Forum Discussion
How does F5 LTM route traffic to a subnet it's not aware of
I have the below setup, A VIP is configured with IP 192.168.0.3 for telnet service with snat automap to loadbalance all connections to 192.168.1.2.
PC1 (10.0.0.2/24) <--> (10.0.0.1/24) RTR1 (192.168.0.1/24) <--> (192.168.0.2/24) F5 LTM(192.168.1.2/24) <---> (192.168.1.1/24)Server1
There is not default route configured on the LTM.
When i initiate a telnet to 192.168.0.3 from PC1 ( 10.0.0.2), it works and I just don't know how it does ? without proper routing configured on the F5 - Can someone help me to understand how F5 is returning traffic 10.0.0.2 ?
Thanks,
Viks
- What_Lies_Bene1
Cirrostratus
This is the Auto Last Hop feature at work. This is enabled by default; rather than consulting the routing table to find a path to route return traffic to, the system simply returns it to the MAC address it came from; in this case the MAC for 192.168.0.1. No routes required! - viks_96432
Nimbostratus
Ah... Thanks a lot . Can we disable this feature ? - What_Lies_Bene1
Cirrostratus
You can disable this feature but it's enabled by default as it can be quite useful and remember it only applies to traffic directed at a Virtual Server. Don't think it's a security risk because it's effectively routing when you don't want it to, it won't do this for other traffic. - viks_96432
Nimbostratus
thanks :) - What_Lies_Bene1
Cirrostratus
You're welcome.
Recent Discussions
Related Content
* Getting Started on DevCentral
* Community Guidelines
* Community Terms of Use / EULA
* Community Ranking Explained
* Community Resources
* Contact the DevCentral Team
* Update MFA on account.f5.com