Great idea, Nathan. Looks like we lose the POST data between the last F5 virtual server and the pool member.
The traffic goes to vs_parent_somesite_443 (where the rule above lives) -> vs_child_somesite -> pool member
....../Common/vs_parent_somesite_443
18:41:00.710491 IP 1.2.3.4.47813 > 3.4.5.6.http: P 0:945(945) ack 1 win 4380 in slot1/tmm1 lis=/Common/vs_child_somesite
....E...Z.@...b.
.=...j...P...5Yi`U...........
$..&$..&POST /signin HTTP/1.1
Host: somesite.myawesomedomain.com
Connection: keep-alive
Cache-Control: max-age=0
Accept: text/html,application/xhtml+xml,application/xml;q=0.9,image/webp,*/*;q=0.8
Origin: https://somesite.myawesomedomain.com
User-Agent: Mozilla/5.0 (Macintosh; Intel Mac OS X 10_10_1) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/38.0.2125.122 Safari/537.36
Content-Type: application/x-www-form-urlencoded
Referer: https://somesite.myawesomedomain.com/signin
Accept-Language: en-US,en;q=0.8
Cookie: _session=s1092tyahglskghado1i2
X-Forwarded-For: 1.2.3.4
b2
utf8=%E2%9C%93&authenticity_token=kflcZfoGoig%2ByR6U0x3Rw%2BO6qbjpRlUVGIBK0gZmWWQ%3D&user%5Bemail%5D=steve&user%5Bpassword%5D=mycoolpass&user%5Bremember_me%5D=0&commit=Go
......./Common/vs_child_somesite
18:41:00.710914 IP myexternalip.somesite.com.47813 > a-pool-member-ip.http: P 2845897884:2845898674(790) ack 1803219730 win 4380 out slot1/tmm1 lis=/Common/vs_child_somesite
....E..JZ.@....y
...
......P....kz......0......
$..&..q.POST /signin HTTP/1.1
Host: somesite.myawesomedomain.com
Connection: keep-alive
Cache-Control: max-age=0
Accept: text/html,application/xhtml+xml,application/xml;q=0.9,image/webp,*/*;q=0.8
Origin: https://somesite.myawesomedomain.com
User-Agent: Mozilla/5.0 (Macintosh; Intel Mac OS X 10_10_1) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/38.0.2125.122 Safari/537.36
Content-Type: application/x-www-form-urlencoded
Referer: https://somesite.myawesomedomain.com/signin
Accept-Language: en-US,en;q=0.8
Cookie: _session=s1092tyahglskghado1i2
X-Forwarded-For: 1.2.3.4
X-Forwarded-For: 1.2.3.4
......./Common/vs_child_somesite