Win 2003: Unable to connect to cluster via NLB manager

Discussion in 'Server Networking' started by Condor, Aug 22, 2007.

  1. Condor

    Condor Guest

    I've configured NLB on two Win 2k3 servers. These servers have two NIC's. NLB
    is configured on the front end lan (EFL) only. From a standalone server which
    has 'visibility' to this cluster - I'm able to ping both the individual
    hosts, ping the EFL Cluster IP (by cluster name and IP). I ran a netmon trace
    and it indicated that my packets are being answered to. However, when I try
    to connect to this cluster (by name or IP) from the NLB manager of the
    standalone server (I mentioned above) I get the message that "NLB is not
    loacted on the specified computer". I have an application that needs to
    connect via this "application NLB cluster" to login to the DB - which does
    not go through. I'm beginning to believe that this has something to do with
    the above issue.

    Any pointers on how to solve this would be greatly appreciated.

    Thank you.
    Condor, Aug 22, 2007
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  2. Hello,

    I think you have two issues
    -Access the NLB from the MMC
    -access to a specific port on the NLB IP.

    As the NLB IP is binded and reachable, i think you forgot to add the needed
    TCP port on the NLB, like the 1433 for SQL.

    On one node, click to add existing nlb. Type as server to join.
    Does it work ?

    Why are you speaking of two network card ?
    Does the DB bind on all interfaces (netstat -an will help) ?
    Mathieu CHATEAU, Aug 23, 2007
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  3. Condor

    Condor Guest

    Thanks Mat. I checked and the ports which my app needs are 80, 443 and 135 -
    these are already added to NLB config. NLB with works good...

    I have an entry in the hosts file as well. 'UATRTCAPP' is the name of the
    cluster. uatrtcapp

    I'm not a pro at this stuff but when I meant two network cards - I meant
    each node is on 2 LANS - front end (EFL) and back end (EBL). Clustering is
    done only on the EFL. Not sure how relevant it is to the current issue,

    Another thing is I can ping each node (from 3rd server) in the cluster and
    'UATRTCAPP' from the third server which has visibility to the cluster. But
    when I try to connect to 'UATRTCAPP' from NLB manager I always get 'Could not
    locate NLB on specified computer'.

    One more interesting thing is when I reboot the third 'server' and
    immediately try to log into my app, it goes through. This is because NLB
    manager from the third server identifies 'UATRTCAPP' But after some time,
    login fails and NLB manager now gives 'Could not locate NLB.......' - same
    error as above. Looks like it is intermittent. I'm currently digging thru the
    Event viewer to see if I can find any errors.

    Hope my explanation is not confusing. Any pointers are greatly appreciated.
    Condor, Aug 28, 2007
  4. Condor

    Condor Guest

    I forgot to add, my app's logs show the below error. The app is on the 3rd
    server and it needs to connect to the below mentioned 'cluster' to access the
    DB. I figured out that the connection to DB is not even coming through, since
    it is not even making it to the cluster...

    -2147023174 - The RPC server is unavailable. Looks like a system error but a
    reboot did not help. I need to figure out what this means.

    Condor, Aug 28, 2007
  5. Are these 3 servers (2 NLB and the third) in a domain ?
    Services are working through the nlb, it's just the nlb manager that you
    want to get from remote ?
    Mathieu CHATEAU, Aug 28, 2007
  6. Condor

    Condor Guest

    Yes, they are all in one domain. I just need to connect to 'UATRTCAPP'
    cluster from the NLB of the third machine. If this goes through, the login
    for my app also goes through. I am able to ping UATRTCAPP and it resolved to
    the correct 10.253.x.y IP, though. I get the same 'Cannot locate NLB......'
    error when I try to 'Connect to existing' from NLB manager.

    Condor, Aug 29, 2007
  7. did you try to connect to the nlb by using the real ip of one of the two
    Mathieu CHATEAU, Aug 30, 2007
  8. Condor

    Condor Guest

    NLB with real IP of the first server in the cluster goes through fine. If I
    try to connect with the real IP of the second server, it throws "Could not
    locate NLB on the specified computer". NLB is installed and configured on the
    second server as well.
    Condor, Aug 30, 2007
  9. does this server has netbios removed or disabled ?
    Are you in unicast with one network card ?
    Mathieu CHATEAU, Aug 30, 2007
  10. Condor

    Condor Guest

    Yes, NETBIOS is disabled (per security policy on the EFL which is internet
    facing) but is enabled on the EBL - on both the servers. Each server has 2
    NIC's (one for EFL and one for EBL) and clustering is in unicast mode on both
    Condor, Aug 30, 2007
  11. and so you connect with nlbmgr through the EBL ?
    Mathieu CHATEAU, Aug 30, 2007
  12. Condor

    Condor Guest

    Yes, from the third server (which is an application client) I test/connect
    the 'UATRTCAPP' NLB cluster via the EBL.

    Condor, Aug 31, 2007
  13. So you have admin rights on the two through your AD Domain, but one is
    working and not the other?
    Can you check about differences between the two ?
    -network card orders
    -network card config
    -services on the network card
    -windows services started

    I just sniffed the network while trying to connect to nlb:
    -it send pings
    -it try NbtNS (netbios name service)
    -then through TCP port 135

    So netbios is the key to get the console manager working
    Mathieu CHATEAU, Aug 31, 2007
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