Juniper MX204 vs MX304: Which Router Fits the Network?

The Juniper MX204 vs MX304 comparison is one of the most common platform decisions facing network architects, service providers, and enterprise WAN engineers today. Both routers sit within the Juniper Networks MX Series—the company’s flagship line of carrier-grade routing platforms and part of the broader MX lineup, Juniper Networks’ family of routers designed for a range of network sizes and requirements—but they target fundamentally different performance tiers, deployment scales, and infrastructure budgets.

The MX204 delivers 400 Gbps of system throughput in a compact 1 RU fixed-configuration chassis. The MX304 delivers up to 4.8 Tbps in a 2 RU modular chassis with three MPC line card slots. That is a 12x throughput difference in a platform that occupies only one additional rack unit. Understanding where that performance gap matters—and where it does not—is the key to making the right purchasing decision.

Overview of Juniper MX204 and MX304 Routers

Juniper MX204

The Juniper MX204 is a fixed-configuration, 1 RU universal routing platform designed for space-constrained, high-performance edge deployments. It provides 400 Gbps of system throughput with a fixed port configuration of four 100GbE QSFP28 interfaces and eight 10GbE SFP+ interfaces. The MX204 runs Junos OS and supports the full depth of enterprise and service provider routing protocols, including BGP, MPLS, EVPN, Segment Routing, and IS-IS.

The MX204 was released in late 2017 and has been popular among small to mid-sized ISPs and carriers for its compact design and high throughput, meeting the needs of customers who require efficient, high-performance routing

Juniper MX304

The Juniper MX304 is a modular, 2 RU universal routing platform built on Juniper’s Trio 5 chipset architecture. It delivers up to 4.8 Tbps of system throughput across three MPC (Modular Port Concentrator) line card slots, supporting interface speeds from 10GbE through 400GbE via QSFP-DD. The MX304 also runs Junos OS and supports dual Routing Engines for hitless failover.

The MX304 sits in the high-performance mid-range of the MX Series—above the MX204 in throughput and modularity, but below the chassis-scale MX480 and MX960 in maximum slot density. It serves as the primary platform for service provider edge routing, data center interconnect, enterprise WAN aggregation, and 5G mobile backhaul at metropolitan and regional scale. The MX304 is designed to meet expanding bandwidth demands with extensive automation capabilities, making it suitable for customers such as service providers and large enterprises.

Specification	MX204	MX304
System Throughput	400 Gbps	Up to 4.8 Tbps (full duplex)
Forwarding Rate	~297 Mpps	Up to 2 Bpps
Form Factor	1 RU, fixed configuration	2 RU, modular (3 MPC slots)
ASIC Architecture	Juniper Trio (earlier generation)	Juniper Trio 5
Fixed Ports	4x 100GbE QSFP28 + 8x 10GbE SFP+	None (all ports via MPC line cards)
Maximum 400GbE Ports	Not supported (100GbE max)	Up to 24x 400GbE (via MPC11E)
Maximum 100GbE Ports	4 (fixed)	Up to 96
MPC Line Card Slots	None (fixed configuration)	3 slots
Routing Engine	Single RE (integrated)	Dual RE support (separate modules)
Power Supply	Dual AC/DC (redundant)	Dual AC/DC (redundant)
Typical Power Draw	~250–350W	~1,200–1,800W (line card dependent)
Operating System	Junos OS	Junos OS
Routing Table Scale	Full Internet table (1M+ IPv4)	Full Internet table (1M+ IPv4)
MACsec	Supported on 100GbE ports	Supported on MPC line cards at line rate
Timing/Sync	IEEE 1588v2, SyncE	IEEE 1588v2, SyncE
GRES / NSR	GRES supported; NSR limited by single RE	Full GRES and NSR with dual RE
Airflow	Side-to-back	Front-to-back
Weight	~14 lbs (6.4 kg)	~65 lbs (29.5 kg) fully loaded
Dimensions	1 RU (1.72″ H)	2 RU (3.5″ H)

The Juniper MX204 specs position it as a compact, cost-efficient edge router with fixed 100GbE connectivity and a system capacity ranging from 400 Gbps to 1.44 Tbps. The MX204 is a 1 RU fixed configuration router. In contrast, the Juniper MX304 specs place it in a different performance class entirely—modular, multi-terabit, 400GbE-capable, and built for deployments where throughput growth and interface flexibility are non-negotiable. The MX304 offers a higher system capacity of up to 4.8 Tbps, features a 2 RU modular platform, and supports dual routing engines for enhanced resiliency.

