DHCP/Login Issue

Discussion in 'Cisco' started by joe.joesmith4j@gmail.com, May 17, 2006.

  1. Guest

    Hi,

    We are having an issue with DHCP and login to a Novell server whereby
    the clients can't find the tree. There seems to be some sort of timing
    issue when a computer boots, when the port on the switch becomes active
    and when the computer receives an IP address from the DHCP server.

    We thought that we had established a procedure whereby users could
    login 30 seconds after seeing Ctrl-Alt-Del. I'm told that some users
    have experienced problems even after 2 or 3 minutes.

    We have found out that if you try to login too soon it is possible for
    the computer not to have an IP address. If you then login to the local
    Windows machine (as opposed to Novell) and issue the appropriate dhcp
    release/renew commands, the IP is established. Then you can connect to
    Novell. However, this is too difficult for the average user as you
    might imagine.

    Does anyone have any suggestions on how we can eliminate this issue?
    Is there a way to guarantee that the IP address is established before
    Ctrl-Alt-Del is displayed? Do you think there is some other issue
    going on that we are not considering?



    Environment:

    - Core switches = Cisco 3750 (qty = two)
    - Access switches = Dell 5324 (qty = ten)
    - Client machines = Windows XP SP2

    All of the access switches are connected to both core switches. The
    DHCP servers are running on the core switches. The DHCP scope is split
    in half so that there is no conflict with IP addresses. There are 7
    VLANs of which 4 are setup for DHCP.

    The access ports (as opposed to trunk ports) on the Dell switches are
    configured with "spanning-tree portfast".

    All of the above is known internally as the new network as is running
    on 10.x networks.

    There is also an old (or current) network running on 192.168.x
    networks. The two networks are linked by a single cable running from
    one of the older switches (a Dell 5224) to one of the core switches.
    There is routing between the 10.x and 192.168.x networks, but I'm
    reasonably sure that no VLAN is passed back/forth. There is a DHCP
    server running on the old network on a Windows 2003 box, but the scope
    is only for the 192.168.x networks.

    Thanks,

    - Joe
     
    , May 17, 2006
    #1
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  2. thrill5 Guest

    Make sure all of your ports are configured with "spanning-tree portfast"
    What is happening is that your PC's are booting, the NIC is enabled and
    switch port comes up. Since portfast is NOT enabled, the port goes into
    blocking state for 30 seconds, so no traffic passes, and the PC won't get an
    IP address. "spanning-tree portfast" on the switch tells the port to start
    passing traffic immediately without waiting the normal 30 seconds to
    determine if a another spanning-tree device is on the other end. You should
    not enable this on ports that connect to other switches.

    On Windows98, NT and 2000, this problem was very rare because the boot up
    time of windows was much slower and the time elapsed between the NIC coming
    on and requesting a DHCP address was much longer.. XP boots pretty quick
    and this is a very common problem.

    Scott

    <> wrote in message
    news:...
    > Hi,
    >
    > We are having an issue with DHCP and login to a Novell server whereby
    > the clients can't find the tree. There seems to be some sort of timing
    > issue when a computer boots, when the port on the switch becomes active
    > and when the computer receives an IP address from the DHCP server.
    >
    > We thought that we had established a procedure whereby users could
    > login 30 seconds after seeing Ctrl-Alt-Del. I'm told that some users
    > have experienced problems even after 2 or 3 minutes.
    >
    > We have found out that if you try to login too soon it is possible for
    > the computer not to have an IP address. If you then login to the local
    > Windows machine (as opposed to Novell) and issue the appropriate dhcp
    > release/renew commands, the IP is established. Then you can connect to
    > Novell. However, this is too difficult for the average user as you
    > might imagine.
    >
    > Does anyone have any suggestions on how we can eliminate this issue?
    > Is there a way to guarantee that the IP address is established before
    > Ctrl-Alt-Del is displayed? Do you think there is some other issue
    > going on that we are not considering?
    >
    >
    >
    > Environment:
    >
    > - Core switches = Cisco 3750 (qty = two)
    > - Access switches = Dell 5324 (qty = ten)
    > - Client machines = Windows XP SP2
    >
    > All of the access switches are connected to both core switches. The
    > DHCP servers are running on the core switches. The DHCP scope is split
    > in half so that there is no conflict with IP addresses. There are 7
    > VLANs of which 4 are setup for DHCP.
    >
    > The access ports (as opposed to trunk ports) on the Dell switches are
    > configured with "spanning-tree portfast".
    >
    > All of the above is known internally as the new network as is running
    > on 10.x networks.
    >
    > There is also an old (or current) network running on 192.168.x
    > networks. The two networks are linked by a single cable running from
    > one of the older switches (a Dell 5224) to one of the core switches.
    > There is routing between the 10.x and 192.168.x networks, but I'm
    > reasonably sure that no VLAN is passed back/forth. There is a DHCP
    > server running on the old network on a Windows 2003 box, but the scope
    > is only for the 192.168.x networks.
    >
    > Thanks,
    >
    > - Joe
    >
     
