Local servers — which IP do devices point at?

What it does: the Local servers tool stands up test servers on THIS machine (Syslog, SNMP-trap, TFTP, HTTP, FTP, DNS, DHCP, RADIUS, TACACS+) so your gear can point at your computer instead of a real appliance.

Which IP do I give the device? Use THIS computer's IP address on the network the device can reach — normally your Ethernet or Wi-Fi adapter's LAN address (for example 192.168.1.50 or 10.0.0.5). You can see it on Home under "This machine", or with ipconfig (Windows) / ip addr (Linux). You do NOT choose an IP in the app: a running server listens on ALL of this machine's addresses at once, so you just tell the DEVICE which of them to use.

Do I need a management loopback or VLAN? No — not on this host. A loopback / management VLAN is a DEVICE-side idea: a router can use its Loopback0 as the stable SOURCE address for the syslog/SNMP it SENDS. That's configured on the device, not here. The machine running these servers just needs an IP on a network the device can route to.

The recipe: (1) the device and this machine can reach each other (same subnet, or routed between them); (2) on the device, set the destination — logging host / trap host / tftp server / dhcp helper, etc. — to this machine's IP and the PORT shown on the server's card; (3) allow it through the firewall (Windows prompts the first time you Start a server — choose Allow on Private networks).

Ports: the defaults ARE the real service ports — syslog udp/514, SNMP-trap udp/162, TFTP udp/69, DNS udp/53, DHCP udp/67, RADIUS udp/1812, TACACS+ tcp/49, FTP tcp/21 — because that is what network gear sends to. Most of these are not negotiable: TFTP, DNS, DHCP, FTP, RADIUS and TACACS+ are fixed by protocol, and IOS 'ip name-server' has no port option at all. Only syslog and SNMP-trap let a device choose a different destination port.

You can still edit any port here — do that when your shop runs a collector on a non-standard port, so SubnetSlinger matches your environment. What you should NOT plan on is repointing production gear at a high port to suit this app: changing a live device's logging or trap destination is a change against production config. Moving to a high port is only realistic for equipment you control — a lab, a bench, a staging rack, a site you're still building.

Do you need admin? It depends on the OS, and this is worth learning properly. Ports below 1024 are 'privileged'. On macOS and Linux a normal user cannot bind them at all — that is a hard kernel rule. On WINDOWS there is no such restriction: SubnetSlinger binds udp/514, tcp/49, udp/53 and the rest as a standard user with no elevation. What Windows does require is a firewall rule to let the traffic IN — binding and receiving are two different permissions, and confusing them is a classic source of 'the server is running but nothing arrives'.

Multiple adapters: if this machine has Wi-Fi + Ethernet + a VPN, the device must use whichever of the machine's IPs is on ITS path. Since the servers bind every interface, any of them works — just give the device the right one.

Security: while a server is running, anyone on that network can reach it, and these are lab tools with minimal or no authentication. Only run them on a trusted network, and Stop them when you're done.