Local Traffic Manager
Local Traffic Manager
This domain covers the LTM object model and the configuration decisions an administrator makes: nodes, pool members, virtual servers, profiles, monitors, SNAT pools, VLANs, self IPs, and route domains. Questions often ask which object owns a behavior or what happens when objects conflict.
Core rules
- A node is an IP address; a pool member is a node plus a service port. State is tracked at both levels: a node marked down takes all its members down.
- Virtual server types differ: Standard (full proxy, profiles), Performance L4 (fast, limited L7), Forwarding IP (packet forwarding), and Stateless (UDP). Choose the type before adding profiles.
- Profiles are inherited from parent profiles; child settings override parent settings. A profile can be attached directly to a virtual server or inherited from another profile.
- SNAT pools and automap are configured on the virtual server; a SNAT pool needs enough addresses for concurrent connections.
- Route domains isolate IP space. Addresses in a non-default route domain use the percent-id suffix, for example 10.1.1.1%2.
- Priority groups activate only when a member priority group is the highest available; they are not a load-balancing method by themselves.
Worked example
An administrator needs an HTTP virtual server that preserves client IP addresses for logging but still allows pool members on a different subnet to reply. The design uses a SNAT pool with two addresses, an HTTP profile, a TCP profile, a source-IP persistence profile, and a pool with an HTTP monitor. Because SNAT changes the source, the application sees the SNAT address; the administrator adds an X-Forwarded-For insert in the HTTP profile to preserve the original client address. Source-IP persistence keeps a client on the same member for the session.
Traps
- Marking a node down instead of a pool member and taking out unrelated services.
- Using Automap when pool members cannot route back to the automap address.
- Forgetting the route-domain suffix in monitors, pool members, or iRules.
- Attaching a client SSL profile to a Performance L4 virtual server.
- Creating a pool member on a port that no application listens on and assuming the node state covers it.