ISR 1100 DHCP and NAT Overload configuration on a /31

[Gattsun]

Hello,

I am a complete beginner in networking, started about a month ago. I was given a task to configure NAT Overload and DHCP on an ISR 1100 using a /31 subnet. Unfortunately I can't seem to find any guide on how to do this task as all instructions on pages are using multiple routers or ISP provided addresses while I have only one router and only the /31 address.

How am I supposed to configure this?
Sorry if this is a stupid question

[Georg Pauwen · Accepted solution]

Hello,

do you mean your router gets a /31 DHCP assigned IP address from your ISP ? If that is what you are asking, all you need to do is the below. The IP address you get from the ISP doesn't matter, as you are overloading the interface.

ip dhcp excluded-address 192.168.1.1

!

ip dhcp pool LAN

network 192.168.1.0 255.255.255.0

default-router 192.168.1.1

dns-server 8.8.8.8 8.8.4.4

!

interface GigabitEthernet0/0/0

description Link to ISP

ip address dhcp

ip nat outside

!

interface Vlan 1

ip address 192.168.1.1 255.255.255.0

ip nat inside

!

ip route 0,0.0.0 0.0.0.0 GigabitEthernet0/0/0 dhcp

!

ip nat inside source list 1 interface GigabitEthernet0/0/0 overload

!

access-list 1 permit 192.168.1.0 0.0.0.255

[Gattsun]

Hello,

I was just given an address by my boss and told to configure NAT and DHCP using it. What I meant was that while searching for solutions I came across multiple websites using an address provided by the ISP and I wasn't sure how to apply those to my situation.
Another question is the config you provided me with above going to allow me to configure Intranet and remote access using SSH as well?

Thank you for your time

[Georg Pauwen · Accepted solution]

Hello,

not sure what you mean by 'intranet'...can you elaborate ?

For SSH access, you need to configure the below:

hostname ISR1100
!
username admin privilege 15 password 0 cisco
!
ip domain-name yourdomain.com
!
crypto key generate rsa 2048
!
ip ssh version 2
!
line vty 0 4
transport input ssh
login local

[Gattsun]

I assume I got something wrong on the intranet part, I'll have to ask it over but thank you on everything else! You really helped me a lot!

Sometimes all of those guides make it seem so complex but you made it look so easy.

Thank you!