VOICE GATEWAYS AND PRIS

[chrysostomos1980]

Hi to all

We have two gateways with one pri in each gateway.The two gateways are in two different locations and the first gateway is the main and the second is the backup

our questions are:

1) if you know the isp can recognise (with d channel) if the pri is down?

2) how the cucm (is connected with gw via h323) can recognize that the first pri is down (the gw is up but the pri is down) and then send the calls (outside calls) to the second Gateway

Regards

[Gajanan Pande]

Please find my Answers in-line below..

1) if you know the isp can recognise (with d channel) if the pri is down?

Ans : Yes. ISP would stop sending calls over that line/trunk untill they receive proper acknowledgement signalling from the gateway router's PRI D channel. Callers would hear busy tone.

2) how the cucm (is connected with gw via h323) can recognize that the first pri is down (the gw is up but the pri is down) and then send the calls (outside calls) to the second Gateway

Ans : This can be achieved using proper config of Route List >> Route Group >> Add gateways with priorities defined. So that, if the preferred gateway is down ( for whatever reason ), CUCM looks for next gateway as defined by priority.

HTH ?

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GP.

[chrysostomos1980]

Hi and thank you for the reply

for the second point we have created a route group that we have assigned first the main GW and second the backup GW with Distribution Algorithm "top down"

I think is the same that you mentioned before..BUT i believe that the CUCM can change and route the calls (outgoing calls) to the backup GW if the GW is down and not if the pri is down ...

Do you have any guide  for that?

[Gajanan Pande]

Yes, you are right if the gateway is H.323 ( I just forgot to notice that you already mentioned as H.323 gateway, sorry about that ). My above statement holds true for MGCP gateways.

My thought about achieving it with H.323 gateway would be to have a VOIP dialpeer on main gateway pointing to second gateway in case the PRI fails on main gateway.

Call flow would be CUCM >> Main H.323 Gateway >>  it finds the PRI to be down >> Call follows the dial-peer pointing towards second H.323 gateway >> Second gateway routes it to PSTN.

GP.

[acampbell]

Hi,

You will have to add the following line of text to the H323 gateways.

!

no dial-peer outbound status-check pots

!

This will ensure that a no circuit/channel available message - cause code 34

is sent back to CUCM so that it can step on the next GW in the route group.

Please see

https://www.cisco.com/en/US/docs/ios/12_3t/voice/command/reference/vrht_d1_ps5207_TSD_Products_Command_Reference_Chapter.html#wp1459139

Regards

Alex

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[chrysostomos1980]

Hi to alex , thank you for the update

could you pls alex and gajanan confirm that the below config is correct?

MAIN CUCM:10.1.1.1
MAIN GW:10.1.1.6
BACKUP GW:10.1.1.7
EXTENSIONS ARE: 1XXX

On the main GW

no dial-peer outbound status-check pots
!
dial-peer voice 100 voip
description **TO THE MAIN CUCM**
translation-profile outgoing ADD9
preference 1
destination-pattern ....
session target ipv4:10.1.1.1
voice-class codec 2 
voice-class h323 1
dtmf-relay h245-alphanumeric
no vad
!

dial-peer voice 300 voip
description **TO SECOND GW**
preference 2
destination-pattern ....
incoming called-number ....
session target ipv4:10.1.1.7
voice-class codec 2 
voice-class h323 1
dtmf-relay h245-alphanumeric
no vad
!

ON THE SECOND GW

no dial-peer outbound status-check pots
!
dial-peer voice 100 voip
description **TO THE MAIN CUCM**
translation-profile outgoing ADD9
preference 1
destination-pattern ....
session target ipv4:10.1.1.1
voice-class codec 2 
voice-class h323 1
dtmf-relay h245-alphanumeric
no vad
!

dial-peer voice 300 voip
description **TO THE MAIN GW**
preference 2
destination-pattern ....
incoming called-number ....
session target ipv4:10.1.1.6
voice-class codec 2 
voice-class h323 1
dtmf-relay h245-alphanumeric
no vad
!

[acampbell]

Hi,

I take it you have added the POTS dial peers for the outgoing calls

Regards

Alex

[chrysostomos1980]

If you mean the dial peer pots for the pstn network yes i have added these pots

i forgot also something

the main GW has two pris and the second GW one pri

So far are you believe that the config is correct between GW to GW?

Is anything change now that we have two pris to the main GW?

dial-peer voice 1 pots

description **CYTA FIRST Pri **

destination-pattern 9T

progress_ind alert enable 8

incoming called-number ....

direct-inward-dial

port 0/0/0:15

!

dial-peer voice 2 pots

description **CYTA SECOND Pri **

preference 10

destination-pattern 9T

progress_ind alert enable 8

incoming called-number ....

direct-inward-dial

port 0/0/1:15

dial-peer voice 1 pots

description **FIRST Pri **

destination-pattern 9T

progress_ind alert enable 8

incoming called-number ....

direct-inward-dial

port 0/0/0:15

!

dial-peer voice 2 pots

description **SECOND Pri **

preference 10

destination-pattern 9T

progress_ind alert enable 8

incoming called-number ....

direct-inward-dial

port 0/0/1:15

[acampbell]

Hi,

Yes these look OK.

Remember if your router has more than 1 IP address to bind 1 of them as the H323 source

Could be

!

int loop 1

ip add 10.10.10.10 255.255.255.255

h323-gateway voip bind srcaddr 10.10.10.10

!

HTH

Alex

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[chrysostomos1980]

thanks alex

the command no dial-peer outbound status-check pots is for mgcp gateway and not h323 right?

[acampbell]

Hi,

No it is for H323 & SIP gateways

Regards

Alex

[chrysostomos1980]

Thank you guys for the answers

Let me to test it and before give you the correct answer in case that its not working to give you un update for your records

Otherwise i will back here to confirm that everything its ok

Thank you again