Why IP overlapping?

[alextech1]

I'm trying to do a lab in PT. and get the following error:

FIRST Router(config)#int G0/0
Router(config-if)#ip add 192.168.0.1/30
Router(config-if)#exit
SECOND Router(config)#int G0/0
Router(config-if)#ip add 192.168.0.2/30

NOW, ON THE SECOND ROUTER I TRIED CONNECTING A SWITCH connected with 5 PCs

SECOND Router(config)#int G0/1
Router(config-if)#ip add 192.168.0.5/29
% 192.168.1.0 overlaps with GigabitEthernet0/0

The last Valid IP Address for 192.168.1.0 is 192.168.3. The next subnet is 192.168.0.4.
Why is overlapping when I'm using /29 with Valid host from 192.168.1.5 to 192.168.1.11 which doesn't fall in the range of /30 192.168.1.1 to 192.168.1.3?

[Philip D'Ath · Accepted solution]

192.168.0.0/29 runs from 192.168.0.0 to 192.168.0.7 (it does not starts at 192.168.0.5).  The next block starts at 192.168.0.8/29.  So it is indeed overlapping.

So the second router needs an IP address of 192.168.0.9/29.

[Philip D'Ath]

If you use windows then this is a good subnet calculator:

http://www.solarwinds.com/products/freetools/free_subnet_calculator.aspx

On Linux a good tool is ipcalc.

[alextech1]

Thank you so much. I'm new to the whole subnetting. Trying to understand as much as possible before trying to use any Calculators. I see my confusing.

I thought because R1 ended at 192.168.1.3 and next Subnet was 192.168.1.4, I could use 192.168.1.5. Not realizing that /29 Still covered from 1-7. I fixed the problem by making My G0/1 Ip Address 192.168.1.9 connected to the which with is connected to the  5 hosts.

Host 1 = 192.168.1.10

Host 2 = 192.168.1.11

Host 3 = 192.168.1.12

Host 4 = 192.168.1.13

host 5 = 192.168.1.14

[joepeeer]

thnk u

[Tanvir Rashid]

If you use an IP address in your and return you assign the same IP address in your network this time you can see the overlapping massage... This call overlapping and you can't apply this IP address in your network. In this case, you need to check the IP address in your network and assign a new IP in the network .... thanks a lot...

[mad_mavula]

When you configure an IP address on an interface, the router will add the network of that IP address as a connected route. You will see that by executing "show ip route" . But when you are trying to configure an ip address of the same previous subnet (connected route) but on a different interface the router gets confused since for the same connected route we are trying to introduce two different interfaces.

[jaura512]

Hello,
can anyone explaine this overlapping with the same mask please?

Edmonton#conf t

Enter configuration commands, one per line. End with CNTL/Z.

Edmonton(config)#int

Edmonton(config)#interface g

Edmonton(config)#interface gigabitEthernet 0/0

Edmonton(config-if)#ip add 172.16.10.1 255.255.0.0

Edmonton(config-if)#no sh

Edmonton(config-if)#

%LINK-5-CHANGED: Interface GigabitEthernet0/0, changed state to up

%LINEPROTO-5-UPDOWN: Line protocol on Interface GigabitEthernet0/0, changed state to up

Edmonton(config-if)#exit

Edmonton(config)#int

Edmonton(config)#interface gi

Edmonton(config)#interface gigabitEthernet 0/1

Edmonton(config-if)#ip add 172.16.20.1 255.255.0.0

% 172.16.0.0 overlaps with GigabitEthernet0/0

Edmonton(config-if)#