conf t Archives : FATMIN

Sometimes when I learn something new in the world of technology, I am often amazed that something that I assumed was technically advanced is rather quite simple.

Such is the case with configuring DHCP on a Cisco Router. I mean, is it just me or do network guys sometimes act as if everything that they do is takes elite technical skills and tons of experience. Don’t get me wrong, I know that networking is not exactly easy. But can we just agree to admit that once in a while some things are easier done than said. Anyway, for me this was the case with configuring a DHCP pool on a Cisco Router.

In this instance I was working on getting a new virtual machine up and running on my ESXi host. This particular appliance needed to boot via dhcp so you could access its web interface. So I jumped on my 2621xm and created the pool.

First we enable the dhcp service

r-2621-1(config)#service dhcp

Then we create a pool

r-2621-1(config)#ip dhcp pool LabPool
r-2621-1(dhcp-config)#network 10.2.0.1 255.255.255.0

Next we set a few bits and bobbles so that clients can route.

r-2621-1(dhcp-config)#dns-server 10.2.0.71
r-2621-1(dhcp-config)#default-router 10.2.0.1
r-2621-1(dhcp-config)#domain-name localdomain

In this case I wanted to exclude a bunch of ips from the range

r-2621-1(dhcp-config)#ip dhcp excluded-address 10.2.0.1 10.2.0.100

Now save your config with copy run start.

The command below shows me all my dhcp clients

r-2621-1#show ip dhcp binding
Bindings from all pools not associated with VRF:
IP address Client-ID/ Lease expiration Type
Hardware address/
User name
10.2.0.101 0050.569a.7dbe Oct 16 2013 11:21 PM Automatic

This handy command shows me information pertaining to my pool

r-2621-1#show ip dhcp pool

Pool LabPool :
Utilization mark (high/low)    : 100 / 0
Subnet size (first/next)       : 0 / 0
Total addresses                : 254
Leased addresses               : 1
Pending event                  : none
1 subnet is currently in the pool :
Current index        IP address range                    Leased addresses
10.2.0.102           10.2.0.1         – 10.2.0.254        1
r-2621-1#show ip dhcp conflict

HomeLab: Simple Cisco EIGRP Setup

Cisco DHCP Client Lease Time

HomeLab: Simple SSH Setup on a Cisco Router

HomeLab: Cisco 2621 Router Password Recovery/Factory Reset

Configuring InterVLAN Routing on a Layer 3 Switch and providing DHCP to multiple subnets Part 1

First off let me say that its really good practice to configure ports one by one, at least when you are starting out in the network world, as the repetition of typing the same thing over and over helps you to remember the proper commands. Hell this is one of the reasons that I blog the stuff that I do… I'm trying to make sure that I do not forget what I just learned.

Anyway, this is a quick and dirty one that I cannot remember to save my life. In this instance I wanted to configure a few ports on a 2950 that I plan to use to replace my 2960, as my 2960 is destined for bigger and better things given its layer 3 capabilities.

Note the spaces between the first port in the range, the dash, and the last port in the range.

s-2950-1.localdomain(config)#interface range fastEthernet 0/9 – 16
s-2950-1.loc(config-if-range)#description vlan 1 ports
s-2950-1.loc(config-if-range)#switchport mode access
s-2950-1.loc(config-if-range)#switchport access vlan 1
s-2950-1.loc(config-if-range)#spanning-tree portfast

%Warning: portfast should only be enabled on ports connected to a single
host. Connecting hubs, concentrators, switches, bridges, etc… to this
interface when portfast is enabled, can cause temporary bridging loops.
Use with CAUTION

%Portfast will be configured in 8 interfaces due to the range command
but will only have effect when the interfaces are in a non-trunking mode.

s-2950-1.loc(config-if-range)#spanning-tree bpduguard enable
s-2950-1.loc(config-if-range)#end
s-2950-1.localdomain#copy run start