Cisco Gigabit Switch Router 12008 Installation And Configuration Manual page 156

Connecting Route Processor Cables
Note
maximum usable bandwidth that is less than 100 Mbps; a maximum usable bandwidth of
approximately 20 Mbps should be expected from either the RJ-45 or MII connections.
Transmission speed is determined by the network to which the Ethernet interface is
connected and is not user-configurable.
Figure 3-8
To repeater
or DTE
To transceiver,
repeater, or DTE
Both the MII and RJ-45 receptacles support IEEE 802.3u Ethernet interfaces compliant
with the 100Base-TX and 10Base-T standards. The MII receptacle requires an external
transceiver that permits connection to multimode fiber for 100Base-FX or 100Base-T4
physical media. Only one Ethernet receptacle, either RJ-45 or MII, can be used at a time.
Two LEDs on the GRP faceplate show which Ethernet receptacle is active.
Note
cables. In sites where extremely high immunity to noise is required, screened twisted-pair
cable is recommended.
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Cisco 12008 Gigabit Switch Router Installation and Configuration Guide
At the auto-sensed data transmission rate of 100 Mbps, the Ethernet port provides
RJ-45 and MII Ethernet Connections
RJ-45 cable
MII cable
The Ethernet port can use either unshielded twisted-pair or screened twisted-pair