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How to connect a Cisco Catalyst 6608 blade in Cisco CallManager even if the telephone company service provider refers to the T1/E1 interface as RJ48 or RJ45

Core Issue

Although the documentation of the Cisco Catalyst 6608 line card refers the to the T1/E1 port as an RJ48 interface, the service provider may sometimes refer to it as the T1/E1 line and a RJ45 interface since the connectors are almost the same.


As long as the telephone company service provider is referring this to the T1/E1 line (by either name), it is safe to connect the port to the provider's interface with a patch cord (even a RJ45 patch cord will do) as both these connectors have eight wires.

RJ48 is usually referred to the T1/E1 lines and RJ45 is commonly used in the LAN segments. The other main differences between the two are the following:

  • RJ48 has a keyed connector and a notched jack.
  • RJ45 does not have a key or a notch.
  • Both have eight pins.

Although an RJ45 connector fits in an RJ48 jack, the key on an RJ48 connector prevents it from plugging into an RJ45 jack.

How to Use Cisco CallManager to Configure a Catalyst WS-X6608-T1 Port as a T1 VoIP Gateway

TDM Signaling Type



Voice Gateway Hardware Components



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‎06-17-2009 10:13 PM
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