can we use 2 interfaces for CME for cisco 2921?

[kenny hon]

Dear All,

I am new on cisco product.

Currently, we have conflict voip subnet mask for our vpn site. In order to solve this problem, we have added 1 for interface in cisco 2921 for CME. It got the problem now is we can call each other but no voice. I want to ask if is it only the sip trunk setting issue? or is it cisco 2921 don't support 2 interface for CME?

Looking forward your answer.

Kenny

[kenny hon]

Dear All,

I just want to clarify the questions i asked here. The cisco 2921 have been installed CME is working for 1st interface with our subnet mask 192.168.20.x/24. However, we got another vpn site have the same subnet mask for voip. In order to avoid the ip conflict, we want to use 2nd interface in cisco 2921( eg. 200.200.0.0/24) to connect to our conflict ip site. Right now, vpn is connected and we can dial each other with tones but no voice. I want to know if cisco 2921 support 2 interface for CME?

Thank you.

Kenny

[paolo bevilacqua]

Yes. However, you cannot have sites using the same address, no matter how you connect them.

[kenny hon]

Dear Paolo,

Thank you answer.

Do you mean that we can have 2 interface for CME. Eg our case

0/0 interface 192.168.20.10 is for China site

i) we will use 192.168.20.0/24 for vpn link between china site and our site.

0/1 interface 200.200.0.10 is for Thailand site

i) we will use 200.200.0.0/24 for vpn link between Thailand site and our site.

Our 1st interface work fine now. but the 2nd interface don't work.

Is it any special setting for 2nd interface?

Thanks

Kenny

[kenny hon]

Dear All,

From Paolo reply, is it it support 2 interface for CME or not?

Thanks

Kenny

[ronpatel]

Hi Kenny,

For CME one router can be configured for only one source interface. The secondary ip address in source interface command is used when your primary cme router is down.

Regards

Ronak Patel

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[kenny hon]

Dear Ronak,

Thanks your reply

If only one source interface can be used for CME in 2921 router. Beside the change subnet for our CME, do you have any solution if our other site voip subnet is the same as our voip subnet? 

Thanks.

Kenny

[paolo bevilacqua]

Ronak refers to only one 'ip source interface' command under telephony-service.

Then for connecting the phones, you can use as many phisical interfaces you desire, as stated before already.

[kenny hon]

Dear All,

As our case is there have a conflict subnet between our thailand and HK site. In HK, it have CME 192.168.20.10 and subnet is 192.168.20.0/24 while Thailand site, it have CM (192.168.20.100) and  the same subnet 192.168.20.0/24

Without changing the subnet, we would like to add another interface in our hk site such as 200.200.0.1 for the vpn link between thailand and hk site. We got the problems right now is when we dial a call, the source always is from 192.168.20.10 to 192.168.20.100, but there have no ack from 192.168.20.100. is the 2nd interface work between CME and CM using sip trunk?

Thanks

kenny

[ronpatel]

Hi Kenny,

Now I got clear picture what you want.

You will have to isolate the 2 networks using the CUBE as a router.. So one interface of CUBE will be on 1 network reachable by 1 side of the network and the other interface ( of CUBE ) will be on the other side of the network.. Something like this:

IP phones - A (10.1.1.X) ------ (20.1.1.X) CUBE (30.1.1.X) ------ IP phones

­ B (10.1.1.X)

The routes from 10.1.1.X Site A should be reachable to 20.1.1X only and from Site B to 30.1.1.X only... CUBE will take care of the IP address hiding of the IP phones at both ends.. IP phones at each end will never see the other end as they will be sending the media only to CUBE¹s IP address..

No other option without using CUBE.

Regards

Ronak Patel

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[kenny hon]

Dear Ronak,

Thanks for your answer. What is CUBE? and can you explain more. IP phones A(10.1.1.x) with call manager is 10.1.1.10

IP phones B (10.1.1.x) with call manager ip is 10.1.1.100

Thanks

Kenny

[ronpatel]

HI

CUBE is IPIP gateway.

http://www.cisco.com/en/US/products/sw/voicesw/ps5640/index.html

regards

Ronak Patel

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[paolo bevilacqua]

Ronak Patel wrote:
Hi Kenny,
Now I got clear picture what you want. 
You will have to isolate the 2 networks using the CUBE as a router.. So one interface of CUBE will be on 1 network reachable by 1 side of the network and the other interface ( of CUBE ) will be on the other side of the network.. Something like this:
IP phones - A (10.1.1.X) ------ (20.1.1.X) CUBE (30.1.1.X) ------ IP phones
­ B (10.1.1.X)
The routes from 10.1.1.X Site A should be reachable to 20.1.1X only and from Site B to 30.1.1.X only... CUBE will take care of the IP address hiding of the IP phones at both ends.. IP phones at each end will never see the other end as they will be sending the media only to CUBE¹s IP address..
No other option without using CUBE. 

No, CUBE cannot handle duplicate IP address/sbunet either. Only NAT can handle that, howver it introduce further complication, so the best solution is no simply renumber one site.

[ronpatel]

Hi

One of the function of CUBE is IP address hiding. So I think CUBE will resolve the issue.

http://www.networkworld.com/community/node/18048

Regards

Ronak patel

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[paolo bevilacqua]

Ronak Patel wrote:
Hi 
One of the function of CUBE is IP address hiding. So I think CUBE will resolve the issue. 
http://www.networkworld.com/community/node/18048
Regards
Ronak patel
rate helpful posts. 

The person that wrote that blog has little knowledge. Address hiding does not means handling duplicate address.

Once CUBE (or any router) sees the same subnet to reachable in multiple ways, will start sharing packets, but these will never reach the correct destination, and will not work. Try youself if you want first-hand proof.