Cisco 881 4g connection

[Noel Healy]

Hi Folks, I have a 881 router configured to use for 4g access. It is normally good, but often, when the 4g connection drops due to no been in use, etc, it can be very slow to reconnect. Often the only way to reconnect the 4g connection is reboot the router is needed. and event the, it does not alway come back up easily. You can often see lots and lots of attempts in the logs to connect, but it fails. I though it was a provider issue, but I see the same issue with 2 different provider. Attaching some logs to help show the dropped attempts.

Attaching logs and config for convenience

[Giuseppe Larosa]

Hello @Noel Healy ,

given the log lines

Mar 30 19:40:34.088: %LINEPROTO-5-UPDOWN: Line protocol on Interface Cellular0, changed state to up
Mar 30 19:47:17.595: TTY10: timer type 1 expired
Mar 30 19:47:17.595: TTY10: Exec-timeout expired
Mar 30 19:47:17.595: TTY10: destroy timer type 1
Mar 30 19:47:17.595: TTY10: Line reset by "SSH Process"
Mar 30 19:47:17.595: TTY10: Modem: (unknown)->READY
Mar 30 19:47:17.595: TTY10: no timer type 0 to destroy
Mar 30 19:47:17.595: TTY10: no timer type 1 to destroy
Mar 30 19:47:17.595: TTY10: no timer type 3 to destroy
Mar 30 19:47:17.595: TTY10: no timer type 4 to destroy
Mar 30 19:47:17.595: TTY10: no timer type 10 to destroy
Mar 30 19:47:17.595: TTY10: no timer type 2 to destroy

and your configuration I would suggest the following:

from a PC that is allowed to go to the internet open a shell cmd and perform a ping to 8.8.8.8 all the time and see if the connection becomes stable.

use ping 8.8.8.8 -t on a windows PC.

I have noticed in the past that this "poor man" workaround helps because it keeps the connection active all the time with a minimal use of traffic.

Hope to help

Giuseppe

[Noel Healy]

Thank you Giuseppe, 

You brought up an interesting point. These logs are taken whilst a continuous ping is running...

I should have included this in the initial description. With continuous ping running on the router or from pc that is on the correct vlan with external access and that will trigger the dialer, the connection takes a very very long time (can be hours) to reconnect. So much so, its making the router unusable :(

I'm thinking there must be something incorrect in the configuration as I'm sure this is not normal behaviour

[Giuseppe Larosa]

Hello @Noel Healy ,

your configuration looks like correct.

To verify the chat script you may contact the mobile ISP as these scripts can change.

I agree that one hour is not acceptable to set up the connection. There is something to be fixed and likely it is in the chat script. Otherwise you may be hitting a SW bug.

Hope to help

Giuseppe

[Noel Healy]

Thanks Giuseppe

I was thinking along similar lines. This happens with two different ISP's/providers. 

I did double check the ISP requirements and APN for both and both have a very simple requirements, just APN and no authentication. 

I would also expect to see something in the logs about the connection being refused if the chat was wrong, bit I'm not an expert in chat scripts, so if there is any pointers for more debugging or chat script options to try please pass on.

When debugging I normally enable debug on 

chat

modem

diaper

cellular 0 message callcontrol

I may be missing something though so open to suggestions

[Giuseppe Larosa]

Hello @Noel Healy 

from the part number of your router the GA means Global Australia and it means the router is intended to be used outside USA.

see

https://www.cisco.com/c/en/us/products/collateral/routers/800-series-routers/datasheet_c78-732744.html

Your debug list is quite complete , if you really want to see the ICMP packets flow you can add

access-list 121 permit icmp host 10.10.10.10 host 8.8.8.8

access-list 121 permit icmp host 8.8.8.8 host 10.10.10.10

debug ip pack 121

This is just to verify that the ICMP packets flow are seen / processed by the router not only only the first packet that trigger dialer action.

With your dialer list definition each ping packet should reset the idle timeout so no timeouts should occur and using this trick of ping 8.8.8.8 -t you should be always connected to the base station.

