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My computer is connected to my secondary router that's running the 192.168.42.0/24 network and my computer also has a route that directs anything on that network to the router, but for anything on that network other than the router itself, it get's the ICMP response of Reply from 192.168.42.194: Destination host unreachable. (with 192.168.42.194 being my computer). Every other network works, like all of the internet, or addresses on my primary router like 192.168.1.*, just not on the 192.168.42.0/24 network...

route print returns:

IPv4 Route Table
===========================================================================
Active Routes:
Network Destination        Netmask          Gateway       Interface  Metric
          0.0.0.0          0.0.0.0     192.168.42.1   192.168.42.194    276
        127.0.0.0        255.0.0.0         On-link         127.0.0.1    306
        127.0.0.1  255.255.255.255         On-link         127.0.0.1    306
  127.255.255.255  255.255.255.255         On-link         127.0.0.1    306
     192.168.42.0    255.255.255.0         On-link    192.168.42.194    276
   192.168.42.194  255.255.255.255         On-link    192.168.42.194    276
   192.168.42.255  255.255.255.255         On-link    192.168.42.194    276
        224.0.0.0        240.0.0.0         On-link         127.0.0.1    306
        224.0.0.0        240.0.0.0         On-link    192.168.42.194    276
  255.255.255.255  255.255.255.255         On-link         127.0.0.1    306
  255.255.255.255  255.255.255.255         On-link    192.168.42.194    276
===========================================================================
Persistent Routes:
  Network Address          Netmask  Gateway Address  Metric
          0.0.0.0          0.0.0.0     192.168.42.1  Default
===========================================================================

The only time anything is supposed to send an ICMP Host Unreachable response is when there's no route to it, right? So, why is my own computer sending that to ping or tracert when I have the route of 192.168.42.0 with the mask of 255.255.255.0? An IP address of 192.168.42.2 surely fits into that route. If I explicitly add a route for the IP address i am trying to access, it works, like: route add 192.168.42.2 mask 255.255.255.255 192.168.42.1 (the 192.168.42.1 right after mask is gateway, or the device to send the packet to so it can route it further), but why wont it work for the implicit route that's automatically on the table? I disabled my firewall, too (I use Comodo if anyone thinks this still serves as a problem). I'v even tried explicitly adding the gateway of 192.168.42.1 to the 192.168.42.0/24 route instead of it routing through 0.0.0.0's gateway, which is what On-link does. but that didn't work either, so it's not a gateway specification problem.

If the host was really unreachable, it would be the router's IP address (192.168.42.1) sending that to me...

This network is all of my creation, so there's no problem such as an administrator locking me out, because i am the administrator.

EDIT
In this case, the secondary router is hosting a VPN, ARP will not work because of this. My own answer will be posted below because of this realization. (well, i just figured out i can't post my answer until the duplicate question flag is removed... the answer to the question it is marked duplicate does not explain how or why windows ignores routes in some cases, which, especially shown by title, shows it is not the same question...)

GigabyteProductions
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  • I doubt this question will be reopened. Questions about equipment in a home setting are off topic here. – MDMarra Nov 10 '13 at 05:04
  • Well stackexchange only titles it as "Q&A for professional system and network administrators", this is network administration... i don't see how server configuration and network configuration doesn't go with network administration. – GigabyteProductions Nov 10 '13 at 05:09
  • You missed the key word "professional". I agree that this wasn't a duplicate of the other question, though. – Michael Hampton Nov 10 '13 at 05:22
  • If this can't fit into any professional networking administration, which stackexchange website should i have been going to? I was researching this problem for a few days before i decided to come to a Q&A or forum of any kind, it really doesn't help when i can't get an answer from anyone here. I'm just letting you know that so i don't make myself look like one of the bad users of the website. – GigabyteProductions Nov 10 '13 at 05:36
  • Superuser.com - the fallback for all non professional questions. – TomTom Nov 10 '13 at 07:55
  • You've got an issue at layer 2. Your computer can't ARP for machines on the same broadcast domain. That's why adding a static route works. When you add the static route, you ARP the gateway successfully and the gateway can ARP the destination for you. To work correctly the ARP should be peer to peer. The router interface your computer is connected to is probably providing a layer 3 boundary (routed) rather than just a layer 2 segment (switched). – Ryan Nov 12 '13 at 21:05
  • Yeah i figured out that it was ARP and was in the middle of typing the solution as i got the popup saying it was closed... Since i wasn't on the vpn and my computer expected to have the mac address to one of the other hosts because it was in my subnet, it said it was unreachable... I changed my subnet mask to 255.255.255.255 and added a route that sent 192.168.42.0/24 to 192.168.42.1 (i am directly connected to 192.168.42.1) and let the linux router route it from there... is there a way to set something like a NOARP flag on an interface in windows like in linux? – GigabyteProductions Nov 28 '13 at 03:43

1 Answers1

4

  1. Trying to route traffic for any ip address on the same subnet to your router is incorrect. Traffic to/from those computers doesn't need to be routed and won't be routed by the router.

