Имеем:
железо: Intel S5000VSL
ОС: FreeBSD 7.1-PRERELEASE #2: Thu Dec 10 14:57:45 MSK 2009

При ~110k записей всё хорошо, достигаем ~125-140к начинаются ошибки на сет. интерфейсе, чистим трансляции - ошибки исчезают.

# ipnat -s
mapped  in      285037401       out     221990930
added   11096611        expired 10218253
no memory       0       bad nat 235943
inuse   129092
orphans 0
rules   9
wilds   1
hash efficiency 12.69%
bucket usage    99.97%
minimal length  0
maximal length  22
average length  7.882
TCP Entries per state
     0     1     2     3     4     5     6     7     8     9    10    11
    88  4735   157  2626  7079   345    65    17    36     0 43362  1505

# netstat -I em0 -w 1
            input          (em0)           output
   packets  errs      bytes    packets  errs      bytes colls
      6306   541    6300808       5877     0    1242162     0
      6736   416    6535743       6276     0    1309721     0
      7738   514    8288666       6523     0    1405937     0
      7630   462    7551297       6721     0    1556890     0
      5207   443    4997805       4952     0    1248456     0

# ipnat -CF -f /etc/ipnat.rules
128944 entries flushed from NAT table
9 entries flushed from NAT list

# netstat -I em0 -w 1
            input          (em0)           output
   packets  errs      bytes    packets  errs      bytes colls
      3205     0    2584267       3132     0     650453     0
      4704     0    4305612       4352     0     813504     0
      4463     0    3898817       4223     0     856430     0

# ifconfig
em0: flags=8843<UP,BROADCAST,RUNNING,SIMPLEX,MULTICAST> metric 0 mtu 1500
        options=1db<RXCSUM,TXCSUM,VLAN_MTU,VLAN_HWTAGGING,POLLING,VLAN_HWCSUM,TSO4>
        ether 00:15:17:1f:e2:18
        media: Ethernet 1000baseTX <full-duplex>
        status: active
vlan2: flags=8843<UP,BROADCAST,RUNNING,SIMPLEX,MULTICAST> metric 0 mtu 1500
        options=3<RXCSUM,TXCSUM>
        ether 00:15:17:1f:e2:18
        inet X.X.X.X netmask 0xfffffff8 broadcast X.X.X.X
        media: Ethernet 1000baseTX <full-duplex>
        status: active
        vlan: 1000 parent interface: em0

# ipf -T list
fr_flags        min 0   max 0xffffffff  current 0
fr_active       min 0   max 0   current 0
fr_control_forwarding   min 0   max 0x1 current 0
fr_update_ipid  min 0   max 0x1 current 0
fr_chksrc       min 0   max 0x1 current 0
fr_minttl       min 0   max 0x1 current 4
fr_icmpminfragmtu       min 0   max 0x1 current 68
fr_pass min 0   max 0xffffffff  current 134217730
fr_tcpidletimeout       min 0x1 max 0x7fffffff  current 3600
fr_tcpclosewait min 0x1 max 0x7fffffff  current 60
fr_tcplastack   min 0x1 max 0x7fffffff  current 60
fr_tcptimeout   min 0x1 max 0x7fffffff  current 300
fr_tcpclosed    min 0x1 max 0x7fffffff  current 60
fr_tcphalfclosed        min 0x1 max 0x7fffffff  current 120
fr_udptimeout   min 0x1 max 0x7fffffff  current 120
fr_udpacktimeout        min 0x1 max 0x7fffffff  current 24
fr_icmptimeout  min 0x1 max 0x7fffffff  current 120
fr_icmpacktimeout       min 0x1 max 0x7fffffff  current 12
fr_iptimeout    min 0x1 max 0x7fffffff  current 120
fr_statemax     min 0x1 max 0x7fffffff  current 4013
fr_statesize    min 0x1 max 0x7fffffff  current 5737
fr_state_lock   min 0   max 0x1 current 0
fr_state_maxbucket      min 0x1 max 0x7fffffff  current 26
fr_state_maxbucket_reset        min 0   max 0x1 current 1
ipstate_logging min 0   max 0x1 current 1
fr_nat_lock     min 0   max 0x1 current 0
ipf_nattable_sz min 0x1 max 0x7fffffff  current 16383
ipf_nattable_max        min 0x1 max 0x7fffffff  current 300000
ipf_natrules_sz min 0x1 max 0x7fffffff  current 2047
ipf_rdrrules_sz min 0x1 max 0x7fffffff  current 2047
ipf_hostmap_sz  min 0x1 max 0x7fffffff  current 8191
fr_nat_maxbucket        min 0x1 max 0x7fffffff  current 28
fr_nat_maxbucket_reset  min 0   max 0x1 current 1
nat_logging     min 0   max 0x1 current 1
fr_defnatage    min 0x1 max 0x7fffffff  current 1200
fr_defnatipage  min 0x1 max 0x7fffffff  current 120
fr_defnaticmpage        min 0x1 max 0x7fffffff  current 6
fr_nat_doflush  min 0   max 0x1 current 0
ipf_proxy_debug min 0   max 0xa current 0
ipfr_size       min 0x1 max 0x7fffffff  current 257
fr_ipfrttl      min 0x1 max 0x7fffffff  current 120
ipl_suppress    min 0   max 0x1 current 1
ipl_logmax      min 0   max 0x7fffffff  current 7
ipl_logall      min 0   max 0x1 current 0
ipl_logsize     min 0   max 0x80000     current 8192
ippr_ftp_debug  min 0   max 0xa current 0