So I've been working on a project to implement 3g failover in case of a downed T1. I have code that works but the solution just seems horribly overcomplicated. I'm honestly a little embarrassed to post this as it just looks ugly, but it does appear to be working as intended. Am I on the right track here or is there an easier and/or more reliable way to do this? Comments and explanation are in the code.
ip route <Backup DMVPN hub> 255.255.255.255 Cellular0/0/0
ip route <Primary DMVPN hub> 255.255.255.255 <T1 gateway>
ip sla 1 // Ping primary DMVPN hub out T1 interface every 2 seconds, timeout ping after 1 sec
icmp-echo <Primary DMVPN hub> source-interface GigabitEthernet0/0
threshold 1000
timeout 1000
frequency 2
ip sla schedule 1 life forever start-time now
track 1 ip sla 1 reachability // Wait for 4 consecutive failed or successful pings to mitigate unnecessary flapping
delay down 9 up 9
track 2 interface Cellular0/0/0 line-protocol
track 3 interface Cellular0/0/0 ip routing
track 4 list boolean and // If I can't ping primary hub, cell does not have an IP address, and cell is ready to dial.
object 1 not // Had to add this track since failover would not work from cold boot if T1 was down, because
object 2 // tracking relies on a state change.
object 3 not
delay down 5 up 5
event manager applet SHUTS_TUNNEL1 // Closes tunnel to backup DMVPN and reset cell to kill call
event track 1 state up
action 10 cli command "enable"
action 20 cli command "config t"
action 30 cli command "interface Tunnel1"
action 40 cli command "shut"
action 5 syslog msg "SHUTS_TUNNEL1"
action 50 cli command "clear interface Cellular0/0/0"
action 70 cli command "end"
event manager applet NO_SHUTS_TUNNEL1 // Opens tunnel to backup DMVPN hub and creates interesting traffic to kick off dial
event track 1 state down
action 10 cli command "enable"
action 20 cli command "config t"
action 30 cli command "interface Tunnel1"
action 40 cli command "no shut"
action 5 syslog msg "NO_SHUTS_TUNNEL1"
action 50 cli command "clear interface Cellular0/0/0"
action 70 cli command "end"
action 80 cli command "ping <DMVPN backup hub> repeat 20"
event manager applet INIT_CELL // Duplicate of above code because applets apparently can't follow more than 1 track (AFAIK)
event track 4 state up
action 10 cli command "enable"
action 20 cli command "config t"
action 30 cli command "interface Tunnel1"
action 40 cli command "no shut"
action 5 syslog msg "INIT_CELL"
action 50 cli command "clear interface Cellular0/0/0"
action 70 cli command "end"
action 80 cli command "ping <DMVPN backup hub> repeat 20"
