What is optimal MTU for VPN?

Summary

Optimal MTU for VPN

When it comes to setting the optimal MTU (Maximum Transmission Unit) for VPN (Virtual Private Network) connections, there are a few factors to consider. We recommend a value of 1460 bytes, as this ensures that your peer VPN gateway and the Cloud VPN gateway match. However, please note that the actual MTU for packets using a VPN tunnel can be lower than the Cloud VPN payload MTU if there are any elements in the network path that have a lower MTU. It’s always important to test and adjust the MTU based on your specific network setup.

How to Set MTU for VPN

If you are wondering how to set the MTU for VPN, the process may vary depending on the VPN solution you are using. In general, the steps to set the MTU involve accessing the configuration settings of your VPN gateway or client software. Here is an example of how to set the MTU for a BOVPN (Branch Office VPN) virtual interface:

1. Select the VPN > BOVPN Virtual Interfaces option.
2. Choose the virtual interface you want to configure and click Edit.
3. Under VPN Routes, locate the option to Restrict Tunnel MTU.
4. In the corresponding text box, you can either keep the default value of 1400 or enter a value between 68 and 9000, depending on your requirements.

Key Points

1. Recommended MTU for WAN on PPPoE DSL Networks

It is generally recommended that the MTU for a WAN interface connected to a PPPoE DSL network be 1492. This value is discovered as the maximum allowed MTU through auto MTU discovery. However, some experts argue that an MTU of 1452 provides the most optimal performance.

2. MTU Size for L2TP VPN

When encapsulating a 1500-byte IP packet into L2TP (Layer 2 Tunneling Protocol), the resulting encapsulated packet becomes 1540 bytes. To transmit this packet over a standard Ethernet-type interface with an MTU of 1500 bytes, fragmentation is required.

3. MTU Size for IPsec

When using IPsec (Internet Protocol Security), it is customary to set the MTU size on tunnel interfaces to 1400 bytes and the TCP-MSS-adjust to 1360 bytes. These values can be configured on a Cisco IOS device.

Questions and Answers

1. What is the best MTU for VPN?

The best MTU for VPN is recommended to be 1460 bytes for matching the Cloud VPN gateway’s payload MTU with your peer VPN gateway.

2. How do I set the MTU for VPN?

The steps for setting the MTU for VPN depend on your specific VPN solution. In general, you need to access the configuration settings for your VPN gateway or client software and look for options to adjust the MTU.

3. Is an MTU of 1492 or 1480 preferable for WAN on PPPoE DSL networks?

It is generally recommended to set the MTU to 1492 for WAN interfaces connected to PPPoE DSL networks. This value is discovered as the maximum allowed MTU through auto MTU discovery. However, some experts argue that an MTU of 1452 provides the most optimal performance.

4. Should I set the MTU to 1500 or 1492?

The MTU for Ethernet connections is typically set to 1500 bytes, but for WAN interfaces connected to PPPoE DSL networks, it is generally recommended to set the MTU to 1492. However, some experts argue that an MTU of 1452 provides the most optimal performance.

5. What is the MTU size for IPsec?

When using IPsec, it is customary to set the MTU size on tunnel interfaces to 1400 bytes. Additionally, the TCP-MSS-adjust is often set to 1360 bytes to account for the overhead of IPsec.

6. Is an MTU of 1472 or 1500 recommended?

If you can successfully ping with a payload size of 1472 bytes, it indicates that the total MTU is 1500 (1472 bytes payload + 20 bytes IP header + 8 bytes ICMP header). If the ping fails due to the packet being too large, you may receive a “Packet needs to be fragmented but DF set” error message.

7. Is an MTU of 9000 or 9216 preferable?

For the MTU on network devices like interfaces or routers, it is recommended to set it to be equal to or larger than the MTU size of the endpoints. In most cases, an MTU of 9000 is sufficient, but setting it to 9216 allows for any potential padding added by operating systems or intermediary devices.

8. Is an MTU of 1452 or 1492 more optimal?

While the generally recommended MTU for WAN interfaces connected to PPPoE DSL networks is 1492, some experts argue that an MTU of 1452 provides the most optimal performance due to reduced overhead.

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What is the best MTU for VPN

We recommend a value of 1460 bytes so that your peer VPN gateway and the Cloud VPN gateway match. The actual MTU for packets using a VPN tunnel can be lower than the Cloud VPN payload MTU if, for any reason, an element in the path has a lower MTU.

How to set MTU for VPN

Configure an MTUSelect VPN > BOVPN Virtual Interfaces.Select a virtual interface and click Edit.Click VPN Routes.Select Restrict Tunnel MTU.In the adjacent text box, keep the default value of 1400 or type a value between 68 and 9000.

What should my MTU be set at

It is generally recommended that the MTU for a WAN interface connected to a PPPoE DSL network be 1492. In fact, with auto MTU discovery, 1492 is discovered to be the maximum allowed MTU. However, having an MTU of 1452 is most optimal.

Why set MTU to 1400

Recommended MTU for overlay networking

WireGuard sets the Don't Fragment (DF) bit on its packets, and so the MTU for WireGuard on AKS needs to be set to 60 bytes below (or 80 bytes for IPv6) the 1400 MTU of the underlying network to avoid dropped packets.

