Cisco Cisco 1800 2800 3800 Series 4-Port EtherSwitch High-Speed WIC
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The debug chat command can be used to enable debugs that will show if the cellular interface is able to set up a
connection. This log shows a successful connection:
ROUTER#debug chat
ROUTER#ping cisco.com
Translating "cisco.com"...domain server (72.163.4.161)
*Jan 31 00:03:41.514: CHAT0/0/0: Attempting async line dialer script
<snip>
*Jan 31 00:03:41.514: CHAT0/0/0: Chat script lte started
*Jan 31 00:03:41.514: CHAT0/0/0: Sending string: AT!CALL1
<snip>
*Jan 31 00:03:42.378: CHAT0/0/0: Chat script lte finished, status = Success
!Expected string, and received string has a match based on chat script parameters
<snip>
*Jan 31 00:03:45.378: %LINEPROTO-5-UPDOWN: Line protocol on Interface
Cellular0/0/0, changed state to up (198.224.174.135) [OK]
Cellular0/0/0, changed state to up (198.224.174.135) [OK]
<snip>
Other debugs that can be enabled are debug dialer and debug cellular x/x/x messages callcontrol.
For detailed troubleshooting and debug outputs, refer to the “Troubleshooting” section in the Cisco 4G LTE
Software installation guide:
5.6 4G as a Backup to Wired Primary WAN Connection
The most popular deployment in the enterprise world for a cellular WAN interface is backup. Enterprises have
adopted the 3G/4G cellular WAN connections as a backup to their primary connection such as Multiprotocol Label
resilient network in disastrous conditions, is an excellent backup WAN connectivity solution. Unlike wired WAN, it
has its own transport infrastructure from the router to the Internet, which provides excellent path diversity. When all
access is down because of natural disasters, cellular is often the only mode of communication for emergency
response and early disaster recovery. Cellular WWAN connection is integrated in the ISR, so it automatically takes
over when the primary WAN connection failure is detected. The most recommended method is based on Cisco IOS
Software object tracking. In this method, the primary WAN connection is tracked by sending end-to-end pings to
the far-end server/host. When the pings to the far end fail, the system concludes that the primary connection is not
working and the backup starts routing the packets appropriately.