In order to have support for the Broadcom BCM5709S network card a driver must be added. This driver can be downloaded from the Broadcom web site.
Download the Solaris GLDv3 driver(version 4.4.3). In order to do a network install the mini-root must be patched to allow Solaris to install over the network using this network card and you must follow the post-install workaround to add the driver to the system after the initial install.
The post-install workaround is to download the driver, do a pkgrm BRCMbnx to remove the current bnx driver, and then do a pkgadd on the new version 4.4.3 BRCMbnx package.