When the level of an IS-IS interface is changed, the adjacency must be re-established because IS-IS adjacencies are formed based on matching levels (Level-1, Level-2, or both). Other changes, such as cost or hello intervals, do not disrupt the existing adjacency but might impact routing metrics or timing .

Comprehensive and Detailed Step-by-Step Explanation:
Multi-Channel Protocols:
Multi-channel protocols use separate channels for control and data communication, requiring application- specific packet filtering (ASPF) to track sessions.
Examples:
FTP (A):Uses separate control and data channels.
SIP (B):Uses multiple ports for signaling and media.
H.323 (D):A VoIP protocol using multiple channels.
Single-Channel Protocol:
SMTP (C):A single-channel protocol for email communication, which does not require ASPF.
References:
HCIA-Datacom Study Guide, Chapter: Firewall ASPF Configuration
Huawei Multi-Channel Protocol Handling

Explanation of VLAN Pool Assignment Algorithms:
In WLANs,VLAN poolshelp reduce broadcast domains and improve network performance by distributing users across multiple VLANs. Two algorithms are used for VLAN assignment:
Even Assignment Algorithm:
The number of users in each VLAN is even.
This algorithm assigns users evenly across VLANs, ensuring a balanced distribution of users in each VLAN.
When STAs go offline and online again, their VLANs and IP addresses may easily change.
Since the assignment is based on maintaining even distribution, a device (STA) may not be assigned the same VLAN when it reconnects, leading to potential IP address changes.
Hash Assignment Algorithm:
The number of users in each VLAN is uneven.
The hash algorithm assigns users to VLANs based on a hash value (e.g., derived from the MAC address). This may result in an uneven distribution of users across VLANs.
VLANs and IP addresses remain unchanged for STAs that go offline and online again.
The hash algorithm ensures that a device reconnects to the same VLAN, preserving its IP address.
A screenshot of a computer Description automatically generated

VRRP and BFD Association:
VRRP (Virtual Router Redundancy Protocol) is used to provide gateway redundancy by electing amasterandbackuprouter.
Associating VRRP with BFD (Bidirectional Forwarding Detection) allows faster detection of faults on the master device or the link between the master and the backup.
HCIP-Datacom-Core Technology Training Material (VRRP and BFD Association).
Master_Down_Timer Behavior:
Normally, when a VRRP backup device detects that the master is down (through missed VRRP advertisements), theMaster_Down_Timerdictates the failover timing.
However, when VRRP is associated with BFD:
BFD detects faults immediately (sub-second detection).
The backup device doesnot wait for the Master_Down_Timerto expire. Instead, it immediately assumes the master role upon fault detection by BFD.
Reference:HCIP-Datacom-Core Technology Training Material (VRRP Failover Mechanism).
Why the Statement is FALSE:
The statement claims that the backup device assumes the master roleafter the Master_Down_Timer expireswhen a fault is detected by BFD.
This is incorrect because BFD bypasses the need for the Master_Down_Timer to expire. The backup device transitions to the master role immediately upon BFD detecting a fault.
Conclusion:
The correct behavior of VRRP when associated with BFD isimmediate role assumption by the backup deviceupon fault detection, bypassing the Master_Down_Timer.
Therefore, the statement isFALSE.

When configuring VRRP, the virtual router priority and virtual IP address are mandatory because they define the VRRP instance and its role within the group. Preemption mode and preemption delay are optional configurations that influence how routers take over the master role when priorities change. These are not mandatory for the VRRP protocol to function .