Mar 27, 2026 - For details about updated CVE-2025-53521 (BIG-IP APM vulnerability), refer to K000156741.

Forum Discussion

Hendroes_217893's avatar
Hendroes_217893
Icon for Altostratus rankAltostratus
Feb 09, 2017

Asymmetric routing F5 (different Inbound and outbound traffic)

Hi,   I tried to make asymmetric routes in F5. Traffic will come from Router A from internet, and will send it back through Router B.   I have read about the auto last hop that make the r...
application delivery
LTM
Kai_Wilke's avatar
Kai_Wilke
Icon for MVP rankMVP
Feb 09, 2017

Hi Hendroes,

the 

auto-last-hop
feature is enabled by default and causes the F5 to use the 
SRC_MAC
of the received connection as the next-hop MAC address while sending data through this connection.

If you disable the 

auto-last-hop
feature either globaly or individually on certain configuration object, the F5 will fallback to its L3 routing table to locate the next-hop mac while sending outgoing data through this connection.

In addition to that you can write some iRule to specify the next hop programatically based on every criteria you can think of and even more (via 

[nexthop]
command). This is Policy-Based-Routing (PBR) on steriods! 😉

For further reading: https://support.f5.com/csp/article/K13876

Cheers, Kai