I know this is a little old but I will add what I know. I have been testing these 4G cards since September 2011 or so. Originally I could *only* get 4G to work because VZW did not have the ESN's in their system so I could simply swap out the SIM card. Sometime during spring '12 VZW finally approved the cards and the ESN's went active. Since 3G is CDMA based and 4G is GSM you must have the correct ESN provisioned with VZW for the 3G to work. So, if you simply took a active 4G SIM from a device and put it in the WIC card this could be why you see your 4G work fine and then when in a non-4G area you can't go backwards to 3G.
I know that may be very basic information to many and you may already know all this, but with so little user documentation out there on these cards I figured I would add that so maybe it will help you or maybe it will help future users.
On the subject of the cards not connecting and staying at -125db I too have this problem. Of my 7 or so cards in production I have seen this occur on every one of them, so when Cisco says "a small subset" I think may a bit optimistic on their part. My cards were purchased over a 4 month period so I don't think they all came from the same lot, etc. According to TAC, a similar problem existed originally with the 3G version of these cards and it took a while for our lovely FCC to approve some changes to fix it. Below is the SLA commands I use to keep mine up:
event manager applet cell_rset authorization bypass
event track 234 state down
action a syslog msg "EEM Cellular modem reset"
action b cli command "enable"
action c cli command "config terminal"
action d cli command "service internal"
action e cli command "end"
action f cli command "test cellular 0/0/0 modem-power-cycle"
action g cli command "wait 10"
action h cli command "end"
action i cli command "ping x.x.x.x"
action j cli command "clear crypto session"
!
track 234 ip sla 2 reachability
delay down 10
!
ip sla 2
icmp-echo x.x.x.x source-interface Cellular 0/0/0
frequency 5
ip sla schedule 2 life forever start-time now
Simply change x.x.x.x to an IP address that is accessible from your 4G card. Action J is for my system because I use the card to create IPSEC tunnel. If you are doing the same I suggest you keep this in there as I had numerous issues with the tunnel not coming back up after the recovery ran. Don't know why - maybe it is something I have wrong.
In my case my WIC is always live and has a few specific route statements in there that direct specific traffic over the 4G connection all the time, so if you are doing the same make sure your x.x.x.x address is *always* set to go across the 4G, otherwise you will be testing your primary WAN connection and not the 4G, so you will never know if the 4G is up or down.
Occasionally this script will not fix the problem - in my experience this is less than one time per month, per device. I do not take the script all the way to a reload because it isn't worth it to kick my users out to fix it. I do have Nagios running that monitors the status of the card and sends me a warning when it is reporting "Dormant" and then I can schedule a manual reload which in all cases has cleared the problem and returned the device to a working state.
Maybe this helps - maybe it doesn't.
John
