C / C ++ Linux，如何在网络上查找邻居不使用IP（仅MAC） [英] C/C++ Linux, How to find neighbors on a network Without Using IP (MAC Only)

问题描述

在一个小型网络中，说20个节点或更少，我的程序，在测试仪器上，需要知道谁在那里？由MAC而不是IP。我将插入随机网络，需要能够做到这一点，而不必知道任何地址，MAC或网络中的其他，知道我不能依赖DHCP。完全合理的DHCP服务器可能关闭，节点没有IP地址和/或，我不能得到一个。实际上，我不需要IP，我们的测试协议是MAC层，而不是IP。

In a small network, say 20 nodes or less, my program, on a test instrument, needs to know "Who is out there?" by MAC not by IP. I will be plugging into random networks and need to be able to do this without having to know any addresses, MAC or otherwise in the network and knowing I can't rely on DHCP. It is completely reasonable that the DHCP server could be down and the nodes have no IP addresses and/or, I can't get one. Truthfully, I don't need IP, our test protocol is MAC layer, not IP.

那么，如何确定我的仪器的邻居的MAC地址？这听起来很像LLDP，但是向后，即谁在那里，而不是我在这里，我可以做到这一点...。我必须假设没有IP分配到端点，所以没有ARPing，没有NMAP等。

So, how can I determine my instrument's neighbor's MAC addresses? This sounds a lot like LLDP but backwards, i.e., "who's out there", not "I'm here and I can do this...". I must assume there is no IP assigned to the endpoints, so no ARPing, no NMAP, etc.

注意我应该添加，这是有线网络。

Note I should add, this is a wired network.

推荐答案

在一般情况下，没有可以发送的MAC级别协议，并保证网络上每台机器的响应（我假设你在这里使用以太网，因为我相信在WLAN上的东西不同）。 IE在主机保证响应的MAC层没有广播（或甚至，IIRC单播）。在IP上面，你可以IP广播和检查ARP缓存。

In the general case, there is no MAC level protocol that you can send and guarantee a response from every machine on your network (I am assuming you are using ethernet here as I believe things are different on WLAN). IE there is no broadcast (or even, IIRC unicast) at the MAC layer that a host is guaranteed to respond to. With IP on top, you can IP broadcast and check the ARP cache.

最好的方法是（我认为）是使用开关/学习网桥工作在以太网，即被动地以混杂模式监听数据包并记录其MAC地址。你不会发现完全沉默的主机，但两者都不会切换，直到它发送一个数据包。根据定义，没有办法找到一个完全沉默的主机。

The best way to do this would (in my opinion) be to use the way switches / learning bridges work on ethernet, i.e. passively listen in promiscuous mode for packets and note their MAC addresses. You won't spot completely silent hosts, but neither will a switch until a packet is sent by it. By definition there is no way to spot a completely silent host anyway.

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