Using Variables in the /etc/opt/SUNWconn/atm/aarconfig File (Platform Notes: The SunATM Driver Software)

Platform Notes: The SunATM Driver Software

Using Variables in the `/etc/opt/SUNWconn/atm/aarconfig` File

Because the prefix portion of an ATM address specifies the ATM switch, a number of hosts specified in an aarconfig file can have ATM addresses that share the same prefix. To simplify setting up the aarconfig file, you can define variables that contain part of an ATM address.

A variable's name is an identifier consisting of a collection of no more than 32 letters, digits, and underscores. The value associated with the variable is denoted by a dollar sign followed immediately by the variable name.

Note -

Use variables in the ATM address field only. They are not valid in any of the other fields in an entry.

You can use a colon to concatenate multiple variables to represent a single ATM address expression. Thus, if one variable, v1, is set to 11:22 and another variable, v2, is set to 33:44, the sequence $v1:$v2 represents 11:22:33:44. You can include hexadecimal numbers with variables in the expression. The expression 45:$v1:$v2 would have the value 45:11:22:33:44.

Use the following format to define variables in the aarconfig file:

set VARIABLE = EXPRESSION

where VARIABLE is the name of a variable and EXPRESSION is an expression concatenating one or two-digit hexadecimal numbers or the values of variables that have been previously defined. The equal sign is optional, but separate the variable and expression either by white space (spaces or tabs), an equal sign, or both.

Several predefined variables are built into the SunATM software. These variables are summarized in Table 3-2.

Note -

You can not use the $prefix variable or any other variables that use it (including $myaddress and $localswitch_server) on interfaces that are not running ILMI.

Table 3-2 Predefined SunATM Variables


Variable	Description
`prefix`	The 13-byte prefix associated with the local switch.
`mac`	The 6-byte medium access control (MAC) address associated with the local host or interface.
`sel`	The default 1-byte selector for the local interface.
`macsel`	The concatenation of `$mac:$sel`.
`myaddress`	The concatenation of `$prefix:$mac:$sel`, resulting in the default address for the local interface.
`anymac`	A wild card representing any 6-byte ESI. Should only be used in a entries.
`anymacsel`	A wild card representing any 7-byte ESI and Selector combination. Should only be used in a entries.
`?`	A wild card matching one or two hexadecimal digits within any colon-separated field. For example, `$prefix:$anymac:?` is equivalent to both `$prefix:$anymac:??` and `$prefix:$anymacsel`. However, it is not the same as `$prefix:$anymacsel:0?`, which requires that the first digit of the selector byte is a `0`. This wild card should only be used in a entries.
`sunmacsel`N	The concatenation of one of a series of reserved MAC addresses and `$sel` to create a block of reserved ATM ARP server addresses. N should be a decimal number in the range 0-199.
`localswitch_server`	The concatenation of `$prefix`, a unique reserved MAC address, and `$sel`. When used as a server address, restricts server access to clients connected to the local switch only.

In most network configurations, the ATM address assigned to the local interface is $myaddress; using this variable in the l entry makes it possible to use identical aarconfig files on all Classical IP clients using a given server.

The sunmacselN variables can be used in conjunction with a prefix, as well as with known server addresses that are not bound to a particular system. As an example, consider the case where a server that supports 50 clients fails. If the ATM address of the server is specific to that particular server, you must change the s entry on all 50 clients to switch to a backup server. However, if the ATM address used for that server is $prefix:$sunmacsel3, this address is not only guaranteed to be unique, since it uses reserved medium access control (MAC) addresses, you can also simply assign that address to the backup server on the same switch by changing the l entry to an s entry on one system and bringing up a new server with no changes to the clients.

Note -

The sunmacselN variables do not include a prefix since a client and server may be on different switches and thus have different local prefix values.

In the case of a single-switch network, you can use localswitch_server as a well-known server address that includes the prefix associated with the local switch and a MAC address. It will restrict server access to clients on the local switch and provide a unique ATM address among all ATM clients connected to that switch. Thus, any host with a network prefix other than that of the local switch will be refused a connection to the ARP server if the ARP server's address is $localswitch_server.

Several rules apply to the use of variables in the aarconfig file:

Two variables cannot follow each other in an expression without an intervening colon. Thus $v1:$v2 is legal while $v1$v2 is not.
Fields in each line in the aarconfig file are separated by white space. Therefore, variables should not be separated from the rest of an ATM address with white space. For example, $v1: $v2 is illegal.
Once a variable is defined by a set command, it may not be redefined later in the same configuration file.
The reserved variable names cannot be set. These names include prefix, mac, sel, macsel, myaddress, anymac, anymacsel, sunmacselN (where N is a number between 0 and 199), and localswitch_server.

Note -
The ESI portion of localswitch_server and the sunmacselN variables is a reserved MAC address. The hexadecimal values of the reserved addresses are: localswitch_server 08:00:20:75:48:08 sunmacselNbase 08:00:20:75:48:10 To calculate the ESI portion for a sunmacselN address, simply add the value of N (converted to a hexadecimal number) to the sunmacselN base address. For example, the ESI portion of sunmacsel20 would be 08:00:20:75:48:10 + 0x14 = 08:00:20:75:48:24.