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You can limit the number of LU sessions that can be established from a client IP address.
This feature can control how many LU sessions a client IP address uses. For example, if a service bureau has 8000 clients and each client IP address is limited to four LU sessions, you will never need more than 32,000 concurrent LU definitions even when the service is running at 100 percent capacity.
This feature is supported on the following platforms:
This section describes the configuration tasks that are associated with the following LU limit feature:
This task is required. To establish a TN3270 server on the internal LAN interface on the CIP, perform the following tasks beginning in global configuration mode:
| Task | Command |
|---|---|
| Select the channel attach internal LAN interface and enter interface configuration mode. | interface channel slot/2 |
| Specify a TN3270 server on the internal LAN interface and enter TN3270 configuration mode. | tn3270-server |
| (Optional) Configure maximum number of LUs allowed. | maximum-lus max-number-of-lu-allocated |
| (Optional) Configure LU session limits for each client IP address or IP subnetwork address. | client [ip [ip-mask]] lu maximum number |
| (Optional) Configure transmission of a WILL TIMING-MARK. | timing-mark |
| (Optional) Assign a TCP port other than the default of 23. This command is also available in PU configuration mode. | tcp-port port-nbr |
| (Optional) Specify the idle time for server disconnect. This command is also available in PU configuration mode. | idle-time num-of-seconds |
| (Optional) Specify the maximum time allowed between keepalive marks before the server disconnects. This command is also available in PU configuration mode. | keepalive num-of-seconds |
| (Optional) Specify whether the TN3270 session will disconnect when an UNBIND command is received. This command is also available in PU configuration mode. | unbind-action {keep | disconnect} |
| (Optional) Select whether "left-over" LUs can be used from a generic LU pool. This command is also available in PU configuration mode. | generic-pool {permit | deny} |
When you use the tn3270-server command, you enter TN3270 configuration mode and can use all other commands in the task list. You can later override many configuration values you enter in TN3270 configuration mode from PU configuration mode. On IBM host systems, these types of commands are often referred to as "sift down" commands because their values can sift down through several levels of configuration and can be optionally altered at each configuration level.
This section documents new commands. All other commands used with this feature are documented in the Cisco IOS Release 11.2 command references. The following command has been added as a result of feature enhancements:
Use the client TN3270 configuration command to limit the number of LU sessions that can be established from a client IP address. Use the no form of this command to remove a single LU limit associated with a particular IP address.
client [ip [ip-mask]] lu maximum number| ip | (Optional) IP address of the client. The ip value is optional when setting the maximum number of LU sessions. If no IP address is specified then the limit is applied to all clients. |
| ip-mask | (Optional) IP network mask for the client. The default is 255.255.255.255 |
| number | (Optional and ignored in no form of the command) Maximum number of LU sessions. The allowed value is from 0 to 65535. |
The default is that there is no limit on the number of concurrent sessions to one client IP address.
In the no form of this command, the default number is 65535.
TN3270 configuration
This command first appeared in Cisco IOS Release 11.2 F.
An instance of the client (lu limit) command on a given tn3270-server is uniquely identified by the ip-mask and the logical AND of the ip address with that mask. For example, if the command is entered as
client 10.1.1.62 255.255.255.192 lu maximum 2
then it will be stored (and subsequently displayed by write term) as:
client 10.1.1.0 255.255.255.192 lu maximum 2
The maximum specified on the command can be changed simply by reissuing the command with the new value. It is not necessary to remove the command first.
When you use the no client command, only the corresponding client lu maximum statement is removed, as identified by the IP address and IP address mask combination. You cannot use no client to specify an unlimited number of LU sessions.
For example, if a service bureau has 8,000 clients and each client IP address is limited to four LU sessions, you will never need more than 32,000 concurrent LU definitions even when the service is running at 100 percent capacity.
The following example limits all clients to a maximum of two LU sessions:
client lu maximum 2
The following example limits a client at IP address 10.1.1.28 to a maximum of three LU sessions:
client 10.1.1.28 lu maximum 3
The LU limit can be applied to different subnets as shown in the following example. The most exact match to the client IP address is chosen. Clients with IP addresses that reside in the subnet 10.1.1.64 (those with IP addresses in the range of 10.1.1.64 through 10.1.1.127) are limited to a maximum of 5 LU sessions while other clients with IP addresses in the subnet 10.1.1.0 are limited to a maximum of 4 LU sessions.
client 10.1.1.0 255.255.255.0 lu maximum 4 client 10.1.1.64 255.255.255.192 lu maximum 5
The following example prevents an LU session for the client at IP address 10.1.1.28:
client 10.1.1.28 lu maximum 0
You can use the index or search online to find documentation of related commands.
maximum-lus
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