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Google Infra

Google’s 5-generation network architecture in ten years

Tuesday, September 24, 2024 Read
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Switch Firmware Update

Preparation: Plug in the console. Copy the update file to the USB drive. Before starting, use show version to check the current version Update SOP: Insert the USB with the update file into the switch. The screen will show the detected device name. Copy the update file from USB to the switch flash: copy usbflash0(device name):<update-file> flash: Press Enter and confirm the file name, then press Enter again. A stream of ccccccccc means it is copying. After it finishes, use dir flash to verify the update file exists. conf t to enter config mode, then boot system flash:<update-file> to set the new IOS image. exit config mode, then show boot to confirm the new IOS is selected. write memory to apply settings to the running config. Run reload. It takes about 15-20 minutes. After it finishes, check the version to confirm the upgrade. copy usbflash0:cat.bin flash: copy usbflash0:cat.bin flash0-2: software install file flash:cat.bin switch 1-2 software clean

Thursday, June 14, 2018 Read
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How to Enable SNMP on a Switch

How to Enable SNMP on a Switch Use snmp-server as the main command. C3750(Config)#snmp-server community RO This is the shared secret for SNMP communication. RO means Read Only (SNMP tools are not allowed to modify settings). RW means Read and Write (SNMP tools can modify settings). C3750(config)#snmp-server group SNMP_ROA v3 priv match exact SNMP group name: SNMP_ROA Version: v3 Highest priv level C3750(config)#snmp-server user cater SNMP_ROA v3 auth MD5 cisco12345 priv des56 test12345

Sunday, February 4, 2018 Read
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Switch notes

Switch Switches are usually L2 devices They forward packets only to the destination host (based on the MAC table), which reduces collisions and eavesdropping. Switches can also handle packets arriving at the same time, while hubs cannot. Hubs are L1 devices They forward packets from any host to all connected hosts, so collisions happen and cause random retries. MAC Table Learning A packet arrives on some port (network A) from MAC X destined for MAC Y. The switch records that MAC X is on network A. This is called learning. Flooding The switch does not yet know where MAC Y is, so it forwards the packet to all networks except A. This is called flooding. Forwarding The host with MAC Y receives the packet and sends an ACK to MAC X. The switch records that MAC Y is on that network, then forwards the ACK to MAC X. This is forwarding. Filtering The switch receives a packet and finds that the source and destination MACs are on the same network, so it drops the packet. This is filtering. Aging Each MAC-table entry has a timestamp of last access. Entries older than a threshold (configurable) are removed. This is aging. Vlan Switch interfaces must support 802.1Q

Saturday, November 25, 2017 Read