CICS Transaction Gateway V5 The WebSphere ... - IBM Redbooks

The IP address mask should be set to the hexadecimal version of your IP subnet
mask. This will ensure that the LU name generated is unique within your local IP
subnet. We used FFFFFE00, the hexadecimal value of our TCP/IP subnet mask
255.255.254.0. To determine your IP address and TCP/IP subnet mask, you can
use the Windows ipconfig /all command as shown in Example 3-2.
Example 3-2 ipconfig utility
C:> ipconfig /all
Windows 2000 IP Configuration
Host Name . . . . . . . . . . . . : volga
Primary DNS Suffix . . . . . . . : almaden.ibm.com
Node Type . . . . . . . . . . . . : Hybrid
IP Routing Enabled. . . . . . . . : No
WINS Proxy Enabled. . . . . . . . : No
DNS Suffix Search List. . . . . . : itso.ibm.com
almaden.ibm.com
Ethernet adapter Local Area Connection 3:
Connection-specific DNS Suffix . :
Description . . . . . . . . . . . : Intel(R) PRO/100 VE Desktop Connection
Physical Address. . . . . . . . . : 00-02-55-4A-7A-67
DHCP Enabled. . . . . . . . . . . : No
IP Address. . . . . . . . . . . . : 9.1.38.39
Subnet Mask . . . . . . . . . . . : 255.255.254.0
Default Gateway . . . . . . . . . : 9.1.38.1
DNS Servers . . . . . . . . . . . : 9.1.8.254
9.14.1.30
IP subnets: The subnet is the mask that is applied to an IP address to
determine which bits in an IP address are to be used for local addresses (that
is, addresses on the local subnet) and which bits are to be used for the
network address (that is, on the Internet). Thus, with our subnet mask of
255.255.254.0 (or in binary 11111111.11111111.11111110.00000000) we
have 8 bits free in the fourth byte (0) and 1 bit free in the third byte (254),
giving a total of 9 free bits. This means that we have 2 9 or 512 unique network
addresses available in the subnet.
For each substitution character the TCP62 hashing algorithm uses 5 bits from
the IP address. The CICS connection autoinstall program (DFHZATDY) uses the
last four characters of the LU name to generate the connection name, which has
to be unique within the CICS region. Therefore, if you wish to ensure that the
Chapter 3. TCP62 connections to CICS 49