[SOLVED] Unable to access network, i.e. Internet, beyond router

Issues related to configuring your network
levron
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Joined: 2011/11/04 14:38:37
Location: Texas

Re: Unable to access network, i.e. Internet, beyond router

Post by levron » 2011/11/11 23:08:46

(under scores added for clarity)

== BEGIN route -n ==
Kernel IP routing table
Destination_______Gateway_______Genmask_______Flags_______Metric_______Ref_______Use_______Iface
192.168.0.0_______0.0.0.0________255.255.255.0___U__________0____________0________0_________eth0
192.168.122.0_____0.0.0.0________255.255.255.0___U__________0____________0________0_________virbr0
169.254.0.0_______0.0.0.0________255.255.0.0_____U__________1002_________0________0_________eth0
0.0.0.0___________192.168.0.250__0.0.0.0_________UG_________0____________0________0_________eth0
== END route -n ==



[root@***** ~]# cat /etc/resolv.conf
# Generated by NetworkManager
nameserver 192.168.1.254
[root@***** ~]#

mmoryto
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Location: Cracow, Poland

Re: Unable to access network, i.e. Internet, beyond router

Post by mmoryto » 2011/11/11 23:51:57

What is 192.168.1.254 ?
Did you try to use tcpdump/wireshark to sniff if you get DNS replies from this IP ?

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jlehtone
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Re: Unable to access network, i.e. Internet, beyond router

Post by jlehtone » 2011/11/12 00:06:03

[quote]levron wrote:
My CentOS 6 server is wired to a remote switch located 1 hop down from the router and shared by 2 Windows PCs. I can ssh and remote desktop via tightvnc from my Windows box to my new install but cannot get out of my local network to the Internet. If I connect the CentOS directly into the router ...[/quote]
First, a side question: what is in /etc/sysctl.conf and are there anything connected to the virbr1?

Then, I'm trying to draw your network. Correct if wrong:

Can ssh, but no inet:
[code]INET--router--switch--Windows
|
CentOS[/code]
No ssh:
[code]INET--router--switch--Windows
|
CentOS[/code]
What is that "remote switch"? Does it have the default gateway address? Is "router" then the DNS?

levron
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Joined: 2011/11/04 14:38:37
Location: Texas

Re: Unable to access network, i.e. Internet, beyond router

Post by levron » 2011/11/12 00:06:36

192.168.1.254 is my AT&T/Motorola DSL modem. I will investigate the tcpdump/wireshark and report back

levron
Posts: 12
Joined: 2011/11/04 14:38:37
Location: Texas

Re: Unable to access network, i.e. Internet, beyond router

Post by levron » 2011/11/12 15:34:42

network configuration

Inet------ATT/Motorola modem(192.168.1.254)-----Linksys Cisco Router(192.168.0.250)------D-Link 5 port Switch------ 2 Windows boxes


CentOS was connected to the D-Link in first configuration and directly to the Linksys in the second.

Tracert from the Windows box doesn't show the D-Link switch so it's acting more like a hub in that respect.

Should I add the DNS from my DSL provider?

mmoryto
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Location: Cracow, Poland

Re: Unable to access network, i.e. Internet, beyond router

Post by mmoryto » 2011/11/13 09:54:17

Try to use static parameters:
IP: 192.168.0.106
Subnet mask: 255.255.255.0
Gateway: 192.168.0.250
DNS: 8.8.8.8 and 8.8.4.4

You should have NetworkManager stopped, otherwise you won't be able to set DNS.

pschaff
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Re: Unable to access network, i.e. Internet, beyond router

Post by pschaff » 2011/11/13 10:39:42

[quote]
mmoryto wrote:
Try to use static parameters:
...
You should have NetworkManager stopped, otherwise you won't be able to set DNS.[/quote]
I would not do that just yet. There are three different non-routing subnets shown:
192.168.0.0/24
192.168.1.0/24
192.168.122.0/24

As the ATT/Motorola modem is providing 192.168.1.0/24 subnet, and you are trying to use it as a router, I suspect it has router/DHCP/DNS servers built in. Remove the Linksys Cisco Router and try the switch connected directly to the ATT modem, and try configuring everything with DHCP. You have [url=http://www.google.com/search?q=double+NAT&ie=utf-8&oe=utf-8&aq=t&rls=org.mozilla:en-US:official&client=firefox-a]double/triple NAT[/url] in the current setup.

levron
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Location: Texas

Re: Unable to access network, i.e. Internet, beyond router

Post by levron » 2011/11/13 22:32:53

I am updating this from my CentOS Linux server which means that pschaff is nothing short of a genius!! Setting the DSL modem as a bridge resolved the double NAT condition and it will be interesting to see if some of my other anomalous Internet issues get resolved because of this. Many thanks to all who gave my issue consideration and submitted ideas.

pschaff
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[SOLVED] Unable to access network, i.e. Internet, beyond rou

Post by pschaff » 2011/11/14 16:32:33

Thanks for reporting back and for the effusive complement. Not exactly the solution I proposed, but changing the DSL router to bridge mode effectively removed one router from the picture. Glad we could help. Marking this thread [SOLVED] for posterity.

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