This is an update to a now closed thread (forums.untangle.com/networking/20077-eigrp-issue.html).
After much wrangling and reconfiguring the Cisco routers & ASA to use static routing, we still had no connectivity except to the inside interface. Turns out ESXi's virtual switch was the holdup. The traffic entering Untangle was all VLan tagged (not vlan1) and the ASA (attached directly to the external interface) couldn't be 'seen' properly. After some digging, I found an old thread on this forum that proposed the problem could be with VMWare's virtual switching. Yes, the same ESXi/Untangle setup had been functioning perfectly in the previous environment using Watchguard as the firewall.
The whole reason Untangle (ver 7 at the time) was originally loaded under ESXi was because Debian didn't yet support the Intel Pro1000 dual NICs present on HP DL160 G6. With the release of Untangle 9, that hardware is now natively supported... and works 100% 'out of the box'.
Despite a few quirks, I'd just like to say how incredible Untangle is! Keep up the good work, folks.