configuration of bonded pris between 2 CMEs

Unanswered Question
Aug 31st, 2008


I am relatively new to the voice arena and was hoping someone could shed some light on my issue.

We have ordered 2 bonded PRI circuits and would like to have one circuit in each of our CMEs. The DIDs are configured to go via the primary circuit and fail over the the secondary if the first should fail. Ultimately, we are looking for redundancy in our voice network. Is there any issues having these circuits split between two CMEs or does the circuits have to go into the same CME?

Is there any documentation that can provide some configuration guidance? I was unable to locate anything that specific.

Thank you.

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Marwan ALshawi Sun, 08/31/2008 - 22:06

u can make it over two CMEs

but u need this commad to be enabled

voice service voip

allow conntection h323 to h323


u need this calss to decrease the failover time

voice class h323 1

h225 timeout tcp establish 3

so within 3 second the call can failover

lets take this example

CME ip

port 0/1 got topstn if down will send the call to CME2

CME2 ip

port 1/1 pstn

dial-peer voice 9 pots

destination-patteren .T


voice-class h323 1

port 0/1

forward-digit all

the default prefrence is 0 so this will be the default outbound dial peer

we gonna make another dial-peer but gonna be VOIP point to CME2 IP and its prefrence 2 higher than the default

based on the calss we created above the call will wait 3 seconds if not establitioed gonna fail over to the voip dial-peer to send the call to CME2 on CME2 we gonna forward it through its pstn line

dial-peer voice 91 voip

destination-pattren .T

prefrence 2

seesion target ipv4: [cme2 ip]

on CME

dial-peer voice 99 pots

destination-pattrent .T

port 1/1

forwar digit all

and the same idea u cam do it from

CME2 to CM1

good luck

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roseeng69 Tue, 09/02/2008 - 08:38

Thank you so much for answering and providing me with the information! I have to try this when we obtain our circuits.

roseeng69 Tue, 09/02/2008 - 08:59


Could these circuits work as an overflow for the primary ckt?

For redundancy of the primary router, would I need to add any other commands in the routers to make it redundant on the hardware end as well? Would it just be adding the secondary ip address under telephony-service?

Would this also make these two routers fully redundant in case of any issues?

Thanks again,


Marwan ALshawi Tue, 09/02/2008 - 16:35

hi rose

thhis is from cisco srnd with a link have a look

Redundant Cisco Unified CME Router

A second Cisco Unified CME router can be configured to provide call-control services if the primary Cisco Unified CME router fails. The secondary Cisco Unified CME router takes over and provides services seamlessly until the primary router becomes operational again.

When a phone registers to the primary router, it receives a configuration file from the primary router. Along with other information, the configuration file contains the IP addresses of the primary and secondary Cisco Unified CME routers. The phone uses these addresses to initiate a keepalive (KA) message to each router. The phone sends a KA message after every KA interval (30 seconds by default) to the router with which it is registered and after every two KA intervals (60 seconds by default) to the other router. The KA interval can be adjusted with the keepalive command.

If the primary router fails, a phone will not receive an acknowledgment (ACK) to its KA message to the primary router. If the phone does not get an ACK from the primary router for three consecutive KAs, it registers with the secondary Cisco Unified CME router.

During the time that the phone is registered to the secondary router, it keeps sending a KA probe to the primary router to see if it has come back up, now every 60 seconds by default or two times the normal KA interval. After the primary Cisco Unified CME router is operating normally, the phone starts receiving ACKs for its probes. After the phone receives ACKs from the primary router for three consecutive probes, it switches back to the primary router and reregisters with it. The reregistration of phones with the primary router is also called rehoming.

The physical setup for redundant Cisco Unified CME routers is as follows. The FXO line from the PSTN is split using a splitter. From the splitter, one line goes to the primary Cisco Unified CME router and the other goes to the secondary Cisco Unified CME router. When a call comes in on the FXO line, it is presented to both the primary and secondary Cisco Unified CME routers. The primary router is configured by default to answer the call immediately. The secondary Cisco Unified CME router is configured to answer the call after three rings using the voice-port ring number 3 command. If the primary router is operational, it answers the call immediately and changes the call state so that the secondary router does not try to answer it. If the primary router is unavailable and does not answer the call, the secondary router sees the new call coming in and answers after three rings.

The secondary Cisco Unified CME router should be connected in some way on the LAN, either through the same switch or through another switch that may or may not be connected to the primary Cisco Unified CME router directly. As long as both routers and the phones are connected on the LAN with the appropriate configurations in place, the phones can register to whichever router is active.

Configure primary and secondary Cisco Unified CME routers identically, with the exception that the FXO voice port from the PSTN on the secondary router should be configured to answer after more rings than the primary router, as previously explained. The ip source-address command is used on both routers to specify the IP addresses of the primary and secondary routers.

good luck

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