# Setting Router Clocks in Cisco Devices

In this lesson, I'll guide you step by step on how to set the clock on a Cisco router. This is an essential task in networking, as an incorrect time setting can impact logging, authentication protocols, and network synchronization.

### <mark style="color:blue;">**Step 1: Understand the Importance of Router Clock**</mark>

Before we start configuring, let's understand why setting the correct time on a router is important:

* **Accurate Logging:** Ensures that logs have the correct timestamps.
* **Security Protocols:** Some authentication mechanisms depend on synchronized clocks.
* **Network Management:** Helps in troubleshooting and performance monitoring.

Cisco routers do **not** have a built-in battery-backed clock like computers. They lose their time setting when rebooted unless a **Network Time Protocol (NTP)** server is used.

### <mark style="color:blue;">**Step 2: Check the Current Clock Setting**</mark>

To check the router's current date and time, use:

Router# show clock

```bash
Router#show clock
*14:30:33.211 UTC Mon Mar 31 2025
Router#
```

The asterisk (`*`) indicates the clock is not set.

### <mark style="color:blue;">**Step 3: Manually Set the Clock**</mark>

You can manually set the clock using the following command:

```bash
Router#clock set ?
  hh:mm:ss  Current Time

Router#clock set 18:01:00 ?
  <1-31>  Day of the month
  MONTH   Month of the year

Router#clock set 18:01:00 31 ?
  MONTH  Month of the year

Router#clock set 18:01:00 31 March ?
  <1993-2035>  Year

Router#clock set 18:01:00 31 March 2025
Router#
*Mar 31 18:01:00.000: %SYS-6-CLOCKUPDATE: System clock has been updated from 14:32:20 UTC Mon Mar 31 2025 to 18:01:00 UTC Mon Mar 31 2025, configured from console by console.
Router#
```

**Breakdown of the command:**

* `14:30:00` → Time in 24-hour format.
* `31` → Day of the month.
* `Mar` → Three-letter abbreviation for the month.
* `2025` → Year.

### <mark style="color:blue;">**Step 4: Verify the Clock**</mark>

After setting the clock, verify it using:

```bash
Router#show clock
18:02:27.855 UTC Mon Mar 31 2025
Router#
```

### <mark style="color:blue;">**Step 5: Set the Time Zone**</mark>

By default, the router uses **UTC (Coordinated Universal Time)**. To set your local time zone, use:

```bash
Router(config)#clock timezone ?
  WORD  name of time zone

Router(config)#clock timezone IRST ?
  <-23 - 23>  Hours offset from UTC

Router(config)#clock timezone IRST 3 ?
  <0-59>  Minutes offset from UTC
  <cr>

Router(config)#clock timezone IRST 3 30 ?
  <cr>

Router(config)#clock timezone IRST 3 30
Router(config)#
Mar 31 18:05:10.123: %SYS-6-CLOCKUPDATE: System clock has been updated from 18:05:10 UTC Mon Mar 31 2025 to 21:35:10 IRST Mon Mar 31 2025, configured from console by console.
Router(config)#
```

### <mark style="color:blue;">**Step 6: Save the Configuration**</mark>

Since Cisco routers **lose time** when rebooted, you need to configure **NTP** or manually reset the clock after every restart.

To save the configuration:

```bash
Router#write memory
Warning: Attempting to overwrite an NVRAM configuration previously written
by a different version of the system image.
Overwrite the previous NVRAM configuration?[confirm]
Building configuration...
[OK]
Router#
```

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