Key Architectural Differences Between MX204 and MX304

Processing Architecture

The MX204 and MX304 use different generations of Juniper’s purpose-built Trio ASIC architecture, and this difference is the primary driver of their performance gap.

MX204: Built on an earlier-generation Trio chipset optimized for compact, fixed-form-factor deployment. The ASIC handles all forwarding, QoS, and filter operations in hardware, but within the 400 Gbps throughput ceiling of the fixed chassis. There is no line card modularity—all forwarding capacity is integrated into the single-board architecture.

MX304: Built on the Trio 5 chipset—Juniper’s current-generation routing silicon. Trio 5 delivers significantly higher forwarding rates (up to 2 Bpps), deeper buffer capacity, and enhanced inline services processing. The modular MPC architecture means forwarding capacity scales with line card population, from a single MPC up to the full three-slot configuration.

The practical consequence: the MX204 is a fixed-performance platform. What you deploy is what you get—400 Gbps, 12 ports, no expansion path. The MX304 is a scalable platform. You can start with one MPC and add capacity over time, growing from a few hundred Gbps to the full 4.8 Tbps as traffic demands increase.

Port Density and Scalability

MX204 provides a fixed port layout: four 100GbE QSFP28 interfaces and eight 10GbE SFP+ interfaces. This is sufficient for peering with a small number of upstream providers, aggregating several 10GbE branch circuits, or serving as a compact DCI termination point. However, there is no path to adding more ports without deploying a second MX204. Generally, larger MX series routers like the MX240, MX480, and MX960 offer greater scalability compared to the fixed-capacity MX204.

MX304 provides modular port density via three MPC line card slots. Depending on the MPC model installed, the MX304 can deliver up to 24x 400GbE, up to 96x 100GbE, or mixed-speed configurations combining 400GbE, 100GbE, 40GbE, 25GbE, and 10GbE interfaces. This flexibility makes the MX304 adaptable to peering fabrics, DCI, WAN aggregation, and multi-service edge roles—often within the same chassis.

Pro Tip: If your deployment requires more than four 100GbE interfaces today—or is likely to within 18 months—the MX304 is the more cost-effective choice long-term. Deploying multiple MX204s to overcome port limitations adds management complexity and rack space without the architectural elegance of a single modular platform.

Redundancy and Reliability

This is one of the most significant architectural differences and often the deciding factor for production-critical deployments.

MX204: Operates with a single integrated Routing Engine. The chassis supports redundant power supplies and GRES (Graceful Routing Engine Switchover) at the Junos level, but there is no hardware RE redundancy. If the RE fails, the router goes down. For production peering or WAN headend roles, this means network-level redundancy (a second MX204 in a failover pair) is required to achieve high availability.

MX304: Supports dual Routing Engines as separate, hot-swappable modules. With dual REs, the MX304 provides Nonstop Active Routing (NSR), Nonstop Bridging (NSB), and hitless GRES. A control plane failure on the primary RE triggers an automatic, sub-second switchover to the backup RE with zero traffic impact. This is carrier-grade redundancy—and it is built into a single 2 RU chassis.

For any deployment where a single point of failure is unacceptable—production SP edge, WAN headend, DCI border—the MX304’s dual-RE capability is a material advantage over the MX204’s single-RE architecture.

Performance Comparison: Throughput, Latency, and Scalability

The performance gap between the MX204 and MX304 is substantial—and it manifests across throughput, forwarding rate, and scalability headroom. The MX304 offers up to 4.8 Tbps of throughput, while the MX204 supports a maximum of 1.44 Tbps. This difference in system capacity means that, although the MX304 comes at a higher price point, its cost-per-bit economics may be more favorable for users who require greater throughput and dense high-speed interfaces like 100 GbE and 400 GbE. Both platforms leverage advanced switching technology to deliver high throughput and low latency, ensuring efficient data traffic management for demanding network environments.

Throughput

The MX204 delivers 400 Gbps of system throughput—sufficient for deployments handling up to approximately 300–350 Gbps of production traffic (reserving headroom for traffic bursts and convergence events). The MX304 delivers up to 4.8 Tbps—a 12x increase that supports multi-terabit peering, DCI, and aggregation workloads.

For users who require greater system capacity, the MX304’s 4.8 Tbps throughput offers a significant cost-per-bit advantage, as its higher price is justified by the ability to support dense high-speed interfaces like 100 GbE and 400 GbE, compared to the MX204’s maximum of 1.44 Tbps.

To put this in perspective: a medium ISP with 200 Gbps of aggregate peering traffic fits comfortably on an MX204. A regional ISP with 1.5 Tbps of peering traffic requires an MX304. A Tier-2 provider with 3+ Tbps needs the MX304 or larger.

