Long connect to Oracle 11g from KVM VM (proxmox4). Why?

Question

linux

Firework!
There is a fresh configuration from the Hypervisor on Proxmox 4 and several virtual machines on it:
frontends - debian linux 8 (apache, tomcat, glasfish ...)
backends - oracle linux 6.7 (oracle db 12g)
all VMs are raised on KVM, they work without any complaints. Frontends and backends are wrapped, each in its own VLAN and in its own network. Transparent routing is configured between networks, that is, there are no restrictions on the passage of traffic between them.
The essence of the problem is that if you connect to the database from the frontend, then the connection can last up to 8 minutes, although there are times when it connects instantly. Moreover, if you connect from a physical machine, or from a VM on another hypervisor, then the connection always occurs within 3 seconds.
Tell me, dear experts, what this problem can be connected with, and how can I get around it

Answer 1

after much torment, it turned out that the problem is in the processor, which does not support a number of instructions necessary for full-fledged virtualization.

Answer 2

The name of the applicant is not trying to resolve the machine at that moment?
Delay to try to resolve the backresolve and then connect.
Well, the first thing that came to mind.

Answer 3

And from the console if you connect with the same telnet