There are two ways to accomplish this goal with the 10G-PCIE2-8C2-2* and 10G-PCIE2-8B2-2* adapters.
First, you can load Sniffer10G on the adapter, but only open one port for sniffing. An Ethernet port remains usable as a regular ethernet device until (and if ever) it is opened for sniffing (Sniffer mode). So if only snf0 is ever opened, the myri1 ether device remains usable. Similarly, as soon as snf0 is closed for sniffing, the myri0 ethernet device is again usable if it has previously been brought up with ifconfig. Both myri0 and myri1 can be configured (or not) as ethernet devices at any time -- the only difference is that Sniffer will usurp the ethernet traffic from the regular driver path when snf0 (or snf1) is opened for Sniffing (either through pcap or the API).
The second option, if performance is important, is to use the Myri10GE driver that has performance extensions, rather than the functional Ethernet driver bundled with myri_snf. If this case, you should use the myri_bus or myri_mac driver options (i.e., load-time module parameters) to specify on which port of the adapter to load the Sniffer10G driver and on which port to load the Myri10GE 10G Ethernet driver.
Refer to How do I select on which network adapter ports the Sniffer10G driver is loaded? for more details on using the Sniffer10G load-time parameters myri_bus and myri_mac.
