Create and verify a jumbo frame MTU network
This page walks you through creating a Virtual Private Cloud (VPC) network and a pair of VMs for testing. It assumes you are generally familiar with network MTU .
Create an auto mode VPC network
Console
-
In the Google Cloud console, go to the VPC networkspage.
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Select a project in the project pull-down menu.
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Click Create VPC network.
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Enter a Namefor the network.
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Choose Automaticfor the Subnet creation mode.
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Set the Maximum transmission unit (MTU)field to
8896
. -
Click Create.
Create firewall rules
Console
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In the Google Cloud console, go to the Firewall policiespage.
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Click Create firewall rule.
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Enter a Namefor the firewall rule.
This name must be unique for the project. -
In the Networkpull-down menu, specify the name of the network you created.
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In the Targetspull-down menu, select All instances in the network.
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From the Source filterpull-down menu, select IPv4 ranges.
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In the field enter 10.128.0.0/16.
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In Protocols and ports, select Specified protocols and ports.
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Check the tcpcheckbox and enter 22in the field.
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Check the Other protocolscheckbox and enter icmpin the field.
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Click Create.
Create VMs
This section shows you how to create two VM instances for testing.
Console
Do these steps twice to get two VMs in the same zone.
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In the Google Cloud console, go to the VM instancespage.
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Click Create instance.
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Specify a Namefor your first VM.
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Click Networking, Disks, Security, Management, Sole-tenancy.
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Click Networking.
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In Network interfaces, click default default (10.128.0.0/20).
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In the Networkpull-down menu, select the network you created.
Connect to VM instances using SSH
Console
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In the Google Cloud console, go to the VM instancespage.
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In the Connectcolumn of your first instance, click SSH.
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In the Connectcolumn of your second instance, click SSH.
Verify MTU
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In the terminal for your first VM, run the following command:
/sbin/ifconfig | grep mtu
The reported MTU should be
8896
.ens4: flags=4163
mtu 8896 lo: flags=73 mtu 65536 -
In the terminal for your second VM, install
tcpdump
:sudo apt-get install tcpdump --yes
-
In the terminal of your second VM, start
tcpdump
. Replace FIRST_VM_NAME with the name of your first VM.sudo tcpdump host FIRST_VM_NAME -v
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In the terminal of your first VM, ping your second VM. The ping command must specify a packet size that is 28 bytes smaller than the network MTU. Replace SECOND_VM_NAME with the name of your second VM.
ping SECOND_VM_NAME -c 10 -M do -s 8868
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Check your second VM. You should see something like the following:
tcpdump: listening on ens4, link-type EN10MB (Ethernet), snapshot length 262144 bytes 19:43:57.116005 IP (tos 0x0, ttl 64, id 0, offset 0, flags [DF], proto ICMP (1), length 8896) FIRST_VM_NAME .c. PROJECT_ID .internal > SECOND_VM_NAME .c. PROJECT_ID .internal: ICMP echo request, id 5253, seq 1, length 8876 19:43:57.116053 IP (tos 0x0, ttl 64, id 23961, offset 0, flags [none], proto ICMP (1), length 8896) SECOND_VM_NAME .c. PROJECT_ID .internal > FIRST_VM_NAME .c. PROJECT_ID .internal: ICMP echo reply, id 5253, seq 1, length 8876
The variables mean the following:
-
FIRST_VM_NAME
is a name of your first VM. -
SECOND_VM_NAME
is a name of your second VM. -
PROJECT_ID
is the ID of the project containing the VMs.
-
-
On your second VM, press
Ctrl-c
to stoptcpdump
. -
When you're done testing, delete your resources in the following order:
- Firewall rule and VM instances
- VPC network
What's next
- Learn more about MTU .
- Create a VPC network with a specified MTU .