the network map from your switches on iPhone

A device list tells you who is on the network. A map tells you where they are plugged in. NetBlade builds the map from the same scan, adding structure read from managed switches over SNMP, and lets you correct whatever the switches cannot prove. This article shows what the switches need, how to build the map and how to fix it by hand.

Before you start

• A saved network with SNMP working on the router, so devices have MAC addresses. See Get MACs and vendors from your router over SNMP.
• For a real tree: one or more managed switches with a management IP address in the subnet you scan, and SNMP enabled on them.
• The map and SNMP are free on iPhone.

Note: On a home network with no managed switch, the map is a star around the router. That is the honest picture of a single segment, not a broken map.

1. Understand how the map is built

NetBlade works in three layers, each overriding the one before:

1. The star. Every device hangs off the gateway. Always true enough to draw.
2. The reconstruction from SNMP. LLDP tells NetBlade which switch is connected to which, building the backbone. The switches’ bridge forwarding tables, the list of which MAC address each port has learned, place every device under the port it is plugged into.
3. Your corrections. Whatever you set by hand wins over both, and is kept for that network.

This is why MAC addresses matter: a device is placed by matching its MAC in a switch’s table. A device without a MAC cannot be placed.

2. Prepare the switches

On each managed switch, in its admin page:

1. Give it a management IP address in the same subnet as the phone, so the scan finds it.
2. Enable SNMP with a read-only community or a read-only v3 user (SHA or MD5 for authentication, AES or DES for privacy).
3. If the switch supports LLDP, enable it. It lets NetBlade see switch-to-switch links directly.

If the switches use the same SNMP credentials as the router, you have nothing else to do in NetBlade. If a switch uses different ones:

1. Tap the switch in the LAN list to open its details.
2. Open «Credentials (this device)» and enter its SNMP credentials.

The map uses each device’s own credentials where it has them, and the network’s where it does not.

Tip: Unmanaged switches, the ones without an admin page, have no IP address and do not speak SNMP, so no tool can see them. The devices behind one appear under the managed switch or router it is plugged into. Access points with an IP can be promoted by hand, as shown in step 4.

3. Build the map

1. Scan the network from the LAN tab.
2. In the «List» / «Map» picker choose «Map».
3. Wait while NetBlade queries the devices over SNMP; a spinner shows at the top right.
4. Tap «Rebuild» whenever you want to redo the structure. It re-runs only the SNMP pass, not the whole scan.

Two views are available with the toggle at the top: a graph and an indented tree. The tree is easier to read on large networks; tap a row’s arrow to collapse a branch.

4. Correct it by hand

Tap any node. A panel opens with the device’s name, address and kind, and these actions:

• «Open details»: go to the device’s page.
• «Mark as switch» or «Not a switch»: tell NetBlade whether this device is a piece of infrastructure other devices can hang off. Use it for an access point, an unmanaged switch that has an IP, or a device NetBlade guessed wrong.
• «Connect to…»: choose which switch or gateway this device is plugged into.
• «Detach»: remove your manual link and let NetBlade decide again.

Corrections are stored per device and per network, so they survive the next scan and the next «Rebuild».

Note: The gateway and this iPhone cannot be edited, and a device without a MAC shows “MAC unavailable — this device can’t be placed on the map.”

Check that it worked

• Under each managed switch you see the devices plugged into it rather than everything hanging off the router.
• The message “No managed switch answered SNMP — this network is a single segment” is gone.
• Opening a switch’s details, «Query device over SNMP» shows its interfaces and VLANs: tap an interface for live traffic.

If something goes wrong

• Still a star, and the message about a single segment. No switch answered SNMP. Check that the switch appears in the LAN list at all, that SNMP is enabled, and that the credentials match. Test it with Tools › SNMP.
• The switch answers but devices are not placed under it. Those devices probably have no MAC in NetBlade. Fix the router SNMP first.
• Some devices appear under the wrong switch. Forwarding tables change as devices go quiet. Use «Connect to…» to fix them; your choice is kept.
• A second switch hangs off the router instead of the first switch. Without LLDP, NetBlade may not see the link between switches. Enable LLDP on both, or connect it by hand.
• Changes on the network did not update the map. Tap «Rebuild».

Next

• Inventory Windows and Linux PCs
• SSH terminal, SFTP and FTPS
• NetBlade guide for iPhone and iPad: network map

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