You might look at using a BVI, bridged virtual interface if you are trying to "connect" routed ports. With a BVI you are adding the routed interfaces to a bridge group as in a Layer 2 bridge back in the old days of the Ethernet.
Check out this link for more help:
http://www.cisco.com/univercd/cc/td/doc/product/l3sw/8540/rel_12_0/wx5_11a/config/7cfg8500.htm
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