For 4500 E-series, the uplinks on the Supervisor Engine 6-E have three options in redundant mode operation.
1. The first option is referred to as 1 + 1 redundancy. In this configuration, only one 10 Gigabit Ethernet uplink port on each of the two supervisor engines carries traffic, and each port forwards traffic at line rate.
2. The second option is referred to as 2 + 2 redundancy; in this configuration, both 10 Gigabit Ethernet uplink ports on each of the two supervisor engines are forwarding traffic and the uplinks are 2:1 oversubscribed.
3. The third option is referred to as 4 + 4 redundancy. In this configuration, twin gigabit converter modules are used and all four Gigabit Ethernet uplink ports on each of the two supervisor engines carry traffic simultaneously at wire rate.
http://www.cisco.com/en/US/prod/collateral/switches/ps5718/ps4324/prod_white_paper0900aecd806ed38a.html
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Inayath
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