When examining layer 3 LACP hashing, we need to analyze how switches process packet headers to determine link selection. The critical components are:

struct lacp_hash_input {
    uint32_t src_ip;    // Last 5 bits used
    uint32_t dst_ip;    // Last 5 bits used
    uint16_t src_port;  // TCP/UDP ports included
    uint16_t dst_port;
};

The key distinction lies in whether the hashing algorithm uses:

• End-to-end destination IP (client's public IP)
• Next-hop IP (router's interface IP)

Modern enterprise switches (like Cisco Nexus or Arista) typically implement end-to-end IP hashing. This means traffic to different clients will hash across different links, even when passing through the same router.

To test your specific switch's behavior:

# Capture LACP hash decisions
tcpdump -i eth0 -nn -v 'ip and (host client_ip or host router_ip)'

Then analyze which IP appears in the hash calculation by observing traffic distribution patterns.

For HP ProCurve switches, the hash mode can sometimes be adjusted:

# On HP 2910al series
configure terminal
trunk 1/1,1/2 trk1 lacp
lacp-trunk load-balance ip-sa-da

When hardware limitations prevent optimal hashing:

1. Implement ECMP routing with multiple /30 subnets
2. Use policy-based routing to force specific paths
3. Consider VLAN-based load balancing

Be aware that more granular hashing (including ports) may cause:

• Higher CPU utilization on switches
• Potential reordering of TCP packets
• Reduced effective bandwidth for single-flow scenarios

Layer 3 LACP destination address hashing operates at a fundamental level by creating a deterministic mapping between network flows and physical links. The algorithm typically uses these components:

hash = (src_ip XOR dest_ip) MOD number_of_links

The key distinction lies in which destination IP gets hashed:

• Next-hop hashing: Uses the immediate next device's IP (router's IP in your topology)
• End-to-end hashing: Uses the ultimate client IP address

Most enterprise switches (including Cisco and HP ProCurve series) implement next-hop hashing for L3 LACP:

// Typical switch ASIC pseudocode
uint8_t calculate_lacp_hash(packet_t pkt) {
    return (pkt.ip_src.last_byte ^ pkt.ip_dst.last_byte) % link_count;
}

For your HP ProCurve 2510G-24, verify the exact hashing behavior with:

# CLI command to check LACP hashing
show lacp hash-algorithm

Your current xmit_hash_policy=1 setting is correct for L3+L4 hashing. Alternative policies include:

# Available xmit_hash_policy values:
# 0 - layer2 (default)
# 1 - layer3+4
# 2 - layer2+3
# 3 - encap2+3
# 4 - encap3+4

For single-server/multi-client scenarios, these statistics show typical distribution:

When evaluating 2910al vs 2510G-24, consider these hardware specs:

• 2910al uses full 32-bit IP XOR operation
• 2510G-24 may only use last octet
• Newer switches support dynamic load threshold adjustment

These diagnostic commands help verify actual traffic distribution:

# On HP ProCurve switches
show lacp counters
show interface ethernet X/Y throughput

# On Linux servers
cat /proc/net/bonding/bond0
ethtool -S eth0 | grep packets

If LACP limitations persist, consider:

1. ECMP routing with BGP
2. VLAN-based traffic separation
3. Application-level sharding