Cisco C819 4G LTE Connection Problems

[Njordic1429]

Hello everyone,

Our organization is running into a lot of issues in regards to this router.  We currently have five in production (will be 100) that are operational, but having constant connection problems with most of them. We've tried explaining to the organization that this is a signalling issue...and 4G rollouts will never be 100% up-time.

To give some details on the project, we're running two DMVPN tunnels (IKEv1) from the routers to two separate data-centers for redundancy.  We use Verizon 4G LTE SIM cards.  We're running CWS (Scansafe) on all routers, as well as a ZBF set up.  Here is the base configuration for the Cell interface and the dialer:

interface Cellular0

ip address negotiated

no ip redirects

no ip unreachables

no ip proxy-arp

ip verify unicast source reachable-via rx allow-default 100

ip nat outside

ip virtual-reassembly in

ip virtual-reassembly out

ip tcp adjust-mss 1400

zone-member security OUTSIDE

cws out

encapsulation slip

load-interval 30

dialer in-band

dialer idle-timeout 0

dialer string lte

dialer string LTE

dialer watch-group 1

async mode interactive

pulse-time 0

no shut

!

chat-script lte "" "AT!CALL" TIMEOUT 20 "OK"

chat-script LTE "" "AT!CALL1" TIMEOUT 20 "OK"

dialer watch-list 1 ip 5.6.7.8 0.0.0.0

dialer watch-list 1 delay route-check initial 30

dialer watch-list 1 delay connect 1

ip route 0.0.0.0 0.0.0.0 Cellular0

The set up other than the cell set up is the exact same to our brick and mortar setup. 

Is there anything I can adjust that will help with the constant cell signal bouncing or 30+ minute link up to the tower?

Any advice helps,

Thanks!

[Philip D'Ath]

I do a similar things with 897-4G's, and they are very reliable.

What are you using a dialer watch-list?

On my cellular interfaces I use "dialer idle-timeout 600 inbound". What this does is cause the cellular interface to self-reset after 10 minutes if no inbound traffic has been received.  Makes it mostly self healing.

I use EIGRP on all my routers (with dual DMVPN tunnels), and because of the EIGRP traffic there should never be a period of 10 minutes  no traffic is received for 10 minutes (due to EIGRP hello's).

I note you have two dialer strings defined.  You should only have one.

interface Cellular0
...
 dialer string lte
 dialer string LTE

I'm not familiar with your carrier, but I have found it is important to use an APN that provides direct internet access with a public IP address and no firewalling.  In my country each carrier offers a number of APNs you can use.  You may or may not that that option.

In case it helps, here is some exerts from my config:

chat-script spark "" "AT!SCACT=1,1" TIMEOUT 60 "OK"!

interface Cellular0
 ip address negotiated
 ip nat outside
 ip virtual-reassembly in
 zone-member security z-outside
 encapsulation slip
 dialer in-band
 dialer idle-timeout 600 inbound
 dialer string spark
 dialer-group 1

dialer-list 1 protocol ip permit

[Njordic1429]

Philip D'Ath,

Thanks for your insight.  I"ll be taking your advice into account and make some changes on our test environment.  I'll give an update once I've made some changes.

Thanks!

[Philip D'Ath]

How did you get on?

[Elliott Willink]

We had a few 819's with the Sierra Wireless 7710's in them (Check the sticker on the base of the unit).

I had to write an EEM script to remote-reboot them when the modem locked up. It is hands down the worst Cisco products we have ever purchased. At almost $2k a pop, it was a real shame to decommission the lot because of LTE modem lockups. The QMI firmware on the 7710 was an absolute bug-riddled joke.

This was about 18 months ago.. maybe the firmware is better now.. but we ended up selling them on eBay.

[johnlloyd_13]

hi,

what's the show cell 0 radio and show cell 0 network output on one of the router?

also include the dialer-group 1 under cell 0 interface and dialer-list 1 protocol ip permit in global config.

[Njordic1429]

johnlloyd_13,

Thanks for the response, currently all routers are off at the moment, I'll get that output when I'm able too.

I will also follow the advice by adding your two configuration changes.

Thanks!

[Njordic1429]

sh cell 0 radio
Radio power mode = ON
LTE Rx Channel Number =  5230
LTE Tx Channel Number =  23230
LTE Band =  13
LTE Bandwidth = 10 MHz
Current RSSI = -56 dBm
Current RSRP = -85 dBm
Current RSRQ = --7 dB
Current SNR = 14.0  dB
Radio Access Technology(RAT) Preference = AUTO
Radio Access Technology(RAT) Selected = LTE

Router#sh cell 0 network
Current System Time = Mon Apr 25 9:17:24 2016
Current Service Status = Normal
Current Service = Packet switched
Current Roaming Status = Home
Network Selection Mode = Automatic
Network = Verizon Wireless
Mobile Country Code (MCC) = 311
Mobile Network Code (MNC) = 480
Packet switch domain(PS) state = Attached
Registration state(EMM) = Registered
EMM Sub State = Normal Service
Tracking Area Code (TAC) = 49163
Cell ID = 49191425

[johnlloyd_13]

hi,

your RSSI (-56 dBm) looks good and RAT indicated it's getting LTE.

let us know if the given commands made any difference.

you might want to run some debugs in order to know why your connectivity is bouncing:

debug chat
debug modem
debug dialer
ebug cellular 0 messages callcontrol

[Njordic1429]

Will do thanks!

[Tagir Temirgaliyev]

I think

ip route 0.0.0.0 0.0.0.0 Cellular0  permanent

[Philip D'Ath]

If it is the only outbound interface on the router that that would be a good option.

[Njordic1429]

Yes it's the only outbound interface.