I am trying to implement server auto discovery so that clients will be able to see a list of servers available to connect to. I would like to auto discover servers even if they are in different subnets.
I have read that windows does not respond to broadcast ping, but is it possible to make all these servers to join a multicast group and use multicast ping on the group to see what servers are up?
Thanks
Try Zero configuration networking (Zeroconf).
Note multiple LAN segments requires routers to be configured to route multicast traffic, they do not by default. Similarly IGMP enabled switches are usually recommended for computer connectivity.
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I have 2 EC2 instances (one window and one linux) in same subnet. I am trying to access one instance from another via private IP but I am not able to do so.
In security groups, both instances belong to same security groups and security group allows all traffic from the same security group.
I am not even able to ping one instance from another using private IP address.
Any pointers what could be wrong here.
By default the Windows firewall will deny all inbound requests (including ping), but the firewall also contains a list of Exceptions (otherwise it would block everything!). Those Exceptions are a set of rules that describe what connections should be allowed in out-of-the-box.
To allow any additional connections, you just add a new rule to the firewall. There is a Wizard in the Windows Firewall GUI for viewing and creating rules, but i find it easier to use a PowerShell one-liner like this to allow ping:
New-NetFirewallRule -DisplayName "Inbound LAN Ping" -Direction Inbound -Protocol ICMPv4 -IcmpType 8 -RemoteAddress 192.168.1.0/24 -Action Allow
Above will allow any IP's between 192.198.1.1 ... 192.168.1.255 to send ping requests to your Windows host (all other RemoteAddress will still be ignored). I'm assuming here your Linux machine's IP is for example 192.168.1.1 and your Windows machine's IP is 192.168.1.123.
As a rule of thumb, you should only open up the minimal number of ports, to as few IP/IP ranges as possible.
This will likely be the result of Windows firewall being enabled, with default settings it will block ping access (among other things).
Disabling it should enable inbound/outbound access to work for ping. This is a temporary measure and should not be considered a permanent workaround.
You should enable whitelisting in the Windows firewall to allow the ports you would like inbound or outbound to have network access to/from other resources within the network.
More information is available in this link.
Good day
Do you have any idea how to find WIFI routers or devices which is connected to specific LAN sockets in network?
I am try find this devices from logs Elasticsearch + Kibana namely
https://www.elastic.co/guide/en/beats/packetbeat/current/configuration-interfaces.html
With this solution I have problem with set up : packetsbeats.
Other solution which I found is : WireShark or Advanced IP Scanner or Angry IP.
With this solution /tools is problem with default setting of routers / devices which is lock ports. Its mean I can get all IPs or MACs in network but how I will get know which is IPs or MACs belonging to Routers / NTB / Mobiles ect..?
From this reason I decide find routers in network from logs by Kibana.
Do have any idea or did you make something like me?
Thanks
Wi-Fi (IEEE 802.11) is a layer-1/2 protocol, but routing is a layer-3 function, so there really is no such thing as a Wi-Fi router. There are some routers that have Wi-Fi interfaces, but they are routing a layer-3 protocol, e.g. IPv4, not Wi-Fi. Ports are layer-4 addresses for some layer-4 protocols, e.g. UDP, and they have nothing to do with routing layer-3 packets.
A router is simply a host on a layer-2 LAN. The configured gateway for your host is usually a router. The gateway is the host on a LAN to which your host sends packets destined to a different network.
Determining which hosts on a LAN are routers is a problem because you have no way to know which hosts are actually routers. You can have multiple routers on a LAN, but your host will be configured with one as its default gateway.
If you want to determine which host is the gateway for your host, then you should look at the configuration of your host, not at any particular host on the LAN.
I am splitting an application into a tray application and a Windows Service and I want to use TCP to communicate between the two*. They will both be running on the same machine.
My question is do firewalls block TCP communication between applications running on the same machine? I want to know whether firewalls are something I need to worry about when testing.
(*note that I want to use TCP instead of named pipes for communication because the apps might one day run on separate computers but that will be far in the future)
The primary objective of the firewall is to control the incoming and the outgoing network traffic! Firewall's are designed to work on IP or PORT basis.
So yes, it is 100% capable of blocking connection on same machine.(I guess you are using Class A IP [127.x.y.x] address used mainly for loopback testing and interprocess communication on the local computer).
Some firewall are preconfigured not to block local machine connection while other are configured to block them. But either way a firewall can be configured to allow/deny such connection.
On my computer, when I try to ping to a multicast address, none of them return a response.
On the other hand, there is a Unix server I know that does have ping to these addresses.
Is there a way to add a route from my computer to this one, so that I can use these addresses?
No, ICMP is not typically used with multicast because it is a prime source for DoS amplification. Similarly multicast doesn't tend to be that useful as you need multicast enabled and configured routers to cross LAN segments.
See this answer if you are wanting to use multicast pings for discovery of local machines:
Multicast Ping (Windows)
I'd like to sell headless Linux servers to SOHO users. Typically, they'll have a DHCP-capable ADSL modem cum switch to which they'll connect their workstation and the server.
In order to just show up with the server, I need to find a way to just plug the server into the switch to get an IP address from the modem, and then have the server broadcast its adresse so I can then connect to it with Putty from the workstation.
I thought about using Samba to broadcast a message using the Messenger Service, but unless I'm mistaken, this only works if the two hots are configured to use the same workgroup/domain.
Do you know of way to get the server's IP address from the workstation?
Thank you for any tip.
Take a look at UPnP and zeroconf services like Apple's Bonjour.
I'd probably suggest using the normal approach for switches and modems as you are treating your device as an appliance, i.e. set a default IP 192.168.0.1, and connect to that to then configure the device into the local infrastructure.
I don't know of any good solutions.
Some DHCP servers will register the name you send in the request - then give that name in your setup instructions. But I suspect home user DSL routers aren't in that category.
Maybe you could ship a tool on CD that does arp requests to get the IP address? (Given the MAC address printed on the box)
Broadcast packets periodically on some arbitrarily chosen UDP port, and build some client software to listen for those packets.