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.
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)- A17% (7)
- B73% (30)
- C7% (3)
- D2% (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.
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.
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.
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.
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
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