ITEM: BO1291L

How to add multiple TCP/IP interfaces for AIX system running ATM.


Question:

I have heard that ATM allows me to configure multiple TCP/IP 
interfaces per adapter.  How can this be?

Response:

You heard correctly!  The ability to configure multiple IP addresses
of a single interface type and on a single adapter is unique to the
ATM driver.  Each TCP/IP interface on a RS/6000, regardless of the
network type, must be defined for a unique IP subnet.  We support up
to two ATM adapters per RS/6000 system unit and users can define
multiple TCP/IP interfaces which can be assigned independently to
either adapter.

With the ATM device driver for AIX V3.2.5, users can create up to 64
TCP/IP interfaces to ATM (at0 through at63) -- each with a unique IP
network address.  With AIX V4.1.4, users could, potentially, create up
to 256 ATM interfaces, numbered at0 through at255.

We find today's ATM users configure just a few interfaces and AIX
V4 users can create up to eight interfaces without taking any special
steps.  However, users needing more than eight ATM interfaces on AIX
V4 will need to increase the "ifsize" option to the network options
("no") command prior to adding the ninth interface.  The default
ifsize value is 8, but it can be set to any number up to 256.  This
option is NOT set dynamically.  Therefore, users should type this
command in the /etc/rc.net file, PRIOR to the interface bringup
routines.

CAUTION:  the ifsize option (just like all the "no" options) affects
all TCP/IP interfaces on the system.  Setting an artificially high
value for ATM means additional system resources will also be reserved
for other TCP/IP interface types (such as Token-Ring or Ethernet).
An excessively high value will waste ATM and other LAN resources.


Support Line: How to add multiple TCP/IP interfaces for AIX system running ATM. ITEM: BO1291L
Dated: September 1996 Category: N/A
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