Failover Link on HWIC-3G-HSPA Timing Out

[bytewize_ns]

Hi,

I have a HWIC-3G-HSPA setup as a SLA failover link in my 1941. All works fine and if the primary WAN interface goes down the 3G link comes up and all is good. But the cellular link times out and shuts down after about two days. I've set the dialer 'idle-timeout 0' setting and does not work.

I want this to stay up all the time for several reasons, ii've upgraded the latest firmware and tried everything i can think of..

Here is the cellular interface config

------------------------------

interface Cellular0/0/0
description Failover WAN Interface
ip address negotiated
ip access-group 100 in
no ip redirects
no ip unreachables
ip nat outside
ip virtual-reassembly in
encapsulation ppp
dialer in-band
dialer idle-timeout 0
dialer string gsm
dialer-group 1
async mode interactive
ppp authentication pap callin
ppp eap refuse
ppp chap refuse
ppp ms-chap refuse
ppp ms-chap-v2 refuse
ppp ipcp dns request

------------------------------

I also have set SLA thinking this would keep the link up by sending packets to Google DNS entrnally..

------------------------------

ip sla 1
icmp-echo 8.8.8.8 source-interface GigabitEthernet0/0
threshold 1000
timeout 1000
frequency 3
ip sla schedule 1 life forever start-time now
ip sla 2
icmp-echo 8.8.8.8 source-interface Cellular0/0/0
threshold 2000
timeout 2000
frequency 3
ip sla schedule 2 life forever start-time now
dialer-list 1 protocol ip permit

------------------------------

Modem Firmware Version = K2_0_7_53AAP C:/WS/F
Modem Firmware built = 03/06/13
Hardware Version = 1.0
International Mobile Subscriber Identity (IMSI) = X
International Mobile Equipment Identity (IMEI) = X
Integrated Circuit Card ID (ICCID) = X
Mobile Subscriber Integrated Services
Digital Network-Number (MSISDN) =
Factory Serial Number (FSN) = X
Modem Status = Online
Current Modem Temperature = 30 deg C, State = Normal
PRI SKU ID = 9992680, SKU Rev. = 1.1

-----------------------------------

If i shut and no shut the primary WAN interface it comes up and will stay up for about two days then goes down again. I have a static IP on the 3G connection as well so its not a provider / IP issue. And the signal strength is consistent and close to the tower

-----------------------------------

Radio Information
=================
Radio power mode = ON
Current Band = WCDMA 2100, Channel Number = 10663
Current RSSI = -87 dBm
Current ECIO = -0 dBm
Band Selected = Auto
Number of nearby cells = 1
Cell 1
Primary Scrambling Code = 0x1D3
RSCP = -80 dBm, ECIO = -13 dBm

---------------------------------------

What am i missing here? Can someone help me please!

Thanks :)

Adrian

[Philip D'Ath]

I have had issues like this before.  The below command will cause the interface to tear down if no traffic is received for 10 minutes (usually a sign that something has gone wrong).

interface Cellular 0/0/0
  dialer idle-timeout 600 inbound

Your SLA configuration is fundamentally floored, as it doesn't force the traffic out a particular interface.  If you want to use that approach use something like:

ip route 8.8.4.4 255.255.255.255 Cellular 0/0/0 permanent

ip sla 2
  icmp-echo 8.8.4.4 source-interface Cellular0/0/0
  threshold 2000
  timeout 2000
  frequency 3
ip sla schedule 2 life forever start-time now

I don't know your Gigabit0/0 configuration, but you should force route 8.8.8.8 out that to make SLA work property.

Personally, I prefer to use NTP to generate traffic for purposes like this.  This will cause a small amount of constant traffic to be generated.  As a bonus, your device will also have the correct time.

ip route <ntp-server-1> 255.255.255.255 <next hop1> permanent
ip route <ntp-server-2> 255.255.255.255 <next hop2> permanent
ntp server <ntp-server-1>
ntp server <ntp-server-1>

[bytewize_ns]

Thanks, this has worked perfectly.. Much appreciated :)