specific source port translation

was syn-ack coming to correct vlan?

what version are you running? if it is 10.2.3+, you may try to log tcp rst packet.

sol13223:Configuring the BIG-IP system to log TCP RST packets

http://support.f5.com/kb/en-us/solutions/public/13000/200/sol13223.html

this is mine.

[root@ve10:Active] config  b virtual bar list
virtual bar {
   pool gw
   destination any:any
   mask 0.0.0.0
   ip protocol 6
   rules myrule
}
[root@ve10:Active] config  b pool gw list
pool gw {
   members 172.28.19.254:any {}
}
[root@ve10:Active] config  b rule myrule list
rule myrule {
   when CLIENT_ACCEPTED {
        snat 172.28.19.252 1234
}
}
[root@ve10:Active] config  b snat translation list
snat translation 172.28.19.252 {}

 tcpdump

[root@ve10:Active] config  tcpdump -nni 0.0 -s0 port 80
tcpdump: verbose output suppressed, use -v or -vv for full protocol decode
listening on 0.0, link-type EN10MB (Ethernet), capture size 65535 bytes
09:20:11.103550 IP 200.200.200.101.60204 > 172.28.19.251.80: S 4212438457:4212438457(0) win 5840  in slot1/tmm0 lis=
09:20:11.103603 IP 172.28.19.251.80 > 200.200.200.101.60204: S 2784638521:2784638521(0) ack 4212438458 win 4380  out slot1/tmm0 lis=bar
09:20:11.104573 IP 200.200.200.101.60204 > 172.28.19.251.80: . ack 1 win 46  in slot1/tmm0 lis=bar
09:20:11.104634 IP 172.28.19.252.1234 > 172.28.19.251.80: S 3603285261:3603285261(0) win 4380  out slot1/tmm0 lis=bar
09:20:11.105731 IP 200.200.200.101.60204 > 172.28.19.251.80: P 1:3(2) ack 1 win 46  in slot1/tmm0 lis=bar
09:20:11.105742 IP 172.28.19.251.80 > 172.28.19.252.1234: S 863226244:863226244(0) ack 3603285262 win 5792  in slot1/tmm0 lis=bar
09:20:11.105750 IP 172.28.19.252.1234 > 172.28.19.251.80: . ack 1 win 4380  out slot1/tmm0 lis=bar
09:20:11.105762 IP 172.28.19.252.1234 > 172.28.19.251.80: P 1:3(2) ack 1 win 4380  out slot1/tmm0 lis=bar
09:20:11.106790 IP 172.28.19.251.80 > 172.28.19.252.1234: . ack 3 win 46  in slot1/tmm0 lis=bar
09:20:11.205525 IP 172.28.19.251.80 > 200.200.200.101.60204: . ack 3 win 4382  out slot1/tmm0 lis=bar

 connection table

[root@ve10:Active] config  b conn client 200.200.200.101 show all
VIRTUAL any <-> NODE 172.28.19.251:80   TYPE any   1/0
    CLIENTSIDE 200.200.200.101:60204 <-> 172.28.19.251:80
        (pkts,bits) in = (3, 166)   out = (2, 116)
    SERVERSIDE 172.28.19.252:1234 <-> 172.28.19.251:80
        (pkts,bits) in = (2, 112)   out = (3, 170)
    PROTOCOL 6   UNIT 1   IDLE 4 (300)   LASTHOP internal 00:50:56:b3:01:0b