7 VPN servers with high load have multiple kernel panics.
FreeBSD + MPD + quagga used

(kgdb) backtrace 
#0  doadump (textdump=Variable "textdump" is not available.
) at pcpu.h:224
#1  0xffffffff808ea3a1 in kern_reboot (howto=260) at /usr/src/sys/kern/kern_shutdown.c:448
#2  0xffffffff808ea897 in panic (fmt=0x1 <Address 0x1 out of bounds>) at /usr/src/sys/kern/kern_shutdown.c:636
#3  0xffffffff81633df8 in ng_iface_disconnect (hook=0x0) at /usr/src/sys/modules/netgraph/iface/../../../netgraph/ng_iface.c:821
#4  0xffffffff8162343e in ng_destroy_hook (hook=0xfffffe0129ba2600) at /usr/src/sys/modules/netgraph/netgraph/../../../netgraph/ng_base.c:1207
#5  0xffffffff81623da0 in ng_apply_item (node=0xfffffe00197d0100, item=0xfffffe012981e580, rw=1)
    at /usr/src/sys/modules/netgraph/netgraph/../../../netgraph/ng_base.c:2462
#6  0xffffffff81622efe in ng_snd_item (item=Variable "item" is not available.
) at /usr/src/sys/modules/netgraph/netgraph/../../../netgraph/ng_base.c:2308
#7  0xffffffff816233f2 in ng_destroy_hook (hook=0xfffffe002f062080) at /usr/src/sys/modules/netgraph/netgraph/../../../netgraph/ng_base.c:1182
#8  0xffffffff816238b9 in ng_rmnode (node=0xfffffe001970f000, dummy1=Variable "dummy1" is not available.
) at /usr/src/sys/modules/netgraph/netgraph/../../../netgraph/ng_base.c:735
#9  0xffffffff81624474 in ng_apply_item (node=0xfffffe001970f000, item=0xfffffe0129181980, rw=1)
    at /usr/src/sys/modules/netgraph/netgraph/../../../netgraph/ng_base.c:2511
#10 0xffffffff81622efe in ng_snd_item (item=Variable "item" is not available.
) at /usr/src/sys/modules/netgraph/netgraph/../../../netgraph/ng_base.c:2308
#11 0xffffffff816201c2 in ngc_send (so=Variable "so" is not available.
) at /usr/src/sys/modules/netgraph/socket/../../../netgraph/ng_socket.c:317
#12 0xffffffff80955ef6 in sosend_generic (so=0xfffffe007944ad48, addr=0xfffffe0009b179a0, uio=0xffffff81198a98c0, top=0xfffffe00173ac500, control=0x0, flags=Variable "flags" is not available.

) at /usr/src/sys/kern/uipc_socket.c:1307
#13 0xffffffff80959853 in kern_sendit (td=0xfffffe0013110000, s=5, mp=0xffffff81198a9990, flags=0, control=0x0, segflg=Variable "segflg" is not available.
)
    at /usr/src/sys/kern/uipc_syscalls.c:810
#14 0xffffffff80959aec in sendit (td=0xfffffe0013110000, s=5, mp=0xffffff81198a9990, flags=0) at /usr/src/sys/kern/uipc_syscalls.c:738
#15 0xffffffff80959bdd in sys_sendto (td=Variable "td" is not available.
) at /usr/src/sys/kern/uipc_syscalls.c:862
#16 0xffffffff80bd7ae6 in amd64_syscall (td=0xfffffe0013110000, traced=0) at subr_syscall.c:135
#17 0xffffffff80bc3447 in Xfast_syscall () at /usr/src/sys/amd64/amd64/exception.S:387
#18 0x000000080223e4ac in ?? ()
Previous frame inner to this frame (corrupt stack?)


(kgdb) up 3
#3  0xffffffff81633df8 in ng_iface_disconnect (hook=0x0) at /usr/src/sys/modules/netgraph/iface/../../../netgraph/ng_iface.c:821
821			panic("%s", __func__);

How-To-Repeat: Bug stable reproducing on our servers, can provide any additional info.