Forwarding Rate

The MX204 forwards at approximately 297 Mpps (million packets per second). The MX304 forwards at up to 2 Bpps (billion packets per second)—roughly a 7x improvement. Both platforms feature advanced switching capabilities, enabling them to handle high forwarding rates and support efficient data traffic management in demanding network environments. For deployments handling high packet rates (DDoS scrubbing, VoIP aggregation, IoT sensor traffic), forwarding rate can be the binding constraint rather than raw throughput.

Scalability Headroom

The MX204 has no expansion path. Its 400 Gbps capacity is fixed. The MX304 can be deployed initially with one or two MPC line cards and expanded to three as traffic grows. This pay-as-you-grow model is particularly valuable for organizations that expect significant traffic growth over a 3–5 year planning horizon but cannot justify the full capital investment on day one.

Performance Metric	MX204	MX304
System Throughput	400 Gbps	Up to 4.8 Tbps
Forwarding Rate	~297 Mpps	Up to 2 Bpps
Throughput per RU	400 Gbps/RU	2.4 Tbps/RU
Expansion Path	None (fixed)	Add MPC line cards (1–3 slots)
Max 400GbE Interfaces	None	Up to 24
Latency	Sub-microsecond (hardware forwarding)	Sub-microsecond (Trio 5 hardware forwarding)

Use Case Comparison: When to Choose MX204 vs MX304

Best Fit: MX204

For ISPs handling under 300 Gbps of aggregate peering traffic, the MX204 delivers carrier-grade routing in the most compact and cost-efficient form factor available in the MX Series. Its four 100GbE uplinks support peering with multiple transit providers or IXP connections, while the eight 10GbE ports handle customer aggregation. The MX204’s full Internet routing table support and BGP/MPLS capabilities meet the protocol requirements of small-to-medium ISP operations without the cost or complexity of a modular platform.

Large Enterprise WAN Edge

Best Fit: MX204 for moderate WAN; MX304 for high-throughput or growing WAN

Enterprise WAN headend requirements vary widely. An organization with 10–20 branch sites aggregating at under 50 Gbps of WAN traffic is well-served by the MX204. An enterprise with 50–200 branch sites, multiple MPLS or SD-WAN overlays, and 200+ Gbps of aggregate WAN traffic needs the MX304’s modular capacity and dual-RE redundancy. The decision threshold is typically around 100–200 Gbps of WAN aggregation traffic and the need for hardware-level RE failover.

Hyperscale Data Centers and Cloud Edge

Best Fit: MX304

Data center interconnect and cloud edge deployments demand 400GbE interfaces, multi-terabit throughput, and MACsec encryption at line rate. High-performance routing at the network edge is critical for supporting these scenarios, enabling secure and efficient connectivity between data centers and cloud environments. The MX204 does not support 400GbE and cannot deliver the throughput density these environments require. The MX304’s QSFP-DD support, EVPN-VXLAN capability, and 4.8 Tbps throughput make it the clear choice for DCI border routing, cloud on-ramp termination, and peering fabric edge.

5G Backhaul and Mobile Edge Networks

Best Fit: MX304

5G mobile backhaul requires low-latency forwarding, precise timing synchronization (IEEE 1588v2, SyncE), and high throughput to aggregate traffic from distributed radio access networks. While both the MX204 and MX304 support timing protocols, the MX304’s multi-terabit capacity and Trio 5 forwarding engine provide the scale needed for cell site aggregation at metropolitan and regional scope. Mobile operators deploying at scale almost universally require the MX304 or larger.

Remote and Edge Aggregation Sites

Best Fit: MX204

For remote PoPs, small colocation peering points, or edge aggregation sites where rack space is extremely limited and throughput requirements are under 400 Gbps, the MX204’s 1 RU footprint and low power draw (~250–350W) make it the practical choice. Its low power consumption is a key advantage for remote and edge aggregation sites, helping reduce operational costs and supporting energy-efficient network infrastructure. Deploying an MX304 in a remote site with only 50 Gbps of traffic is over-provisioning that wastes capital and power.

Cost Considerations: Juniper MX204 vs MX304

The MX204 and MX304 sit at different price points reflecting their performance tiers. While specific pricing varies by configuration, channel, and whether the unit is new or refurbished, the cost structure differs across several dimensions.