Is MTU 1492 or 1480

The MTU size includes the data payload, any transport headers (such as TCP, UDP, GRE, RTP, or ICMP), and the IP header. It is generally recommended that the MTU for a WAN interface connected to a PPPoE DSL network be 1492. In fact, with auto MTU discovery, 1492 is discovered to be the maximum allowed MTU.

Is 1480 MTU good

A standard MTU is always around ~1500 for Ethernet (unless Jumbo Frames is enabled). It is just the packet size. If you are having trouble with MTU is due to the network adapter or router configuration.

What is the MTU size for L2TP VPN

When you encapsulate a 1500 byte IP packet into L2TP, the encapsulated packet becomes 1540 bytes (1500 + 40 bytes of IP, UDP and L2TP headers). You must fragment the packet in order to transmit it over a standard Ethernet-type interface (which has an MTU of 1500 bytes).

What is the MTU size of IPsec

When IPsec is being used, it is customary to set the MTU size on the tunnel interfaces to 1,400 bytes and to set the TCP-MSS-adjust to 1,360 bytes. This can be configured in a Cisco IOS device using these commands.

Should MTU be 1500 or 1492

It is generally recommended that the MTU for a WAN interface connected to a PPPoE DSL network be 1492. In fact, with auto MTU discovery, 1492 is discovered to be the maximum allowed MTU. However, having an MTU of 1452 is most optimal.

Is MTU 1472 or 1500

If the ping is successful (no packet loss) at 1472 payload size, the MTU will be "1472 (payload size) + 20 (IP Header) + 8 (ICMP Header)" = 1500. If the packet was too large you will get the message: "Packet needs to be fragmented but DF set" (with 100% packet LOSS).

Should MTU be 9000 or 9216

The FI MTU should never be less than the MTU size of the endpoints. Just remember, the FI is a simple L2 device and doesn't do any fragementation. Therefore, it is okay to set the MTU on the FI to 9000 but no harm at setting it at 9216 in case of any padding added by OS, intermediary devices (vFW, vRouters, etc), etc.

Should MTU be 1452 or 1492

It is generally recommended that the MTU for a WAN interface connected to a PPPoE DSL network be 1492. In fact, with auto MTU discovery, 1492 is discovered to be the maximum allowed MTU. However, having an MTU of 1452 is most optimal.

Is MTU of 1452 most optimal

With the MTU on PPPoE connections set to 1452 the overhead per frame is reduced by 0.44%. This translates into a faster Internet connection. On a standard T1 at 1.544 Mbps, this means an increase of about 10 kbps.

Should I set MTU to 1500

Ethernet MTU

The standard size MTU for Ethernet is 1,500 bytes. This does not include the Ethernet header of 18 or 20 bytes, and is the theoretical maximum amount of data that can be transmitted by the physical link. The MTU of any higher-level protocols must fit within this MTU.

What is the default MTU size for ipsec

1500

Configures the MTU size for the interface VLAN. bytes—The range is 64 to 9216; the default is 1500.

What is the default MTU size for OpenVPN

1500

However, some networks (such as PPPoE) may need a lower value of MTU. The default MTU value of OpenVPN is 1500 and for WireGuard it is 1420. If you have issues with certain websites or your VPN connection occasionally drops, try changing the MTU value.

What is the most common MTU size

1500 bytes

The common value of MTU on the internet is 1500 bytes.

What is the MTU of a Cisco ASA VPN

By default, the maximum TCP MSS on the ASA is 1380 bytes. This default accommodates IPv4 IPsec VPN connections where the headers can equal up to 120 bytes; this value fits within the default MTU of 1500 bytes.

What happens if MTU size is too high

The MTU of the next receiving device is determined before sending a packet to it. If the packet is too large and the next receiving device cannot accept it, the packet is divided into multiple packets and sent. This is called fragmentation. Fragmentation is bad for performance, as it adds delay and extra data.

Why set MTU to 9000

For Ethernet networks, the recommended MTU size is usually 9000 bytes. This is because Ethernet networks are designed to handle larger frames, making it easier to achieve higher performance with JUMBO Frames.

What happens if MTU is set too high

The MTU of the next receiving device is determined before sending a packet to it. If the packet is too large and the next receiving device cannot accept it, the packet is divided into multiple packets and sent. This is called fragmentation. Fragmentation is bad for performance, as it adds delay and extra data.

Is MTU 1500 or 1518

The size of 1500 bytes is the default Ethernet MTU value. Network layer protocols, such as the IP protocol, determine whether to fragment the data sent from the upper layer based on the MTU.

What is the MTU of a Cisco VPN

1500 byte

Since VPN encapsulation adds additional overhead to packets, reducing Maximum Transfer Units below the standard 1500 byte ethernet frame MTU helps to ensure that encapsulated packets are not fragmented. To check for packet fragmentation, ping with the "do not fragment" switch can be used.

What is the MTU problem in IPSec tunnel

The issue occurs when the server or the client send relatively big packets as they are not aware of the MTU on the path. MTU on the path may be lower (due to the tunnel overhead), than what is configured on their local interfaces (usually client and server will have Ethernet interface with MTU of 1500 bytes).

What is the default MTU size for IPsec

1500

Configures the MTU size for the interface VLAN. bytes—The range is 64 to 9216; the default is 1500.