For the 2nd ethernet connection, the doco here (http://www.cisco.com/univercd/cc/td/doc/product/access/acs_soft/csacsapp/csapp33/install/ovrvuap.htm#wp1040777) gives the answer:
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Ethernet Connectors
Your system has two integrated 10/100/1000-megabit-per-second (Mbps) Ethernet connectors. Cisco Secure ACS Solution Engine supports the operation of either Ethernet connector, but not both connectors. Each Ethernet connector provides all the functions of a network expansion card and supports the 10BASE-T, 100BASE-TX, and 1000BASE-TX Ethernet standards.
Each NIC is configured to automatically detect the speed and duplex mode of the network.
Note The Cisco Secure ACS Solution Engine supports the operation of only one Ethernet connector at a time. Concurrent operation of both Ethernet connectors is not supported.
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For the shutdown issue, not sure, haven't seen that before.