HomeLab: Simple DHCP Service Configuration on a Cisco Router

Cartoon-golfer-009Sometimes 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

Related articles

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Configuring InterVLAN Routing on a Layer 3 Switch and providing DHCP to multiple subnets Part 1
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HomeLab: Simple Cisco EIGRP Setup

Sugar_skull_by_nickgo79EIGRP (Enhanced Interior Gateway Routing Protocol), is a Cisco proprietary routing protocol (until recently). When a router runs EIGRP, it keeps a copy of its neighbors routing table. If I router cannot find a route it its, or its neighbor's routing table, it will query its neighbors who in turn query their neighbors.

Exactly how routing protocols work is serious business, but dont worry we are not going to go into that here. Below is the process that I used to setup EIGRP on a Cisco 2811.

Before we do anything, lets get into Configuration mode (conf t).

r-2811-1#conf t

 

Your first step is going to be to enable IP Routing on your device. But before you do so, make sure that you have configured a Gateway of Last Restort. I did not and had to hook up the old console cable.

The IP of this router is 10.1.0.2, and its directly connected to 10.1.0.1, which is its last resort first hop, so lets configure that .

r-2811-1(config)#ip route 0.0.0.0 0.0.0.0 10.1.0.1

 

Ok so now lets enable IP Routing

r-2811-1(config)#ip routing

 

Now lets start EIGRP and chose an AS number. Note that I used 10 on the other three routers in my setup so thats what we are going to use here.

r-2811-1(config)#router eigrp 10

 

Now we need to tell the router what networks are connected to it (or in this case, will be connected to it). This is the information that the router will share with its neighbors.

r-2811-1(config-router)#network 10.3.0.0

 

In this instance my ourside interface is on 10.1.0.0/16, and its inside interface will serve up 10.3.0.0./16.

Dont forget to save your work

r-2811-1#copy run start

 

Related articles

HomeLab: Simple SSH Setup on a Cisco Router
HomeLab: Cisco 2621 Router Password Recovery/Factory Reset
Hour 40: OSPF the new advanced link-state protocol
Route Redistribution: Protocol Rules + EIGRP Redistribution
Eigrp
Hour 31: IGP Review EIGRP