[[["易于理解","easyToUnderstand","thumb-up"],["解决了我的问题","solvedMyProblem","thumb-up"],["其他","otherUp","thumb-up"]],[["很难理解","hardToUnderstand","thumb-down"],["信息或示例代码不正确","incorrectInformationOrSampleCode","thumb-down"],["没有我需要的信息/示例","missingTheInformationSamplesINeed","thumb-down"],["翻译问题","translationIssue","thumb-down"],["其他","otherDown","thumb-down"]],["最后更新时间 (UTC)：2025-08-19。"],[],[],null,["# Create and verify a jumbo frame MTU network\n===========================================\n\nThis page walks you through creating a Virtual Private Cloud (VPC) network and\na pair of VMs for testing. It assumes you are generally familiar with network\n[MTU](/vpc/docs/mtu).\n\nCreate an auto mode VPC network\n-------------------------------\n\n### Console\n\n1. In the Google Cloud console, go to the **VPC networks** page.\n\n [Go to VPC networks](https://console.cloud.google.com/networking/networks/list)\n2. Select a project in the project pull-down menu.\n\n3. Click **Create VPC network**.\n\n4. Enter a **Name** for the network.\n\n5. Choose **Automatic** for the **Subnet creation mode**.\n\n6. Set the **Maximum transmission unit (MTU)**.\n\n For a VM to send and receive jumbo frames, the VM's virtual NIC needs\n to be connected to a VPC network with a MTU value that is as large or\n larger than the machine MTU. Set the MTU to the largest possible value\n for the VM, for example 8896. If you're using GPU machines, see\n [Jumbo frames and GPU machines](/compute/docs/network-bandwidth#jumbo-frames-mtu).\n7. Click **Create**.\n\nCreate firewall rules\n---------------------\n\n### Console\n\n1. In the Google Cloud console, go to the **Firewall policies** page.\n\n [Go to Firewall policies](https://console.cloud.google.com/net-security/firewall-manager/firewall-policies/list)\n2. Click **Create firewall rule**.\n\n3. Enter a **Name** for the firewall rule. \n\n This name must be unique for the project.\n\n4. In the **Network** pull-down menu, specify the name of the network you\n created.\n\n5. In the **Targets** pull-down menu, select **All instances in the\n network**.\n\n6. From the **Source filter** pull-down menu, select **IPv4 ranges**.\n\n7. In the field enter **10.128.0.0/16**.\n\n8. In **Protocols and ports** , select **Specified protocols and ports**.\n\n9. Check the **tcp** checkbox and enter **22** in the field.\n\n10. Check the **Other protocols** checkbox and enter **icmp** in the field.\n\n11. Click **Create**.\n\nCreate VMs\n----------\n\nThis section shows you how to create two VM instances for testing. \n\n### Console\n\nDo these steps twice to get two VMs in the same zone.\n\n1. In the Google Cloud console, go to the **VM instances** page.\n\n [Go to VM instances](https://console.cloud.google.com/compute/instances)\n2. Click **Create instance**.\n\n3. Specify a **Name** for your first VM.\n\n4. Click **Networking, Disks, Security, Management, Sole-tenancy**.\n\n5. Click **Networking**.\n\n6. In **Network interfaces** , click **default default (10.128.0.0/20)**.\n\n7. In the **Network** pull-down menu, select the network you created.\n\nConnect to VM instances using SSH\n---------------------------------\n\n### Console\n\n1. In the Google Cloud console, go to the **VM instances** page.\n\n [Go to VM instances](https://console.cloud.google.com/compute/instances)\n2. In the **Connect** column of your first instance, click **SSH**.\n\n3. In the **Connect** column of your second instance, click **SSH**.\n\nVerify MTU\n----------\n\n1. In the terminal for your *first* VM, run the following command:\n\n ```\n /sbin/ifconfig | grep mtu\n ```\n\n \u003cbr /\u003e\n\n The reported MTU should be `8896`. \n\n ```\n ens4: flags=4163 mtu 8896\n lo: flags=73 mtu 65536\n ```\n\n \u003cbr /\u003e\n\n2. In the terminal for your *second* VM, install `tcpdump`:\n\n ```\n sudo apt-get install tcpdump --yes\n ```\n\n \u003cbr /\u003e\n\n3. In the terminal of your *second* VM, start `tcpdump`. Replace\n \u003cvar translate=\"no\"\u003eFIRST_VM_NAME\u003c/var\u003e with the name of your first VM.\n\n ```\n sudo tcpdump host FIRST_VM_NAME -v\n ```\n\n \u003cbr /\u003e\n\n4. In the terminal of your *first* VM, ping your second VM. The ping command\n must specify a packet size that is 28 bytes smaller than the network MTU.\n Replace\n \u003cvar translate=\"no\"\u003eSECOND_VM_NAME\u003c/var\u003e with the name of your second VM.\n\n ```\n ping SECOND_VM_NAME -c 10 -M do -s 8868\n ```\n\n \u003cbr /\u003e\n\n5. Check your second VM. You should see something like the following:\n\n ```\n tcpdump: listening on ens4, link-type EN10MB (Ethernet), snapshot length 262144 bytes\n 19:43:57.116005 IP (tos 0x0, ttl 64, id 0, offset 0, flags [DF], proto ICMP (1), length 8896)\n FIRST_VM_NAME.c.PROJECT_ID.internal \u003e SECOND_VM_NAME.c.PROJECT_ID.internal: ICMP echo request, id 5253, seq 1, length 8876\n 19:43:57.116053 IP (tos 0x0, ttl 64, id 23961, offset 0, flags [none], proto ICMP (1), length 8896)\n SECOND_VM_NAME.c.PROJECT_ID.internal \u003e FIRST_VM_NAME.c.PROJECT_ID.internal: ICMP echo reply, id 5253, seq 1, length 8876\n ```\n\n \u003cbr /\u003e\n\n The variables mean the following:\n - \u003cvar translate=\"no\"\u003eFIRST_VM_NAME\u003c/var\u003e is a name of your first VM.\n - \u003cvar translate=\"no\"\u003eSECOND_VM_NAME\u003c/var\u003e is a name of your second VM.\n - \u003cvar translate=\"no\"\u003ePROJECT_ID\u003c/var\u003e is the ID of the project containing the VMs.\n6. On your second VM, press `Ctrl-c` to stop `tcpdump`.\n\n7. When you're done testing, delete your resources in the following order:\n\n 1. Firewall rule and VM instances\n 2. VPC network\n\nWhat's next\n-----------\n\n- Learn more about [MTU](/vpc/docs/mtu).\n- Create a [VPC network with a specified\n MTU](/vpc/docs/create-modify-vpc-networks#creating_networks)."]]
