Why does traceroute show a direct connection to my home network devices instead of going via the router?

Question

I have 2 laptops connected to my home router, with the IP addresses 192.168.1.10 and 192.168.1.11.

I use traceroute 192.168.1.11 from the first laptop and I get

1    22 ms    11 ms    33 ms  Laptop2 [192.168.1.11]

I expected it to first go to the router, and then to Laptop2, but it directly showed Laptop 2.

The ARP tables were flushed before this command, and they did not list Laptop 2.

Answer 1

Traceroute does not show you every hop in your network, but rather only shows you how many layer 3 hops are being made.

A simpler way to understand it is that any network device that does not decrement the TTL will not show up in a traceroute as this answer on the Network Engineering Stack Exchange site explains:

Any device, that does not decrement IP TTL field value is not going to show up in the traceroute path. For example, Cisco ASA Firewall can be configured to decrement the IP TTL field for packets traversing the firewall (set connection decrement-ttl). By default, the TTL is not being decremented, thus hiding (well, somewhat) the firewall.

More insight can be gleaned here on this DSLReports page titled, “Should I use Layer-3 switch or router?”:

In general, you want to use a router when most of the time the device does routing. Likewise, you want to use a switch when when most of the time the device does switching. This statement becomes more apparent when dealing with larger network like an ISP or large corporation.

As well as this discussion on Reddit titled “Router vs Layer 3 Switch: What's the difference?” and specifically this answer from “Xipher”:

It's not really a functional difference. To me it's based on primary purpose.

An L3 switch routes, but usually with a much smaller routing table, and can only support a single a single set of VLANs. It's functionality will probably be pretty limited as well. Some switches are supporting a limited set of MPLS features, but that's mostly in the data center space.

A router can usually support a lot more routes. Most handle about a million or more IPv4 routes for current routers. Some will support switching, and even support overlapping VLAN space for the purpose of carrying customers L2 tunnels. Additional features like MPLS applications are also more common with routers.