Failover SIP or H323 Trunk based on ISDN Status on Voice Gateways

[Mohammed al Baqari]

This is one of the common requirements to failover SIP trunk or H323 trunk if ISDN status is down. The following configuration will shutdown SIP/H323 service on voice gateway once ISDN status changes to down. Also, it will start SIP/H323 services once the ISDN status changes to UP

Note that you need to change the interface (marked in red) based on your controller type (E1/T1) and controller number (0/0/0 or 0/0/01 etc). Also, this configuration is for SIP trunk but can be applied to H323 by changing the protocol marked in red.

event manager applet SHUTDOWN_SIP
 event syslog pattern "Line protocol on Interface Serial0/0/0:15, changed state to down" period 1
 action 1.0 cli command "enable"
 action 1.1 cli command "config t"
 action 1.2 cli command "voice service voip"
 action 1.3 cli command "sip"
 action 1.4 cli command "call service stop forced"
 action 1.5 syslog msg "SIP Services Brought Down by EEM"

event manager applet BRING_UP_SIP
 event syslog pattern "Line protocol on Interface Serial0/0/0:15, changed state to up" period 1
 action 1.0 cli command "enable"
 action 1.1 cli command "config t"
 action 1.2 cli command "voice service voip"
 action 1.3 cli command "sip"
 action 1.4 cli command "no call service stop"
 action 1.5 syslog msg "SIP Services Brought Up by EEM"

[Ayodeji Okanlawon]

Mohammed,

Good document. We could easily just use cucm service parameter (stop routing on un allocated number) to do this. But its a good way to demonstrate the power of using EEM.

[Mohammed al Baqari]

Ayodeji,

Thx for your comment. The problem with this service parameter that it will failover if a user dials wrong number. PRI gateway will send 'Unallocated number' message to cucm on wrongly dialed numbers. 

I feel it is excessive to failover on wrongly dialed numbers

Using EEM is more accurate to track isdn status.

[Ayodeji Okanlawon]

That is a fair point but is it not too excessive to shut down sip service or h323 service globally because an ISDN interface goes down? What if I have other services using the gateway?

[Mohammed al Baqari]

That is the point of failover.  The second gateway should be capable of serving all services. 

[Ayodeji Okanlawon]

Ok so this is assuming I have two gateways. What if I have a single gateway with multiple ISDN connectivity...I guess this will be more effective in the event that we have more than one gateway.

[Mohammed al Baqari]

In this case it will make more sense to dialpeer hunting instead of relying on cucm. This will avoid duplicate configs when using srst with cucm.

I am not trying to debate. I am trying to share my thoughts and experience. 

[Ayodeji Okanlawon]

Hi Mohammed, 

I am not trying to debate either. Sorry if you got that impression. I am just weighing the pros and cons. 

Thanks for sharing your ideas 

[Mohammed al Baqari]

Thx Sir. On the other hand I have to say that u r doing great in the forum. Keep it up mate :)

[Steven Luton]

I can't get this to work.  I have a 4321 device running Version 03.16.00c.S.  I've tried the exact wording and changed only the interface number and it isn't working.  I've also tried changing the syslog pattern to match what actually shows up in the log when I shut down the controller.

[Dmitriy Michshuk]

no dial-peer outbound status-check pots