MTU Path Discovery & Fragmentation Analyzer
📦 MTU Path Discovery & Fragmentation Analyzer
Calculate effective MTU after encapsulation overhead, visualize fragmentation, and troubleshoot PMTUD issues
🏗️ Encapsulation Stack (Drag to reorder)
No encapsulation layers added. Add a layer below to see how it affects MTU.
Effective Payload MTU
1500
bytes available for data
Not saved
📖 How to Use This Tool
- Quick Start: Click a preset button (Internet, PPPoE, Azure, etc.) to load common scenarios
- Custom Calculation: Set your Base MTU and add encapsulation layers one at a time
- Results: See your effective payload MTU, recommended TCP MSS, and overhead breakdown
- Fragmentation: If MTU < 1500, a visual fragmentation diagram appears automatically
- Troubleshooting: Use the PMTUD flowchart to diagnose Path MTU Discovery issues
- Performance Impact: The bandwidth waste calculator shows the real cost of fragmentation
MTU Calculation Results
Effective Payload MTU
1500
bytes available for data
Total Overhead
0
bytes consumed
Recommended TCP MSS
1460
MTU - 40 (IP+TCP headers)
Base MTU:
1500 bytes
Encapsulation Overhead:
0 bytes
Effective MTU:
1500 bytes
IP + TCP Headers:
40 bytes (20 IP + 20 TCP)
Maximum TCP Payload:
1460 bytes
Efficiency:
97.3%
💸 Bandwidth Waste Calculator
ℹ️ Performance Impact: Calculate the real cost of fragmentation on your network bandwidth.
⚠ Wasted Bandwidth (Warning)
0
Mbps lost to fragmentation overhead
✗ Overhead Percentage (Critical)
0%
of total bandwidth wasted
⚠ Extra Fragments (Warning)
0
additional packets per second
Fragments per Original Packet:
1
Overhead per Packet:
0 bytes
Total Overhead per Second:
0 bytes
Recommended Action:
Increase MTU or enable PMTUD
🔍 Path MTU Discovery (PMTUD) Interactive Troubleshooter
ℹ️ Interactive Flowchart: Click through the diagnostic steps below to troubleshoot PMTUD issues.
🚀 Start: Having packet loss or slow performance?
Click to begin the diagnostic process. We'll walk through systematic troubleshooting steps.
🔧 Configuration Examples
ℹ️ TCP MSS Clamping: Configure these on your routers to prevent fragmentation.
! Cisco IOS/IOS-XE
interface GigabitEthernet0/0
ip tcp adjust-mss 1460
! Juniper JunOS
set interfaces ge-0/0/0 unit 0 family inet mtu 1500
set interfaces ge-0/0/0 unit 0 family inet tcp-mss 1460
# Linux iptables
iptables -t mangle -A FORWARD -p tcp --tcp-flags SYN,RST SYN -j TCPMSS --set-mss 1460
🚀 Jumbo Frame Analysis
ℹ️ Jumbo Frames: Larger MTU sizes improve throughput for storage and datacenter networks.
Standard Frame Efficiency:
97.3% (1460/1500)
Jumbo Frame (9000 MTU):
99.6% efficiency (8960/9000)
Frames per GB (Current):
~731,000 frames
Frames per GB (Jumbo 9000):
~119,000 frames (84% reduction)
CPU Savings (Jumbo vs Std):
~84% fewer interrupts
Recommendations:
- Standard 1500 MTU: Internet, general campus networks, mixed environments
- Baby Jumbos (2000): Metro Ethernet, some MPLS networks
- Jumbo Frames (9000): iSCSI, NFS, server-to-server, datacenter fabrics
- Super Jumbos (9216): Storage networks, 10GbE+ datacenter