• Capital expenditure. The MX304 chassis, MPC line cards, and dual Routing Engines represent a significantly higher upfront investment than a single MX204. The MX304 is reported to be approximately three times the price of the MX204, making it a more expensive option for users. The MX204 was considered an affordable entry point to 100G networking, while the MX304, being a larger and more capable unit, comes with a significantly higher price tag. However, a single MX304 may replace multiple MX204s in high-throughput scenarios—making the per-Gbps cost potentially lower at scale.
• Licensing. Both platforms use the same Junos licensing model. Base routing features are included; advanced features (MACsec, specific MPLS services, Mist AI integration) may require additional licenses. The licensing cost difference between platforms is minimal for equivalent feature sets.

Refurbished market. Both the MX204 and MX304 are available as refurbished networking hardware at 50–65% below new-unit pricing. For organizations evaluating the Juniper MX204 vs MX304, refurbished procurement can make the MX304 accessible at or near the new-unit price of an MX204—effectively upgrading performance tier without increasing budget. Additionally, platforms like the MX204 and MX304 can sometimes be found on eBay as used or discounted equipment options, providing another avenue for cost savings.

Migration Considerations: Moving from MX204 to MX304

The MX304 is the natural upgrade path for organizations outgrowing MX204 deployments. As the MX204 is being replaced by the MX304, which offers significantly higher throughput and additional features but at a higher price point, organizations should take a forward-looking approach to network upgrades. Planning forward for future technology lifecycle management is essential, especially when considering lead times, end of support dates, and the availability of future replacement models. Migration scenarios typically arise when:

• Aggregate throughput exceeds 300–350 Gbps and approaching the MX204’s 400 Gbps ceiling
• The deployment needs more than four 100GbE interfaces or requires 400GbE uplinks
• Hardware-level RE redundancy becomes a requirement for production SLA compliance
• Traffic growth projections indicate the MX204 will be capacity-constrained within 12–18 months

Migration from MX204 to MX304 is operationally straightforward because both platforms run Junos OS. Configuration syntax, routing policy, and automation scripts transfer directly. The primary migration work involves physical installation (rack, power, cabling), configuration adaptation for the modular MPC architecture, and validation of optics and interface assignments.

Organizations that anticipate an MX204-to-MX304 migration within 2–3 years should evaluate whether deploying the MX304 from the start—particularly as refurbished hardware—is more cost-effective than a two-phase deployment.

Juniper MX204 vs MX304 Decision Framework

Use this structured checklist to determine which platform fits your deployment. Generally speaking, the MX204 is suitable for smaller deployments, while the MX304 is better suited for larger, high-growth environments.

Choose the MX204 if:

• Your aggregate throughput requirement is under 300 Gbps with modest growth projections
• You need a maximum of four 100GbE interfaces and eight 10GbE interfaces
• Rack space is extremely limited (1 RU requirement)
• Power budget is constrained (under 400W available per device)
• The deployment is for a remote PoP, edge aggregation site, or lab/staging environment
• Network-level redundancy (dual MX204s) is acceptable in lieu of hardware RE redundancy
• Budget is the primary constraint and a refurbished MX304 is not available within range

Choose the MX304 if:

• Your current or projected throughput exceeds 400 Gbps
• You require 400GbE interfaces (QSFP-DD)
• Hardware-level dual RE redundancy is required for production SLA compliance
• You need modular port density—more than 12 total interfaces, or mixed-speed configurations
• The deployment is a service provider edge, DCI border, WAN headend, or 5G aggregation role
• You need incremental scalability (pay-as-you-grow line card expansion)
• Traffic growth projections indicate the MX204 will be outgrown within 18–24 months

Final Thoughts: Which Router Should You Choose?

The Juniper MX204 vs MX304 decision is ultimately a question of scale, growth trajectory, and redundancy requirements.

The MX204 is the right choice when you need carrier-grade routing capability—full Internet table, BGP, MPLS, Segment Routing—in the smallest, most power-efficient form factor available in the MX Series. It excels at remote edge deployments, compact peering points, moderate-throughput WAN headends, and any scenario where 400 Gbps of throughput and 12 fixed ports are sufficient.

The MX304 is the right choice when your deployment demands multi-terabit throughput, 400GbE interface density, modular expansion, or hardware-level control plane redundancy. It is the better long-term investment for growing networks, high-availability production environments, and any deployment where the MX204’s fixed capacity would become a constraint within 2–3 years.

Both platforms run identical Junos OS, support the same automation tooling, and deliver the same protocol depth. The decision is about matching the performance envelope to the actual workload—not about one platform being inherently better than the other.

Edit: While both routers share core software features, the MX304 offers greater scalability and future-proofing due to its modular design and higher port density, which is important for rapidly expanding networks.

Evaluate Both Platforms with Network Republic

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• Vendor-neutral advisory: we help you right-size the platform to the workload