Delayed connection when traffic crosses router domains in F5 BIG-IP

If you have isolated the route domains then traffic will have to exit F5 and then return again from the network, so latency could happen in that case and it is the design not F5 that is the issue in that case 😉

You can also do tcdumps in the 2 route domains and compare the timestamps:

https://my.f5.com/manage/s/article/K6546

https://techdocs.f5.com/en-us/bigip-14-1-0/big-ip-tmos-routing-administration-14-1-0/route-domains/traffic-forwarding-across-route-domains/about-strict-isolation.html