Multi Cell / Multi Wan EEM/IP SLA Tracking

[Joseph Sullivan]

Looking for a way to setup a multi test approach for WAN/Internet Connections.  Cisco 2921 ISR

Cell 0/2/0 - ATT

Cell 0/3/0 - VZW

Gig 0/0/0 - Lan

Gig 0/1/0 - Satellite

Gig 0/2/0 - Terrestrial (Fiber, DSL, Cable, etc)

This router sits in an emergency response vehicle.  As the vehicle gets deployed in different areas it will have varying cell conditions and internet connections available to it.

With the Dual cell, I would like to setup a script that does the following.

Check Cell Signal on both carriers, pick the strongest signal. Proceed to Track/IP SLA.

Ping sourcing from interface, if line is up use route.  If down, test other cell interface with lower signal, if up, use route.

EEM, accept sms commands, restrict to phone numbers on approved list.  Text command “switch” to router, it will swap active cell connections, and reply with Current Cell status, and new cell status.

EEM, Text “Status” to router and respond with both current cell status and which is active.

If The terrestrial or Satellite connections are active, it will always use those over cell.  Satellite will always have a UP/UP status as it is connected to the satellite modem, terrestrial will always be down unless connected to a connection.  Terrestrial always trumps satellite.

Can someone help me write this?  

[Dan Frey]

Most of the requirements looks like a routing decision.   Have an IPSLA preconfigured for all 4 transports then go down the list.

• Use terrestrial if IPSLA 1 is up
• Use satellite if IPSLA 2 is up
• Look at IPSLA (3 and 4) of both wireless carriers.  
• If both are up, pick highest RSSI signal and set default static route to interface.   
• If one is up use it.
• If both IPSLA are down - out of service

- See this link for issuing commands over SMS.  Instead of Status command issue survey.   Can also issue show command and get the return value, and issue IOS configuration commands.

https://supportforums.cisco.com/document/12316801/commands-over-sms

[Joseph Sullivan]

Thanks Daniel, 

This makes sense to me.  On the last wish on my list, can I have EEM switch the two cell carriers if I want them to via sms?

Cheers!

[Dan Frey · Accepted solution]

EEM policy "commandoversms.tcl" in the above link can switch the cell carriers.   SMS the router cli commands needed to make the switch.   If your not tunneling the traffic then switching carriers can be destructive to connection oriented protocols.   The wireless carrier will want all traffic sourced from the IP address of the associated cellular interface and if your not tunneling then NAT will have to be provisioned.   When switching carriers the NAT table will have to be cleared and new connections initiated.

To simplify the policy I am assuming the static default routes have tracking statements and associated admin distance in the current running configuration.

Ip route 0.0.0.0 0.0.0.0 Terrestrial-next-hop-ip track 1

Ip route 0.0.0.0 0.0.0.0 sat-next-hop-ip 10 track 2

Ip route 0.0.0.0 0.0.0.0 cellular 0/3/0 20 track 3

Ip route 0.0.0.0 0.0.0.0 cellular 0/2/0 30 track 4

Default routing prefers VZW over ATT wireless using the static routes above.   When ATT has a better signal the EEM policy below will place an admin distrance of 15 to the ATT interface.   Likewise if current routing is using the ATT interface and VZW has a better signal EEM will make the ATT admin distance 30.  

event manager applet dual_cell
 event timer watchdog time 3600 maxrun 60
 action 010 cli command "enable"
 action 020 cli command "show cellular 0/2/0 radio | inc RSSI"
 action 030 set attsignal "$_cli_result"
 action 040 cli command "show cellular 0/3/0 radio | inc RSSI"
 action 050 set vzwsignal "$_cli_result"
 action 060 cli command "show ip route | inc 0.0.0.0"
 action 070 regexp "(Cellular[0-9\/]+)" "$_cli_result" match currentinterface
 action 080 if $_regexp_result eq "1"
 action 090  regexp "RSSI = (-[0-9]+) dBm" "$attsignal" match attsignal
 action 100  regexp "RSSI = (-[0-9]+) dBm" "$vzwsignal" match vzwsignal
 action 110  if $vzwsignal gt "$attsignal"
 action 120   if $currentinterface eq "Cellular0/2/0"
 action 130    cli command "config terminal"
 action 140    cli command "ip route 0.0.0.0 0.0.0.0 Cellular 0/2/0 30 track 4"
 action 150    cli command "do clear ip nat tr *"
 action 160   end
 action 170  elseif $attsignal gt $vzwsignal
 action 180   if $currentinterface eq "Cellular0/3/0"
 action 190    cli command "config terminal"
 action 200    cli command "ip route 0.0.0.0 0.0.0.0 Cellular 0/2/0 15 track 4"
 action 210    cli command "do clear ip nat tr *"
 action 220   end
 action 230  end
 action 240 end

[steven.anthony]

Good Morning.

Hoping someone here can help..

We've recently received a new version of the Cisco 819 Router.

IOS Version: c800-universalk9-mz.SPA.156-3.M0a.bin

Hardware: C819G-LTE-MNA-K9 (revision 6.0)

Running the commandoversms.tcl script crashes this router... I've tried it on several of them.. No matter what sms text I send to the device, it immediately crashes and reboots..

Has anyone else had this experience or heard of this?

Is this script not for use on this specific platform, as it worked with our former devices:

C819G-4G-A-K9

c800-universalk9-mz.SPA.154-3.M6a.bin

Thanks in advance!

[charles.ponton]

Im using the script with 15.6(3)M3a. No crashing issues

[steven.anthony]

I have no way to find my way back to this forum, except for this email....



We found out that if you have SMS archive configured on the Cisco 819, that was causing the crash.

C819G-LTE-MNA-K9

Also we needed a IOS upgrade since the IOS c800-universalk9-mz.SPA.156-3.M0a.bin has a SMS bug.

When a new SMS is received, it is not logging that activity, which is needed to kick off the commandoversms script..