Wired devices not talking to devices past the switch

[pentax9380]

OK, here's the deal. I've set up my network at my parents place thusly. I'm running a Buffalo WZR-HP-G300NH router using DD-WRT v24-sp2 (06/23/14) std. The Comcrap modem is plugged into the WAN port. I have my mothers PC (MOMPC) plugged into port 4 on the router. I have a line running from Port 1 on the router to Port 1 on a TrendNet TEG-S5g 5 port Gigabit switch. My server, LARGO, is plugged into Port 2 on the TEG-S5g, my MyCloud EX4 is plugged into Port 3, and a line runs from Port 5 to Port 1 on an 8 port TEG-S80g switch in my bedroom. My Roku is plugged into Port 2 and my PC is plugged into Port 3 of the TEG-S80g. Here's the problem. Everything wireless can talk to LARGO and the MyCloud without issue. Any PCs plugged into the router via wire cannot talk to LARGO or the MyCloud, pinging gets a "Destination host unreachable" error. Anything wired plugged into either switch talks to the server fine. Anything wired connected to the router can talk to each other fine. I'm not a moron when it comes to networking but this has me stumped. Any help?

 

[bill001g]

Very complex but if I read correctly the only thing that does not work is devices plugged directly into the router lan ports talking to devices plugged into one or more of the other switches. If you move these PC down to one of the other switches they work fine ?

There really shouldn't be any difference between the lan ports in the router and the other switches. This is actually a small switch on a single chip built into that router. Just out of desperation I am going to blame dd-wrt since it has many options to configure this switch and it may be doing something strange. Be very sure you do not have any duplicate IP addresses assigned.

There are only a couple ways this can't work, all traffic is via mac address when you run with switches. I really have no good answer for you but a few thing you can check.

So on each device issue the ping command for the other machine and it should not work but it should create arp entries. What you want to do is quickly issue arp -a. Now if you actually see a mac address associated with the ip (make sure the mac is correct) it means the other end answered.

If you see the mac address as zeros and invalid this means it did not get a response. Something may be blocking the ARP commands. If you see mac addresses on both ends and they are both valid then it becomes even more strange because that means it will let arp pass but not any other traffic. This is common when there is a firewall in the path.

You could try putting in a static arp entry using the arp -s command if you can not get a response but this is almost crazy to try when it should just work.

This is almost acting like you have vlans defined in the dd-wrt router but then you would think the lan ports would not talk to anyone.

It should just work so I am pretty stumped too.

 

[pentax9380]

Thanks bill001g, you gave me the clue I needed. Turns out there's a bug in DDWRT that enables a VLAN, screwing up the ARP for devices on switches. The solution is described on the DD-WRT Wiki entry for my router:

http://www.dd-wrt.com/wiki/index.php/Buffalo_WZR-HP-G300NH

I ran the commands to disable the VLAN, and viola, all is right with the world. Thanks for the clue!!