inbound snat question (ltm v11.4.0)

Client 172.21.123.4 (front side address 129.74.249.147) Virtual Server 129.74.5.169 Physical Server 172.19.232.215

tcpdump -nni 0.0:nnnp -s0 host 172.21.123.4 -v

tcpdump: listening on 0.0:nnnp, link-type EN10MB (Ethernet), capture size 65535 bytes 15:14:48.299221 IP (tos 0x0, ttl 254, id 15554, offset 0, flags [none], proto: UDP (17), length: 94) 129.74.249.147.51583 > 129.74.5.169.1812: RADIUS, length: 66 Access Request (1), id: 0x73, Authenticator: 129dc5c74c9b2022c7f8ca1f1f17880c Username Attribute (1), length: 10, Value: dbarstis Password Attribute (2), length: 18, Value: NAS IP Address Attribute (4), length: 6, Value: 129.74.249.147 NAS Port Attribute (5), length: 6, Value: 138 NAS Port Type Attribute (61), length: 6, Value: Virtual in slot1/tmm1 lis=/Common/forward_0 flowtype=65 flowid=5700829C2300 peerid=570081C69800 conflags=4000EE4 inslot=3 inport=32 haunit=0 peerremote=00000000:00000000:0000FFFF:814A05A9 peerlocal=00000000:00000000:0000FFFF:814AF993 remoteport=1812 localport=51583 proto=17 vlan=983 15:14:48.299234 IP (tos 0x0, ttl 253, id 15554, offset 0, flags [none], proto: UDP (17), length: 94) 129.74.249.147.51583 > 129.74.5.169.1812: RADIUS, length: 66 Access Request (1), id: 0x73, Authenticator: 129dc5c74c9b2022c7f8ca1f1f17880c Username Attribute (1), length: 10, Value: dbarstis Password Attribute (2), length: 18, Value: NAS IP Address Attribute (4), length: 6, Value: 129.74.249.147 NAS Port Attribute (5), length: 6, Value: 138 NAS Port Type Attribute (61), length: 6, Value: Virtual out slot1/tmm1 lis=/Common/forward_0 flowtype=129 flowid=570081C69800 peerid=5700829C2300 conflags=4000EE4 inslot=3 inport=32 haunit=1 peerremote=00000000:00000000:0000FFFF:814AF993 peerlocal=00000000:00000000:0000FFFF:814A05A9 remoteport=51583 localport=1812 proto=17 vlan=132