When dealing with HP ProCurve 2920 switches in a 2-node deployment for VoIP environments, the stacking architecture becomes critical. The stacking modules (J9730A for 2920 series) create a 20Gbps backplane connection between switches, which is significantly faster than standard trunked ports.

While the stacking solution adds approximately $1,800 to the project cost (modules + cables), consider these technical advantages:

• Single management interface (one IP address for both switches)
• Unified configuration and firmware management
• Automatic failover capabilities
• True stack synchronization (MAC tables, ARP, etc.)

For your specific 2-switch scenario, these are the practical configurations:

Option 1: Ring Topology (Recommended)

Switch1 StackPort1 <---> Switch2 StackPort2
Switch1 StackPort2 <---> Switch2 StackPort1

This provides full redundancy. If one stacking cable fails, communication continues through the alternate path.

Option 2: Chain Topology

Switch1 StackPort1 <---> Switch2 StackPort1

Simpler cabling but creates a single point of failure. Not recommended for production environments.

Option 3: Traditional Trunking

Switch1 Gig1/1 <---> Switch2 Gig1/1
Switch1 Gig1/2 <---> Switch2 Gig1/2

Configure as LACP trunk (example config):

interface GigabitEthernet 1/1
   channel-group 1 mode active
!
interface GigabitEthernet 1/2
   channel-group 1 mode active
!
interface Port-channel 1
   switchport trunk allowed vlan 1,100,200
   switchport mode trunk

With your traffic profile (100Mbps PC+phone combos), even a 2Gbps trunk would be sufficient bandwidth-wise. However, stacking provides:

• Lower latency between switches (backplane vs. network hops)
• Better QoS handling for voice traffic
• Simpler troubleshooting (single logical device)

For this VoIP deployment with no planned expansion, I recommend:

1. Invest in the stacking modules if budget allows - the operational benefits outweigh the cost
2. Implement a full ring topology using both stacking ports
3. If budget is constrained, implement a 4-port LACP trunk (requires 4 free ports)

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When deploying two HP ProCurve 2920-48G PoE switches in a VoIP environment, the fundamental question revolves around whether to invest in dedicated stacking modules or utilize standard trunking between switch ports. Let's break down the technical considerations:

// Pseudo-code for topology decision logic
if (budget_available && management_simplicity_needed) {
    implement_stacking();
} else if (redundancy_critical && bandwidth_requirements_high) {
    implement_dual_trunk();
} else {
    implement_single_trunk();
}

The stacking modules (J9732A) provide 20Gbps full-duplex bandwidth between switches through the dedicated stacking ports. For a two-switch deployment:

• Single-cable chain topology creates 20Gbps throughput but no redundancy
• Dual-cable ring topology provides 40Gbps aggregate bandwidth with failover capability

# Stacking configuration example
configure terminal
stacking
member 1 type J9729A
member 2 type J9729A
ports 1/1,2/1 enable
exit

Using regular Gigabit ports for trunking offers a cost-effective solution. A 4-port LACP trunk provides:

• 4Gbps full-duplex bandwidth (sufficient for 100Mbps phone+PC combos)
• Built-in redundancy through LACP failover
• No additional hardware costs

// Trunk configuration example (HP ProCurve CLI)
configure terminal
trunk A1-A4 trk1 lacp
vlan 1
untagged trk1
exit

Metric	Stacking (Dual-cable)	4-port LACP Trunk
Bandwidth	40Gbps	4Gbps
Failover Time	<1s	1-3s
Cost	$1800+	$0

For a call center with 48 phones per switch (96 total), let's examine traffic patterns:

• G.711 codec uses ~100kbps per call
• Simultaneous calls during peak: 30 per switch
• Total voice bandwidth: 3Mbps per switch
• PC traffic (behind phones): ~1Mbps average

Even during peak usage, a 4-port trunk provides sufficient headroom (4Gbps vs. ~8Mbps actual load).

If opting for trunking instead of stacking:

1. Use non-adjacent ports to minimize ASIC load
2. Enable spanning-tree portfast on phone ports
3. Configure QoS to prioritize voice traffic

# QoS configuration example
configure terminal
vlan 1
voice
exit
qos
priority high 10
exit

For this specific dual-switch VoIP deployment with limited port utilization and no growth plans, standard trunking between switches provides the most cost-effective solution while meeting all performance requirements. The $1800+ savings from skipping stacking modules could be better invested in UPS backup or network monitoring tools.