netgraph with 10Gig interfaces

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I cannot get netgraph to work with 10Gig interfaces
on FreeBSD 6.1.  No errors, but no traffic seen.
Config works with 1 Gig interfaces.  Anyone know why?

ngctl mkpeer . eiface hook ether
ngctl mkpeer ngeth0: one2many lower one
ngctl connect $if1: ngeth0:lower lower many0
ngctl connect $if2: ngeth0:lower lower many1
ifconfig ngeth0 -arp up

Thanks.