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--- networking:cisco-1921 [20/06/2025 17:04] – andrew
+++ networking:cisco-1921 [22/09/2025 15:55] (current) – [Optical Network Terminator] andrew
@@ Line 1: / Line 1: @@
 ====== Cisco 1921 Gigabit router ======
+{{:networking:cisco1921.png?400 |Cisco 1921}}
+Replaces [[cisco-1841|Cisco ADSL & 1841 router]] as this is a Fast Ethernet only router, the 1921 is a similar router but with Ge0/0 and Ge0/1 interfaces and two hwic slots. I have a EHWIC-1GE-SFP-CU card as well because in the foreseeable future I may need to bring the internet in from the ISP ONT some distance away, so a utp to fibre next to the ONT would link to the WIC SFP port.
+{{ :networking:cisco-ehwic-sfp.png?100|Without SFP module}}
+Note this is NOT a direct fibre from the ISP, it is  a single WDM fibre to the ONT, then a Ethernet to fibre converter and on to the 1941 SFP fibre in a different building.
-Replaces [[cisco-1841|Cisco ADSL & 1841 router]] as this is a Fast Ethernet only router, the 1921 is a similar router but with Ge0/0 and Ge0/1 interfaces and two hwic slots. I have a EHWIC-1GE-SFP-CU card as well because in the foreseeable future I will need to bring the internet in from the ISP ONT. Note this is NOT a direct fibre from the ISP, it is fibre to the ONT, then a Ethernet to fibre converter and on to the 1941 SFP fibre in a different building.
+{{:networking:ehwic-1ge-sfp.png?200|sfp fibre module fitted}}
+Also, there is a USB port in addition to the serial connector, this implements a usb to seial converter internally, it shows up as /dev/ttyACM0.
@@ Line 40: / Line 47: @@
 </code>
+Solution is to create the key. Many helpful posts on the various forums etc. BUT none seemed to specify the commands below needed to be run in the ''conf t'' session not just at the command line.
+<code>
+router01(config)#crypto key generate rsa modulus 2048
+The name for the keys will be: router01.rainsbrook.co.uk
+% The key modulus size is 2048 bits
+% Generating 2048 bit RSA keys, keys will be non-exportable...[OK]
+int-router01(config)#
+*Jun 20 15:24:41.599: %SSH-5-ENABLED: SSH 2.0 has been enabled
+router01(config)#
+</code>
+Banner text for a multiline statement is a bit unusual:-
+<code>
+router01(config)#banner login $
+Enter TEXT message.  End with the character '$'
++-------------------------------------------------------+
+|                                                       |
+|  Legal Warning - Access forbidden unless authorized   |
+|                                                       |
++-------------------------------------------------------+
+|             This is a private system and              |
+|      is only for the use of authorized personnel.     |
+|                                                       |
++-------------------------------------------------------+
+|                                                       |
+|  If you are allowed access, you will have been told.  |
+|    If you have to ask anyone if you are authorized,   |
+|                                                       |
+|                   -*YOU AREN'T*-                      |
+|                                                       |
++-------------------------------------------------------+
+$
+router01(config)#
+</code>
+====== Optical Network Terminator ======
+Just for completeness, this is the ONT. it has a single fibre input from OpenReach and a Gigabit ethernet port on an RJ45 for the Subs side interface.
+The technology used for this is GPON.
+[[https://www.draytek.co.uk/information/blog/gpon-fibre-fttp-what-is-it-and-how-does-it-work]]
+[[https://www.cisco.com/c/en/us/support/docs/switches/catalyst-pon-series/216230-understand-gpon-technology.html]]
+OpenReach ONT
+{{:networking:450px-fttp-ont-pon.jpg?100|}}
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