Same Series Comparison: N9K-C9508 vs N9K-C9504, the "Brothers" of 8-Slot vs 4-Slot

Aug 08 , 2025 5

1. Same Series Comparison: N9K-C9508 vs N9K-C9504, the "Brothers" of 8-Slot vs 4-Slot

In Cisco’s Nexus 9500 series, the N9K-C9508 (hereinafter "9508") and N9K-C9504 (hereinafter "9504") are like "half-siblings"—sharing the same underlying architecture but differing significantly in slot count, positioning, and enterprise network adaptability. This article breaks down their real-world differences across 15 dimensions.

2. Performance Metrics: Processing Speed, Memory, and Storage "Quantitative Changes"

Both are based on Cisco’s Cloud Scale ASIC (CSA), but the 9508 achieves "whole-machine performance leap" with more slots:

• Processing Speed:

• Per-slot bandwidth: Both 400Gbps (CSA ASIC feature), but 9508’s total switching capacity reaches 25.6Tbps (8 slots × 400Gbps × 80% utilization), while 9504 offers 12.8Tbps (4 slots × 400Gbps × 80%).

• Latency: In VXLAN transparent transmission scenarios, 9508 achieves 0.6μs forwarding latency, compared to 9504’s 0.7μs (shorter internal switching path due to fewer slots).

• Running Memory:

• Base memory: 32GB DDR4 (expandable to 256GB) for both, but 9508 supports more complex traffic classification (up to 2 million flow rules), requiring larger memory caching; 9504 caps at 1 million flow rules, suited for small-to-medium traffic.

• Storage Capacity:

• Onboard storage: 9508 has 16GB eMMC (expandable to 64GB), 9504 has 8GB eMMC (expandable to 32GB);

• Expansion: 9508 supports USB3.0 external drives (max 2TB) for long-term log storage; 9504 only supports USB2.0 (max 500GB), with high-speed expansion limited by power constraints.

3. Feature Sets: Nuanced Differences from "Usable" to "User-Friendly"

Both support ACI (Application Centric Infrastructure) and EVPN-VXLAN, but 9508’s "multi-slot" design makes it more flexible in complex scenarios:

• 9508:

• Supports "hybrid module deployment"—simultaneously installing line cards (e.g., 400G QSFP-DD), service cards (e.g., firewall/load balancer), and expansion cards (e.g., 100G optics);

• Natively supports "large-scale VXLAN" (up to 1 million endpoints per tenant), ideal for multi-tenant cloud platforms.

• 9504:

• Service cards only support basic functions (e.g., enhanced QoS, BFD acceleration), unable to deploy hardware-based firewalls;

• VXLAN tenant endpoint cap at 500,000, better suited for single-data-center enterprise environments.

4. Design & Appearance: Visual Impact of "Big Player" vs "Compact Warrior"

• 9508:

• Dimensions: 2RU × 88mm width × 680mm depth (100mm deeper than 9504), front panel with 48×10G SFP+ ports + 4×400G QSFP-DD uplinks;

• Redundancy: Standard dual redundant power supplies (1+1 backup) + dual fan modules (N+1 backup), hot-swappable, suitable for 24/7 high-load operation;

• Cooling: Bottom-to-top airflow, requiring 600mm-deep racks, with strict data center cooling demands.

• 9504:

• Dimensions: 1RU × 88mm width × 530mm depth (more compact), front panel with 48×10G SFP+ ports + 2×400G QSFP-DD uplinks;

• Redundancy: Optional single power supply (non-mandatory), fan modules only support N redundancy (no +1 backup);

• Cooling: Front-to-rear through-flow ventilation, fitting 500mm-deep racks, better for small-to-medium machine rooms.

5. User Experience: Real Pains of Operations Teams

• 9508:

• Strengths: Supports "virtualized clustering" (vPC+), logically merging multiple 9508s into one device to simplify cross-chassis link management;

• Pain points: Complex configuration (managing module statuses across 8 slots), requiring 3+ months of learning for new engineers; large log storage (50GB/day) risks eMMC overflow without regular cleanup.

• 9504:

• Strengths: Lightweight CLI (50% fewer non-essential commands pruned), simpler "show interface" output for troubleshooting;

• Pain points: Limited expansion (4 slots), may require full replacement when adding new modules; no virtualized clustering, relying on external devices (e.g., VRRP) for dual-machine redundancy.