    thrill5, May 18, 2006
    #2
    1. Advertising

  3. thrill5 Guest

    Make sure all of your ports are configured with "spanning-tree portfast"
    What is happening is that your PC's are booting, the NIC is enabled and
    switch port comes up. Since portfast is NOT enabled, the port goes into
    blocking state for 30 seconds, so no traffic passes, and the PC won't get an
    IP address. "spanning-tree portfast" on the switch tells the port to start
    passing traffic immediately without waiting the normal 30 seconds to
    determine if a another spanning-tree device is on the other end. You should
    not enable this on ports that connect to other switches.

    On Windows98, NT and 2000, this problem was very rare because the boot up
    time of windows was much slower and the time elapsed between the NIC coming
    on and requesting a DHCP address was much longer.. XP boots pretty quick
    and this is a very common problem.

    Scott

    <> wrote in message
    news:...
    > Hi,
    >
    > We are having an issue with DHCP and login to a Novell server whereby
    > the clients can't find the tree. There seems to be some sort of timing
    > issue when a computer boots, when the port on the switch becomes active
    > and when the computer receives an IP address from the DHCP server.
    >
    > We thought that we had established a procedure whereby users could
    > login 30 seconds after seeing Ctrl-Alt-Del. I'm told that some users
    > have experienced problems even after 2 or 3 minutes.
    >
    > We have found out that if you try to login too soon it is possible for
    > the computer not to have an IP address. If you then login to the local
    > Windows machine (as opposed to Novell) and issue the appropriate dhcp
    > release/renew commands, the IP is established. Then you can connect to
    > Novell. However, this is too difficult for the average user as you
    > might imagine.
    >
    > Does anyone have any suggestions on how we can eliminate this issue?
    > Is there a way to guarantee that the IP address is established before
    > Ctrl-Alt-Del is displayed? Do you think there is some other issue
    > going on that we are not considering?
    >
    >
    >
    > Environment:
    >
    > - Core switches = Cisco 3750 (qty = two)
    > - Access switches = Dell 5324 (qty = ten)
    > - Client machines = Windows XP SP2
    >
    > All of the access switches are connected to both core switches. The
    > DHCP servers are running on the core switches. The DHCP scope is split
    > in half so that there is no conflict with IP addresses. There are 7
    > VLANs of which 4 are setup for DHCP.
    >
    > The access ports (as opposed to trunk ports) on the Dell switches are
    > configured with "spanning-tree portfast".
    >
    > All of the above is known internally as the new network as is running
    > on 10.x networks.
    >
    > There is also an old (or current) network running on 192.168.x
    > networks. The two networks are linked by a single cable running from
    > one of the older switches (a Dell 5224) to one of the core switches.
    > There is routing between the 10.x and 192.168.x networks, but I'm
    > reasonably sure that no VLAN is passed back/forth. There is a DHCP
    > server running on the old network on a Windows 2003 box, but the scope
    > is only for the 192.168.x networks.
    >
    > Thanks,
    >
    > - Joe
    >
     
    thrill5, May 18, 2006
    #3
  4. Guest

    Thanks for the reply. I believe I did mention that we are using
    "spanning-tree portfast" on the ports for the clients (PC) computers.
    Or did you mean something else?

    Meanwhile, we may have solved the problem by upgrading our Novell
    client to the latest version.

    Novell Client for Windows NT/2000/XP v4.91 (Recommended)
    File Name Document Title Creation Date
    nc491sp2.exe Novell Client 4.91SP2 for Windows2000/XP/2003 10JAN2006

    - Joe
     
    , May 20, 2006
    #4
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