NLB Host addres problem
I have configured NLB on windows 2008 Server (x86) 32 bit OS. Everything was working fine till now. Since 2 days The NLB manager is showing a error on one of the host as unreachable and log error as "Error code 0x80041001. Error connection to "localhost"". What could be the problem.mmyaseen
July 19th, 2011 8:17am

The NLB does exist and it is checked. I closed and opened the NLB Manager and tried to connect to the cluster, it is giving error "Error code 0x80041001". Also if I browse the application hosted in IIS through Cluster IP i can see the application going to the host address which is giving error.mmyaseen
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July 21st, 2011 6:16am

Hi mmyaseen, Thank you for your update. I remember the 0x80041001 error is caused by NLB node1 cannot communicate with NLB node2. Please try following suggestions: 1. Check node2 firewall setting, if necessary disable firewall to test 2. Reboot node2 server to test 3. On node1, visit UNC \\node2, ping node2, telnet node2. If failed, use Netmon to monitor TCP packet, find the reason TCP connection not establish (like suspicious mac address) If there are more inquiries on this issue, please feel free to let us know.Regards, Rick Tan
July 21st, 2011 11:04pm

Hi Rick, Thank your for your reply. I did a ping to the host which is showing unreachable from the second host. The reply was from IPV6 not IPV4. I disabled the IPV6 on the first host, now I am getting reply in IPV4. Still I am getting the same error. Is is something to do with the DNS? DNS on both the Hosts are different. Regards Yaseen D M mmyaseen
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July 22nd, 2011 12:51am

Hi mmyaseen, Suggest to set up host ip address in the NLB Manager, so just ping host ip address to test the network connectivity. If it failed, run "tracert ip address" to check icmp stop on which hops or use netmon to monitor the tcp packet. Regards, Rick Tan
July 22nd, 2011 1:15am

The ping is working and network connectivity is ok.mmyaseen
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July 22nd, 2011 2:47am

Hi mmyaseen, It's also point to icmp issue from NLB troubleshooting guide, please double test or you need to remove & add the error host into NLB cluster. When attempting to use Network Load Balancing Manager to connect to a host in your cluster, you receive the error "Host unreachable." Cause: Internet control message protocol (ICMP) to the host is either blocked by a router or firewall or disabled on the host's network adapter. Solution: Enable ICMP on the host's network adapter or allow ICMP traffic through the firewall or router. Be aware that this may expose your system to additional security risk. You can also use NLB Manager's /noping option. Regards, Rick Tan
July 22nd, 2011 5:08am

Hi Rick, I tried all this, but no success. In NLB the unreachable host was getting listed with error but now it is even not getting listed. Is it something to do with the DNS. Because there two hosts under on Cluster. Both the hosts have different DNS. mmyaseen
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July 25th, 2011 12:11pm

Hi mmyaseen, Is it something to do with the DNS. Because there two hosts under on Cluster. Both the hosts have different DNS. You mean hosts DNS name in Cluster are not the server hostname? Run command "ipconfig /flushdns" to purge DNS cache on both servers, then test ping hosts DNS name on each server.Regards, Rick Tan
July 26th, 2011 1:53am

Hi Rick I tried ipconfig /flushdns, still i get host unreachable error. Even i tried running NLB manager with /noping option still the host is not getting listed in NLB manager. This is getting more and more critical. I am not understanding what could be the issue? mmyaseen
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July 26th, 2011 3:28am

Hi, Check for disabled services. I had same problem, and my problem was in disabled "Windows module installer" service. After enabling - it comes ok.
July 23rd, 2012 10:45am

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