Online F5CAB2 Questions Video

By default, when a pool member is marked "down" by a monitor, the BIG-IP system stops sendingnewconnections to that member, but it typically allows existing connections to time out naturally (or resets them depending on profile settings).

Action on Service Down:This setting is configured at thePoollevel.

Reselect:When set toReselect, if a pool member is marked down, the BIG-IP system will immediately attempt to pick a different available pool member for any existing, active connections associated with the failed member.

Client Experience:This is used to maintain the user session by transparently moving the traffic to a healthy server without the client needing to re-establish the connection to the Virtual Server.

In a BIG-IP environment, load balancing and persistence work together but serve different purposes. While a load balancing method likeLeast Connectionsattempts to distribute traffic based on current connection counts, apersistence profileoverrides this logic for returning clients.

Persistence Overrides Load Balancing:When a persistence profile (such as Source Address or Cookie persistence) is applied to a Virtual Server, the BIG-IP system tracks which client was sent to which backend member.

Sticky Sessions:If a client with a valid persistence record returns, the BIG-IP will send that client to thesame pool memberit was previously assigned to, regardless of the load balancing algorithm's current preference.

Uneven Distribution:If certain clients generate significantly more traffic or stay connected longer than others, the persistence table will "lock" those high-volume flows to specific members, resulting in an uneven distribution of connections across the pool.

In BIG-IP high availability (HA) configurations, MAC Masquerade is used to speed up failover by allowing traffic-group-associated Self IPs to retain the same MAC address when moving between devices. This prevents upstream switches and routers from having to relearn ARP entries during a failover event, resulting in near-instant traffic recovery.

By default, MAC masquerade applies one MAC address per traffic group, regardless of how many VLANs the traffic group spans. This can create problems in some network designs because the same MAC address appearing on multiple VLANs may violate network policies or confuse switching infrastructure.

To address this, BIG-IP provides Per-VLAN MAC Masquerade, enabled by the database variable:

`tm.macmasqaddr_per_vlan = true`

When this feature is enabled:

BIG-IP derives a unique MAC address per VLAN

The base MAC address configured on the traffic group remains the first four octets

The last two octets are replaced with the VLAN ID expressed in hexadecimal

The VLAN ID is encoded in network byte order (high byte first, low byte second)

### VLAN ID Conversion:

VLAN ID: 1501 (decimal)

Convert to hexadecimal:

1501₁₀ = 0x05DD

High byte: 05

Low byte: DD

### Resulting MAC Address:

Base MAC: `02:12:34:56:00:00`

Per-VLAN substitution → last two bytes = `05:DD`

Final MAC address:

`02:12:34:56:05:dd`

### Why the Other Options Are Incorrect:

A (01:15) – Incorrect hexadecimal conversion of 1501

B (dd:05) – Byte order reversed (little-endian, not used by BIG-IP)

D (15:01) – Uses decimal values instead of hexadecimal

### Key BIG-IP HA Concept Reinforced:

Per-VLAN MAC Masquerade ensures Layer 2 uniqueness per VLAN while preserving the fast failover benefits of traffic groups, making it the recommended best practice in multi-VLAN HA deployments.