SIP Gateway with failover to second ISP

[Mark Verwey]

Need to setup a gateway SIP router with 2 separate interfaces.  Interface 1 is the primary, if it goes down then the router switches the route and sends the calls out the second interface.  I am using a Cisco 2951 w/Cube license, a broadband connection for 1 connection (int g0/1) and a cradlepoint CB850 for the second interface.  I have the configuration for the primary interface to handle calls in and out.  I dont knwo how to configure the router to monitor this interface and switch to the alternate interface if the primary interface goes down then continue to monitor that interface and then switch back when it does come back online.  This is needed because we all know how stable a broadband connection is, and because this is a small branch office they dont need a big pipe to handle calls (only 3-4 people).

[Vaijanath Sonvane]

Hi,

I had a similar situation and I used backup interface feature of the router. You need to use this command on primary interface. Please see this post for more details:

https://community.cisco.com/t5/switching/backup-interface-command/td-p/772342 

Here is the configuration from my router:

interface GigabitEthernet0/0/0
 description interface - Primary
 backup interface GigabitEthernet0/0/1
 ip address 10.20.10.19 255.255.255.0
 no ip redirects
 negotiation auto
!
interface GigabitEthernet0/0/1
 description interface - Backup
 ip address 10.20.10.19 255.255.255.0
 negotiation auto
!

[Anthony Holloway]

How would they handle their SIP binds in this configuration? I can see how a NAT + SIP ALG would work here, but otherwise, I'm not able to visualize how it would work.

[Vaijanath Sonvane]

Hi Anthony,

In my case, I have these two interfaces connected to two different switches and all my calls were going to same ITSP. So I have below configuration on my CUBE router:

interface GigabitEthernet0/0/0
 description interface - Primary
 backup interface GigabitEthernet0/0/1
 ip address 10.20.10.19 255.255.255.0
 no ip redirects
 negotiation auto
!
interface GigabitEthernet0/0/1
 description interface - Backup
 ip address 10.20.10.19 255.255.255.0
 negotiation auto
!
dial-peer voice 91 voip
preference 1
description *** DIAL PEER FOR OUTGOING PSTN CALLS ***
translation-profile outgoing SIP_OUT_DIGITSTRIP_9
destination-pattern 9T
session protocol sipv2
session target ipv4:12.13.15.16
voice-class codec 1
voice-class sip early-offer forced
voice-class sip bind control source-interface GigabitEthernet0/0/0
voice-class sip bind media source-interface GigabitEthernet0/0/0
dtmf-relay rtp-nte
no vad
!
dial-peer voice 92 voip
preference 2
description *** DIAL PEER FOR OUTGOING PSTN CALLS ***
translation-profile outgoing SIP_OUT_DIGITSTRIP_9
destination-pattern 9T
session protocol sipv2
session target ipv4:12.13.15.16
voice-class codec 1
voice-class sip early-offer forced
voice-class sip bind control source-interface GigabitEthernet0/0/1
voice-class sip bind media source-interface GigabitEthernet0/0/1
dtmf-relay rtp-nte
no vad
!

[Mark Verwey]

For the moment I have a solution working in my lab.  On GB interface0/0 I connect to the same network as my PBX is on.  GB interface0/1 I have the broadband facing network.  In the voice services voip/sip I have the bind statement pointing to the gb interface 0/1.  Under the SIP-UA I have the registration information for the carrier. Between GB interface 0/1 and the BB I have placed a Cradlepoint.  The cradlepoint is configued to send a ping every 30 seconds to google's DNS server.  If it fails it then redirects the calls out its 4G interface and continues to monitor the primary interface to get to the DNS server of google.  

Someone suggested that instead of sending all traffic out 1 interface and having the cradlepoint do the routing out, but put the BB on 1 interface and the cradlepoint on another interface.  Then create tunnels and let EIGRP be the traffic cop to monitor the BB interface and redirect traffic out the cradlepoint interface when the BB interface goes down.  I think this would be a great solution if all I was doing was sending and receiving data, however this isnt the case. There are several problems 1 being the binding statements.  Not to mention I dont have a clue how to create the tunnels and use EIGRP. 

Anyone have an idea how this could be possible?

[packetdictator]

the solution on this is eem scripts

track the sip providers ip address on the primary interface

aguments

disable the interface if the sip provider is down to force the router to the second interface

cheers