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Cisco Employee
Cisco Employee

I have an engineer who's requiring me to assign a NAT inside address to a CUCM. Eth0 on this CUCM has been configured to a drop for outside access.

I am trying to configure the NAT to eth1 but it does not appear within the CUCM. It is enabled in BIOS and the lights are on on both ports.

How can I configure the NAT to eth1 if CUCM does not show the port? What am I doing wrong?

Any help is welcome. Thanks in advanced!

5 Replies 5

Jonathan Schulenberg
Hall of Fame
Hall of Fame

You cannot configure the Ethernet ports separately. Most of the VOS-model products only allow you to configure the secondary NIC into an active/standby failover configuration using the command set network failover.

Additionally, NAT typically mixes very poorly with voice since nearly all of the protocols involved (SCCP, SIP, H323, SDP, etc) contain IP addresses within the Layer 7 payload. Any NAT device would have to be capable of rewriting all of the protocols in use. Even the ASA has a buggy record at this due to revisions in the voice protocol that the firewall doesn't understand. You'll save yourself weeks worth of work by saying 'no' here.

Please remember to rate helpful responses and identify helpful or correct answers.

Thanks Jonathan! You saved me a big headache with this issue. Had already been working on it for about a week before realizing it was not an easy task. Thanks for clarifying.

Hello Jonathan,

I was told by the engineer that the CUCM had been configured before to have an IP for outside access plus a NAT IP onto the same CUCM. I have not found anything online that states this. Is there any way to do this?

Thanks a bunch!



No, the interfaces cannot be configured independently, all you can use the second NIC for, is redundancy.



if this helps, please rate



if this helps, please rate

Thanks Jaime, This did help. I also found it in the command line reference guide that you cannot configure Ethernet 1 port. Engineer claims two IP's were configured on this CUCM before but I do not see how that is possible.

He claims Outside IP and NAT were configured simultanously.

Thanks to you both.