Local ATM Address

The local ATM address is the 20-byte ATM address associated with a specific Classical IP instance. You must assign an ATM address to each Classical IP client and server, but you do not need to assign an ATM address on standalone (back-to-back) configurations. The following section describes ATM address formats and some of the SunATM software defined address variables.

ATM Address Formats and Variables

ATM addresses, like Network Service Access Point (NSAP) addresses, are 20 octets long, with each octet made up of 1 or 2 hexadecimal digits. The ATM address is divided into three fields: the End System Identifier field, the Selector field, and the Network Prefix field. The End System Identifier (ESI) field is a unique 6 octet value, which can be the IEEE hardware MAC address conventionally associated with every network interface. The Selector field is one octet long. The 13 octets that make up the rest of the ATM address are called the Network Prefix. This field should be derived from the ATM switch fabric to which the interface is connected. Every ATM switch fabric is configured with a 13 octet prefix.

To simplify references to ATM addresses in the SunATM software, several system-defined variables are built into the software. Variables are referenced with the $ operator, as in UNIX shell scripts. Table 2-3 summarizes the system-defined SunATM address variables.

Table 2-3 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	Concatenation of $prefix:$mac:$sel, resulting in the default address for the local interface.
sunmacselN	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	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.

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Note -

The $prefix variable, and any other variables that use it (including $myaddress and $localswitch_server), can not be used on interfaces that are not running ILMI.

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ATM addresses are represented by 20 colon-separated octets, with each octet made up of 1 or 2 hexadecimal digits. You can combine variables representing portions of an ATM address with other variables and/or octets to make up a complete address. For example, $prefix:aa:bb:cc:dd:ee:ff:$sel represents a valid ATM address.