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201 · Question #218

An LTM device has a virtual server mapped to www5f.com with a pool assigned. The objects are defined as follows: Virtual server: Destination 192.168.245.100.443 netmask 255.255.255.0 Persistence: Sour

The correct answer is B. netmask 255.255.255.255. To ensure each unique source IP address creates a distinct persistence record, the persistence profile's netmask must be set to 255.255.255.255, matching the entire IPv4 address.

Section 2: Configure Load Balancing Features

Question

An LTM device has a virtual server mapped to www5f.com with a pool assigned. The objects are defined as follows:

Virtual server: Destination 192.168.245.100.443 netmask 255.255.255.0 Persistence: Source address persistence netmask 255.0.0.0 SNAT: AutoMap Profiles: HnP/TCP How should the BIG-IP Administrator modify the persistence profile so that each unique IP address creates a persistence record?

Options

  • Anetmask 0.0.0.0
  • Bnetmask 255.255.255.255
  • Cnetmask 255.255.0.0
  • Dnetmask 255.256.255.0

How the community answered

(41 responses)
  • A
    17% (7)
  • B
    73% (30)
  • C
    7% (3)
  • D
    2% (1)

Why each option

To ensure each unique source IP address creates a distinct persistence record, the persistence profile's netmask must be set to 255.255.255.255, matching the entire IPv4 address.

Anetmask 0.0.0.0

A netmask of 0.0.0.0 would cause the persistence profile to consider only a portion (0 bits) of the source IP address, potentially treating all clients as the same for persistence purposes, which is incorrect.

Bnetmask 255.255.255.255Correct

Setting the netmask to 255.255.255.255 in a source address persistence profile ensures that the entire 32-bit IPv4 address is considered when creating persistence records. This means every individual, unique source IP address will establish its own persistence entry, effectively mapping one-to-one between a client IP and a backend server.

Cnetmask 255.255.0.0

A netmask of 255.255.0.0 would only consider the first two octets of the source IP address for persistence, meaning all clients within a /16 subnet would share the same persistence record.

Dnetmask 255.256.255.0

A netmask of 255.256.255.0 is an invalid netmask as '256' is not a valid octet value for an IPv4 netmask.

Concept tested: BIG-IP LTM source address persistence netmask

Source: https://techdocs.f5.com/en-us/bigip-15-1-0/big-ip-local-traffic-management-persistence-profiles-reference/source-address-persistence.html

Topics

#source address persistence#persistence profile#netmask#load balancing

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