  2. Pinging ip addresses in your subnet will only work if there are active computers with those ip addresses on the network.

  3. You're misinterpreting the ping response. For local ip addresses a Destination Host Unreachable response means that the computer you are trying to ping TO is not responding to the ARP request from the computer that you're pinging FROM. The ip address you're pinging has to be resolved to a MAC address and if your computer gets no response to the ARP request for the MAC address from the destination computer then you'll get Destination Host Unreachable.

EDIT

Have a look at this diagram. You'll notice that all of the hosts on the left are in the same network (130.103.1.x) and that all of the hosts on the right are in the same network (130.103.2.x) . You'll notice that the two networks are different from each other. Communication between the hosts on the left stays on the left. Communication between hosts on the right stays on the right. In neither case does the traffic cross the router. Only when a host on the left network needs to communicate with a host on the right network does the traffic cross the router. When traffic crosses the router it IS being routed. When traffic does not cross the router it IS NOT being routed. (Image courtesy of http://www.dummies.com/how-to/content/exploring-tcpip-routers.html)

enter image description here

joeqwerty
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  • For 1: that is what a router is for, the two computers aren't connected directly to each other, they are both connected to a central router, a router has it's own routes, where it sends the packers, that's why it's a router, it sends packets to their corresponding routes. For 2. There is a computer on the other ip address For 3: what? everything works fine, except for MY COMPUTER, the router can ping both computers, just my computer can't ping out on 192.168.42.0/24. – GigabyteProductions Nov 10 '13 at 03:25
  • How are they connected to the central router? Computers in the same subnet do not need their traffic routed. If you have two computers connected to two different interfaces on the router and if those computers use ip addresses in the same subnet then they will never be able to communicate with each other. Routers route traffic from one network to another network. Routers do not route traffic from one computer to another computer on the same network. – joeqwerty Nov 10 '13 at 03:27
  • Routers route all traffic that goes through, routing from 1 computer to another on the same network happens everywhere, haven't you heard of LAN? – GigabyteProductions Nov 10 '13 at 03:32
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    Routers DO NOT route traffic for communication between hosts in the same network, plain and simple. – joeqwerty Nov 10 '13 at 03:35
  • So you tell me then, how do you communicate with a device in your network, if the router that everything is connected to and everything physically has to go through doesn't route that traffic what does? – GigabyteProductions Nov 10 '13 at 03:40
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    It is being SWITCHED. It is not being ROUTED. It sounds like your router also has a built in switch. If so, then when hosts connected to the router communicate with each other the router SWITCHES the traffic. How about telling us what Make/Model router you have and tell us which ports your computers are plugged in to? Also, can you post a diagram? – joeqwerty Nov 10 '13 at 03:45
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    Now it could be that you have a router with multiple ROUTED interfaces and it is not a switch at all. If that's the case then there's no way to make a router route traffic from one network to another network if both networks use the same network address space. If your router has multiple ROUTED interfaces and you're trying to use it to connect computers that are in the same network address space it will not work. In that case you need a switch. – joeqwerty Nov 10 '13 at 03:49
  • Yes, my routers both act as switches, i have other hosts on them that can ping each other just fine, it's just in my scenario on my computer that isn't doing it, i am able to get a full connection when i add that explicit route to the specific IP address i am trying to access, remember that, but why isn't it letting me with the routes that are listed? Doesn't the traffic have to cross the router if they are all connected to it? even if their destination isn't the other side, it has to cross the router to get from 1 interface to another on the router. – GigabyteProductions Nov 10 '13 at 04:08
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    It crosses from one interface to another but not by being routed. The traffic is being SWITCHED from one interface to the other. You do not need to add routes for hosts on the same network. – joeqwerty Nov 10 '13 at 04:40