The following setup:

  • Two linux hosts s=server, c=client
  • One switch which is fully VLAN capable
  • Tagged port setting and tagging enabled on the server/switch side
  • Untagged everything on the client side
  • One IP network
  • This, no layer 3/ routing is used
  • Firewalls are disabled on both ends
  • Routes look good on the server

I can:

  • Arp Ping the server from the client
  • Ping from the server outwards s --> *
  • Reach the Internet via a router in the client network

I cannot (my problem):

  • Ping or connect to any service from c --> s

What am I missing, shouldn't this work?

Update #1

I fixed it, although the firewall (shorewall in this case) was stopped, I found the following iptables rules which seemed suspicious to me:

$ iptables --list-rules

Changed them to ACCEPT, makes it work. Now I try to find out where those rules came from.

Update #2 I could not find out where these rules were coming from. I ended up doing iptabled --flush and iptables-save and now the rules seems to be reset also across reboots.

  • If you have one IP network, what routes are configured on the server that look good? Does the client need analogous routes configured on it? Do the client and server both have a 192.168.178.x address? And are they both connecting to the same VLAN? Mar 24, 2015 at 20:34
  • They only have a default route to some gateway in the same network and of course through the right ethx.x interface. An yes, all hosts are in the same network.
    – vanthome
    Mar 25, 2015 at 6:38

1 Answer 1


Run a traceroute from C to S and again from S to C. Compare the results, they should be the same, just reversed. Sounds like your packets may be taking a different route from C to S versus S to C.

Also, check the Windows firewall service on both ends...

  • 1
    check the Windows firewall service on both ends - 1. The OP stated that these are Linux hosts. 2. The OP also stated that the firewalls are disabled. 3. Check the firewalls for what specifically?
    – joeqwerty
    Mar 24, 2015 at 20:10
  • 5
    @joeqwerty I agree with Davan on this. If vanthome is running the Windows Firewall on his Linux hosts, that's a serious problem. :p Mar 24, 2015 at 20:35
  • Very funny, guys. ;) Sorry I missed that. Just waiting on OP to respond with his traceroute results.
    – Davan
    Mar 24, 2015 at 20:43

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