While performing routine configuration on a Cisco router, I encountered a funny typo. Try to find it by yourself. Hint: it’s in the last line.

In this tutorial we’ll learn :

• How to push an IOS image into a switch flash disk, using Cisco LMS,
• How to verify that the IOS image has been loaded correctly

Pushing the IOS image

1. On the LMS home page, click on the Resource Manager Essentials link.

2. Click on Software Distribution

3. Choose a distribution method. By default, I use “by device”. That’s the simplest one

4. Check the device for which you want to upgrade the IOS and click Next

There are times when you want to schedule a router reload, but you don’t want to stay late or come to the office during weekends. “Reload at” is your friend.

How to reload your router at a predefined time

You want to reload your router (or switch) at 7pm, but at the same time, you’ll be having a coffee with your friend and you don’t want to have this discussion: “- Sorry guys, I have a router to reboot. I’ll be back in 30mn.

• a 3750 can act as a layer3 switch by adding the “ip routing” command.
• It can automatically route between locally created vlans because it considers them as connected interfaces (given that the SVIs are created).
• on a device, there are 3 types of traffic: control, management, end user.
• Control traffic such as CDP, DTP, PAgP goes through vlan1 between Cisco switches, even if you clear it from trunks.
• By default, native vlan traffic is untagged. But there’s a Cisco command that tells the switch to tag all vlans.
• by default, native vlan = vlan1. If we set the native vlan to vlan100, then vlan100 frames will be untagged on trunks, and vlan1 frames will be tagged.
• SMI: Standard Multilayer Image
• EMI: Enhanced Multilayer Image
• if switch is acting L2, then we should set a Default Gateway on it to make the management vlan reachable remote ; if it is acting L3, it will have routes instead.
• switch and Management vlan
• the management IP address must be reachable from remote
• best practice: use a same subnet to manage all network devices
• on L2 SW: only one SVI is up at a time

First, let’s see if QoS is enabled on the switch: QoS is disabled. We should enable it on global configuration level: If we want to display QoS settings for an interface, we do a show mls qos interface command: At this stage we still did not define trust boundaries. That’s why Trust State and Trust Mode say “not trusted”. And we did not specify whether we’ll trust a device or not. To define trust boundary with auto-qos, we either trust all CoS values coming on the switch interface or we trust CoS values only if an ip phone is connected to the switch port. With auto qos voip trust, we tell the switch to trust CoS on each packet coming on the switch interface: If we want to further limit trust boundary, we can tell the switch to trust CoS values only if a Cisco ip phone is detected on the port: Finally, on a 3550 switch, show auto qos and show auto qos interface give the same output:

Enabling Loop Guard on an interface level does not enable it for the whole system. In fact, a “show spanning-tree summary total” is a bit misleading in this case.

To configure loop guard on an interface:

“loop guard default” is disabled because we haven’t issued a “spanning-tree loopguard default”. Easy:

verify that QoS is enabled:

Enable QoS:

At this stage, all interfaces are by default untrusted. This means that any frame with a priority value will be remarked as CoS/IP Precedence/DSCP value = 0.

Trust CoS values of incoming frames. Useful for trunks:

Trust CoS values only if an attached Cisco ip phone exists (conditional trust):

At this stage, the trust boundary moves to the IP phone. Any priority value of any attached PC frames is untrused, thus remarked with priority 0.

In this lab, I learned the following:

• configuring a HSRP group on physical interfaces,
• testing how a PC can reach a remote subnet through a redundant gateway, by configuring its default gateway as the HSRP virtual address,
• testing how the second router becomes Active,
• testing interface tracking.

For interface tracking, at first, I thought there was a problem with the lab. Topology: configure interface tracking and a decrement value: When I shut down ser0/0 on R2, I expected R2 to become Standby router. But reality bites: Then I checked on R3. R3 is still Standby, not Active ! So what’s wrong? Here’s what Cisco says: How Object Tracking Affects the Priority of an HSRP Router