Switch on Ricky

Google Infra

Tue, 24 Sep 2024 09:04:00 +0800

Google’s 5-generation network architecture in ten years

Switch Firmware Update

Thu, 14 Jun 2018 12:28:29 +0800

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:
1. 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

How to Enable SNMP on a Switch

Sun, 04 Feb 2018 14:48:12 +0800

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

Switch notes

Sat, 25 Nov 2017 11:47:37 +0800

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