6. Cost-Effectiveness: Long-Term Investment Math

• Initial Purchase: 9508 ~¥1.2M (8-slot base config), 9504 ~¥650k (4-slot base config), nearly double the price.

• Expansion Costs:

• 9508 supports 400G/800G optics (~¥30k/module), 9504 only 400G (~¥20k/module);

• However, 9508 reduces device count (e.g., 2 units vs 4 for 2000 servers), saving rack space and cabling costs by ~30%.

• Maintenance Costs:

• 9508 requires ACI premium licenses (~¥80k/year), supporting automated ops (Ansible integration);

• 9504 has no license fees but longer manual troubleshooting time (1.5+ extra hours daily).

7. Product Advantages: Scenario-Driven "Best Fit"

• 9508 Core Advantages: Ultra-high performance (25.6Tbps), flexible expansion (hybrid modules), high reliability (dual power/fans); ideal for hyperscale data centers, cloud provider cores, and multi-tenant platforms.

• 9504 Core Advantages: Compact size (1RU), low upfront cost, simplified ops; suited for enterprise campus cores, medium data centers, and branch aggregation.

8. System Upgrade: Details Determine Success (Key Section)

Upgrade Scenario: Migrating from NX-OS 9.2(5) to 10.5(2)F (supporting IPv6 SRv6 and hardware encryption).

Upgrade Process & Challenges:

1. Pre-Check Phase:

• Issue: 9508 may have "module firmware mismatches" (e.g., a service card stuck at 9.2(3)), causing failures; 9504 with non-Cisco optics (third-party 10G SFP+) may report driver errors.

• Fix: Use show module firmware to verify all module versions, forcing synchronization with the main system; check optics with show interface transceiver vendor, replacing non-Cisco modules.

2. Backup & Rollback:

• Issue: 9508’s 16GB onboard storage may overflow when backing up full configs (with logs); 9504 without pre-inserted USB drives may timeout during TFTP backups (10G port transfers 100GB in ~27 mins).

• Fix: 9508 uses "split backups" (config first, then logs to external servers); 9504 uses copy running-config scp://admin@192.168.1.100/ for encrypted SSH transfers, avoiding TFTP packet loss.

3. Downtime Control:

• Issue: 9508’s "rolling upgrade" (slot-by-slot) may cause traffic anomalies if non-critical services (e.g., test VLAN DHCP) remain active; 9504’s full reboot may disrupt core apps (e.g., ERP) for 5-10 minutes.

• Fix: 9508 disables non-essential services (e.g., conf t ; no ip dhcp pool test-vlan) pre-upgrade, restoring them post-upgrade; 9504 uses "NSF/SSO" for sub-30-second downtime via active-standby alternation.

4. Post-Upgrade Validation:

• Issue: 9508’s new version enforces "strict IPv6 checks" (dropping unrouted IPv6 traffic), breaking legacy IPv4-only devices; 9504’s hardware encryption (IPSec) remains inactive (requires manual license activation).

• Fix: Use show ipv6 route to verify default routes, adding temporary IPv6 routes (e.g., ipv6 route 0.0.0.0/0 2001:db8::1); 9504 loads encryption licenses with license boot module c9500-ipservices and confirms activation via show crypto ipservices.

9. Product Use Cases

• 9508 Typical Scenarios:

• Cloud data center core: Supporting 200k+ VMs via ACI for cross-AZ traffic isolation, hybrid modules (400G line cards + firewall service cards) meet security/compliance needs.

• Multi-tenant financial platforms: Handling 1M+ endpoints per tenant with VXLAN, hardware QoS ensures sub-10μs latency for high-frequency trading.

• 9504 Typical Scenarios:

• Enterprise campus core: Connecting 300+ access switches, QoS prioritizes video conferencing (DSCP AF41), 1RU saves rack space.

• Branch aggregation: Supporting MPLS VPN with 50ms BFD failover, ensuring ERP stability between branches and headquarters.

10. Detailed Pros & Cons

11. Conclusion: How to Choose?

• 9508: Opt for hyperscale cloud data centers, multi-tenant platforms, or future expansion plans (e.g., adding service cards).

• 9504: Choose for small-to-medium networks (<5,000 endpoints), cost-sensitive deployments, or space/power-constrained machine rooms.