Trouble with networking a Linux RedHat server

amaru96
amaru96 used Ask the Experts™
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Hi guys, I have almost zero experience with Linux so please bear with me.

I've been asked to deploy a server running RedHat Enterprise 5 within our VmWare environment. I have installed RedHat and everything seems fine, However, I am unable to get the networking side of things to work properly.

I've assigned it an IP address and from the Linux server itself I can open up a terminal and ping itself but that is all I can ping. I can't ping anything else on the network, including other servers on the same subnet or the gateway.

I also tried changing it from using a static IP to DHCP. It receives an IP address from the DHCP server but again the same result. The server can ping itself but nothing else.

When I do try to ping another address it says "From myipaddress icmp_seq=1 Destination Host Unreachable"

Any advice would be much appreciated.
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Luciano PatrãoICT Senior Infraestructure  Engineer  

Commented:
Hi

First what VMware are you using? ESX?? Workstation/Server?

Since your have no experience in Linux, check this articles to double check you Linux configuration

http://www.yolinux.com/TUTORIALS/LinuxTutorialNetworking.html

http://www.linuxhomenetworking.com/wiki/index.php/Quick_HOWTO_:_Ch03_:_Linux_Networking

Jail
Monis MontherSystem Architect

Commented:
Whats the output of the following command

ethtool eth0

Note: You should be root to run this command successfully
This sounds like it could possibly be connectivity related...

Check the VMWare network, make sure it's bridged with a physical adapter and that adapter is connected to the right switch/vlan.

If you've got a more complex VMWare network, with virtual switches and you're doing some tricky stuff there, that's something to check.

The linux installation sounds like its setup correctly from what you describe.  However, if you have multiple virtual adapters assigned to the VM, you could possibly have configured the wrong adapter.

Also, it is possible the device type for your adapter has an issue, not sure what edition/version of vmware you are using, but if you have choices for the network adapter type, you might switch that up... This will cause you to have to reconfigure the network.

Be sure to have installed VMWare tools as well.
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Commented:
I concur with the above, but would look first at the gateway.  Also, if I recall correctly, RedHat comes with a firewall configured.  turn that off for troubleshooting with this series of commands (as root):

# iptables -F
# iptables -X
# iptables -t nat -F
# iptables -t nat -X
# iptables -t mangle -F
# iptables -t mangle -X
# iptables -P INPUT ACCEPT
# iptables -P OUTPUT ACCEPT

Author

Commented:
It's running on vmware esx enviornment with multiple vlans. I have checked and it's on the right vlan.

I ran ethtool eth0, the result is:
Settings for eth0:
         Link detected: yes

Also ran the firewall commands from mccracky with no change.

I install vmware tools too

The strange thing is that from my computer if I run a constant ping to the linux server it responds a handful of times as it boots. Once the boot sequence ends and it prompts for a username the reply stops!

run

service iptables stop

Just for grins...   should do the same as iptables commands above... but...

Author

Commented:
ran service iptables stop, no change
Monis MontherSystem Architect

Commented:
also disable selinux

setenforce 0

Author

Commented:
Ran setenforce 0, no change. Does it need a reboot?
Luciano PatrãoICT Senior Infraestructure  Engineer  

Commented:
Hi

When installing the Linux you dont need to make any special changes on the Network. Just add the IP and is working. If you did not change anything, then this is working on the Linux side.

Lets focus on the VMware ESX.

You say that you have some VLANs. Is this VM using a standalone vSwitch? Or is using a vSwitch that has other VMs?

Can you please explain your VMware networking on the VM side?

Jail
Commented:
I stepped through the boot sequence and noticed that once the "xend" service was enabled the server stopped replying to my pings. I have disabled the xend service and all is fine now.

Not sure what that service does, but I can now communicate with the server!

Thanks for all your help guys.

Commented:
xend is the xen daemon for virtualization.  Were you trying to run nested virtual machines?  Virtual machines under linux with xen which itself runs in a virtual machine on vmware?

Author

Commented:
No, I wasn't running a nested VM. I deployed a new VM on an ESX server and installed RedHat directly on it.
Monis MontherSystem Architect

Commented:
mccracky: is correct, this is a nested virtual machine by mistake, you probably installed RHEL as default and you are booting with the kernel-xen.

Do you have 2 options to boot from , when the machine first comes up hit any key you should get the boot menu, you might find that there are 2 kernels , kernel-2.6.9 and kernel-xen-6.2.9. make sure you don't boot the kernel xen.

If this is the case let me know so I help you change the boot order from Grub

Author

Commented:
I don't actually get a boot option, I start the VM and it loads up, no menu appears with a choice.

Appreciate all the suggestions and help from everyone.
Luciano PatrãoICT Senior Infraestructure  Engineer  

Commented:
Hi

No warnings?? No errors??

Jail

Author

Commented:
Nope, boots up clean, no errors.
Luciano PatrãoICT Senior Infraestructure  Engineer  

Commented:
Hi

Are you sure? :)

Have you click on the screen console? Any movement?

Jail

Author

Commented:
Not sure what you mean?

The server boots up, RedHat loads and I can use it. I can also access it remotely.
Luciano PatrãoICT Senior Infraestructure  Engineer  

Commented:
Hi

Sorry I did not understand.

So what is the issue? The server work?

Jail

Commented:
Nothing we suggested even helped narrow down the issue?  Non of our troubleshooting actually helped?

Author

Commented:
Unfortunately not. I only discovered it by booting it in "interactive" mode and manually checking each service is it was brought online.

As I mentioned in one of my comments, I could ping the server while it boots but once it completed booting the replies stopped. So I knew something was changing or being executed during the boot up which prevented communications.

Only by chance did I see the message that said "Press I for interactive". I ran a continuous ping to the server as I slowly went through the services. It kept replying until I started the XEND service which then stopped. From that I figured the XEND service was in some way causing communication problems. I disabled the XEND service, rebooted and everything was fine, and still is.

Appreciate all the suggestions from everyone but they didn't really help solve my problem.

Commented:
Ok, fair enough.
Luciano PatrãoICT Senior Infraestructure  Engineer  

Commented:
Hi

Since points will not cost you nothing, sometimes I cannot understand some users.

But thats me.

Jail

Commented:
Restarting author's original action

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