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I am connected to Internet with just one Linux home PC: a laptop. My ISP's router is a combo modem and router in one box. The brand is Technicolor TC 7200.

I ran this command # arp-scan --localnet and the output was:

# arp-scan --localnet
Interface: eth0, datalink type: EN10MB (Ethernet)
Starting arp-scan 1.9 with 256 hosts (http://www.nta-monitor.com/tools/arp-scan/)
192.168.0.1     xxxxxxxxxxxxxxxxx   Technicolor USA Inc.
192.168.0.10    xxxxxxxxxxxxxxxxx   Thomson Inc.

I know that 192.168.0.1 is the private IP of the router (gateway) but what about 192.168.0.10?

Is 192.168.0.10 the private IP of the modem in the combo device or this is some other device?

Does the modem has its own private IP?

Does the modem have ports on their firmware like the ports of the PC's OS?

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  • Are you simply trying to understand something you find confusing, or are you concerned about something like a possible security issue? Your comments under my reply seem to indicate there's questions BEHIND this question you've posed. We don't really do well with that, because you've asked us to expend effort answering something but you haven't give us all the information. Please make sure you are asking the actual question, so that we can do our best to make sure to get you the answer you actually want to receive.
    – music2myear
    Commented Dec 10 at 14:09

3 Answers 3

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Different devices do things differently, but yes. Your device has one public internet facing IP.

Everything else internal, and is private and has its own IPs.

Generally with the 192.168.x.x prefix. All IPs have ports and you can map the external to the internal with port forwarding.

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192.168.10 is not an IP address. All IPv4 addresses have 4 "octets", or sections. Your copy/pasta shows 192.168.0.10, I edited your post to correct that issue.

Every device on your network has an IP address. However, all you can "see" on your network will be the things downstream from the Router, the Technicolor device. The Modem exists upstream from the router. It almost definitely has its own IP address, and they modem and router components of that device may even have their own private network between themselves, over which all the traffic from your LAN headed out to the internet, and all the traffic from the internet headed into your LAN, will pass. But that depends on the configuration of the device.

What you're seeing is another device on your LAN, your (L)ocal (A)rea (N)etwork which has that IP address and identifies itself as "thomson". Further proof of this is that the IP address assigned to that device, being in the same subnet, has a higher number.

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  • But ... on my LAN I have just my laptop - 192.168.0.1x and my router 192.168.0.1!!! And from time to time my Android-phone. Nothing else! What is going on here!? My ISP has packed me with someone else!?
    – ccsann
    Commented Dec 10 at 7:38
  • And about 20 days ago I noticed that my public IP does not change.
    – ccsann
    Commented Dec 10 at 7:46
  • I already answered that: You are seeing things INSIDE your LAN. If there's a wireless network, there may be a wireless device you've forgotten about, or you have a simple wifi password and someone else has connected. You've already told us your other IPs, and those are all private IPs that won't help anyone "hack" you, so there's no reason to conceal those IP addresses. Your "public IP" is set whenever your modem reconnects or resets, or if your ISP decides to change it. It being the same for 20 days is normal.
    – music2myear
    Commented Dec 10 at 14:08
  • Your reviewed and rejected my edit, but did you actually mean copy/pasta?
    – Dong Li
    Commented Dec 11 at 16:14
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    Yes, I did. It means the same thing, it's colloquial and a little light-hearted.
    – music2myear
    Commented Dec 11 at 16:43
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Does the modem has its own private IP?

No, generally not. With an integrated unit, although the 'modem' and 'router' are conceptually separate, the router's firmware usually controls the modem by other means – not as a separate network device but as an internally connected chip (or, at most, as a USB device as is the case with many 4G/LTE modems).

(And even if it did, like when the router is a physically separate unit from the modem, it would still be on the other side of the router anyway – where ARP queries from your LAN wouldn't be able to reach it.)

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  • I made nmap -A for 192.168.0.10 and posted the output like my answer but DavidPostill hided it. Here are some parts from the output: 23/tcp open telnet security DVR telnetd (many brands) 80/tcp open http BusyBox httpd 1.13 |_http-title: Site doesn't have a title (text/html). 111/tcp open rpcbind 2 (RPC #100000) | rpcinfo: | program version port/proto service | 100000 2 111/tcp rpcbind |_ 100000 2 111/udp rpcbind 139/tcp open netbios-ssn Samba smbd 3.X - 4.X (workgroup: WORKGROUP) 445/tcp open netbios-ssn Samba smd
    – ccsann
    Commented Dec 11 at 14:42
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    You made an answer to your post which was not an answer. DavidPostill did the correct thing deleting that. If you have further information to add to this question, it needs to be added to the main question using the EDIT button. With the multiple missteps you've had regarding this, I strongly recommend that you review the Help section, and that you read all the suggestions Superuser presents you as you're posting questions. These are intended to help you understand how this works.
    – music2myear
    Commented Dec 11 at 23:50

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