Edit:

from your logs we can say you are in Ireland

https://en.wikipedia.org/wiki/Mobile_country_code

so the router LTE modem should be of the right type. ( mobile country code =272 )

Hope to help

Giuseppe

[Noel Healy]

Thank you Giuseppe, 

I like the idea of being able to add icmp to the debug to be able to see if resets the idle timeout, very smart thinking!

I did check the model some time ago, but your right to call it out as it would cause major problems if it were wrong. 

Thank you again, 

I have something to work with :)

[Georg Pauwen]

Hello,

on a side note, I am looking at some sample configs, you might want to try and add the lines marked in bold. Not sure if any of that makes a difference...

Current configuration : 2834 bytes
!
! Last configuration change at 20:13:26 UTC Mon Mar 30 2020 by netadmin
! NVRAM config last updated at 20:08:38 UTC Mon Mar 30 2020 by netadmin
!
version 15.4
service timestamps debug datetime msec
service timestamps log datetime msec
service password-encryption
!
hostname Router
!
boot-start-marker
boot system flash c800-universalk9-mz.SPA.154-3.M7.bin
boot-end-marker
!
no aaa new-model
!
ip dhcp excluded-address 192.168.1.1
ip dhcp excluded-address 192.168.1.100
!
ip dhcp pool LANPOOL
network 192.168.1.0 255.255.255.0
default-router 192.168.1.1
dns-server 8.8.8.8 8.8.4.4
!
ip domain name healylabs.loc
ip name-server 8.8.8.8
ip name-server 8.8.4.4
ip cef
no ipv6 cef
!
multilink bundle-name authenticated
!
chat-script lte "" "AT!CALL" TIMEOUT 20 "OK"
!
cts logging verbose
license udi pid C881G-4G-GA-K9 sn FCZ204*****
!
username ******* privilege 15 secret 5 *****************
!
controller Cellular 0
lte sim primary slot 1
--> lte sim data-profile 1 attach-profile 1 slot 1
lte modem link-recovery rssi onset-threshold -110
lte modem link-recovery monitor-timer 20
lte modem link-recovery wait-timer 10
lte modem link-recovery debounce-count 6
!
interface Cellular0
ip address negotiated
ip nat outside
ip virtual-reassembly in
encapsulation slip
dialer in-band
--> dialer idle-timeout 0
dialer string lte
dialer-group 1
--> async node interactive
!
interface FastEthernet0
no ip address
!
interface FastEthernet1
no ip address
!
interface FastEthernet2
no ip address
!
interface FastEthernet3
no ip address
!
interface FastEthernet4
no ip address
duplex auto
speed auto
!
interface Vlan1
ip address 192.168.1.1 255.255.255.0
ip nat inside
ip virtual-reassembly in
!
ip forward-protocol nd
no ip http server
no ip http secure-server
!
ip nat inside source list NAT interface Cellular0 overload
ip route 0.0.0.0 0.0.0.0 Cellular0
ip route 10.10.8.0 255.255.255.0 192.168.1.100
ip route 10.10.9.0 255.255.255.0 192.168.1.100
ip route 10.10.10.0 255.255.255.0 192.168.1.100
!
ip access-list extended NAT
permit ip 192.168.1.0 0.0.0.255 any
permit ip 10.10.10.0 0.0.0.255 any
!
dialer-list 1 protocol ip permit
!
control-plane
!
mgcp behavior rsip-range tgcp-only
mgcp behavior comedia-role none
mgcp behavior comedia-check-media-src disable
mgcp behavior comedia-sdp-force disable
!
mgcp profile default
!
line con 0
no modem enable
line aux 0
line 2
no activation-character
no exec
transport preferred none
transport input all
stopbits 1
line 3
exec-timeout 0 0
script dialer lte
--> login
modem InOut
no exec
rxspeed 100000000
txspeed 50000000
--> transport input all
line vty 0 4
access-class NAT in
exec-timeout 7 0
login local
transport input ssh
!
scheduler allocate 20000 1000
ntp master
ntp update-calendar
ntp server 1.ie.pool.ntp.org
ntp server 3.ie.pool.ntp.org
!
end

[Noel Healy]

Thank you Georg

I will add this configuration to the router and see if they help over time. 

Many thanks for taking the time to review and provide help.