Configure Cisco router as DHCP client

Remember, SOHO devices are configured as DHCP clients by default. When you are DHCP client to your ISP you need to configure interface on enterprise device to receive IP address.

I have created topology as it is shown in Slide 1.

option33_1

Slide 1.

ISP router is configured as DHCP for 192.168.100.0/24 network with 192.168.100.1 on Fa0/0.

On ISP_Client router you need to enable Fa0/0 to be DHCP client. Please, configure your router as follows:

ISP_Client(config)#interface FastEthernet0/0
ISP_Client(config-if)#ip address dhcp

First verify that you recieved IP address with show ip interface brief. My output looks like this:

ISP_Client#show ip interface brief
Interface              IP-Address      OK? Method Status                Protocol
FastEthernet0/0        192.168.100.2   YES DHCP   up                    up
FastEthernet1/0        unassigned      YES unset  administratively down down
FastEthernet1/1        unassigned      YES unset  administratively down down
GigabitEthernet2/0     unassigned      YES unset  administratively down down

Notice that we have IP address on FastEthernet0/0. Now verify your routing table with show ip route:

ISP_Client#show ip route
Codes: L – local, C – connected, S – static, R – RIP, M – mobile, B – BGP
D – EIGRP, EX – EIGRP external, O – OSPF, IA – OSPF inter area
N1 – OSPF NSSA external type 1, N2 – OSPF NSSA external type 2
E1 – OSPF external type 1, E2 – OSPF external type 2
i – IS-IS, su – IS-IS summary, L1 – IS-IS level-1, L2 – IS-IS level-2
ia – IS-IS inter area, * – candidate default, U – per-user static route
o – ODR, P – periodic downloaded static route, H – NHRP, l – LISP
+ – replicated route, % – next hop override

Gateway of last resort is 192.168.100.1 to network 0.0.0.0

S*    0.0.0.0/0 [254/0] via 192.168.100.1
192.168.100.0/24 is variably subnetted, 2 subnets, 2 masks
C        192.168.100.0/24 is directly connected, FastEthernet0/0
L        192.168.100.3/32 is directly connected, FastEthernet0/0

Along with IP address you will “receive” default route to your ISP.

Dejan Dzodan

Dejan Dzodan

IT professional for more then 15 years, mostly in financial institutions but with experience in ISP and retail. Proven in networking and overall infrastructure projects. Cisco instructor.

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