I have an exp-e with dual NIC setup. NIC1 is internal and NIC2 is external. NIC2 is on a DMZ and it uses an RFC1918 IP so I have defined the static NAT public IP for NIC2. The exp-e uses an FTD firewall on NIC2 as it's default gateway and I have a static route to an internal subnet using NIC1. The exp-e is used for MRA phones and Webex clients and as long as the phones and clients are coming from the public Internet all is good. Managing the box and connection to exp-c works fine using NIC1.
The problem I have is with an internal/private guest subnet that is connected to the same physcial firewall as NIC2 but on a different FTD interface. To route to this subnet the exp-e uses the same gateway but then the FTD routes it out it's guest subnet interface rather than it's outside interface. TCP and ICMP traffic look good. I can ping to/from the exp-e and the guest subnet. Webex clients can register and make calls. Checking the FTD logs I see that all the traffic types tcp, udp and ICMP are hitting the correct fastpath (prefilter) rules and being allowed thru the FTD. I also see them using the correct FTD interfaces and IPs.
However, the Webex clients on the guest subnet are getting one way audio. They can hear callers but caller can't hear them. In the FTD logs I can see many instances of either the webex client or the exp-e sending UDP packets but zero returning which I guess explains the audio issues. From the logs it would seem all audio should be having issues but somehow it's only inbound to the Webex clients.
I suspect a routing or NAT issue but why would it be affecting only UDP traffic? Maybe the exp-e is trying to use it's defined public IP for the guest subnet? If so, how can I address this?
Thanks,
Diego
