IP SINGLE CLASS /27

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Router

-

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interface FastEthernet0/0

no ip address

duplex auto

speed auto

!

interface FastEthernet0/0.1

encapsulation dot1Q 15

ip address 192.168.15.1 255.255.255.0

!

interface FastEthernet0/0.2

encapsulation dot1Q 20

ip address 192.168.20.1 255.255.255.0

-

---

Swicth 0

-

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interface FastEthernet0/1

switchport mode trunk

!

interface FastEthernet0/2

switchport mode trunk

!

interface FastEthernet0/3

switchport access vlan 15

!

interface FastEthernet0/4

switchport access vlan 20

!

vlan 15

name SALES

!

vlan 20

name SUPPORT

-

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Switch 2

-

---

interface FastEthernet0/1

switchport mode trunk

!

interface FastEthernet0/2

switchport access vlan 15

!

interface FastEthernet0/3

switchport access vlan 20

!

vlan 15

name SALES

!

vlan 20

name SUPPORT

-

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PC0

-

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IP: 192.168.15.2

mask:255.255.255.0

GW:192.168.15.1

PC1

-

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IP: 192.168.20.2

mask:255.255.255.0

GW:192.168.20.1

PC2

-

---

IP: 192.168.15.3

mask:255.255.255.0

GW:192.168.15.1

PC3

-

---

IP: 192.168.20.3

mask:255.255.255.0

GW:192.168.20.1

how can i change this IP address from two networks to a single networking using /27?

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Posted by WebUser Charalampos Skeleton C'trattou from Cisco Support Community App

[acampbell · Accepted solution]

Hi,

Reading your request I think you are aiming to use a /27 for
sales and a different /27 for Support

On your router - reconfigure like this:-

!
interface FastEthernet0/0.1
encapsulation dot1Q 15
no ip address
ip address 192.168.15.1 255.255.255.224
!
interface FastEthernet0/0.2
encapsulation dot1Q 20
no ip address
ip address 192.168.15.33 255.255.255.224
!
end

You will need to readdress your scopes in your
DHCP server if you use one.

Also readdress any static ip addressing your
PCs & printers etc.

Devices in Vlan 15

Ip addresses in the range 192.168.15.2-30
Mask 255.255.255.224
Defauly gateway 192.168.15.1

Devices in Vlan 20

Ip addresses in the range 192.168.15.34-62
Mask 255.255.255.224
Defauly gateway 192.168.15.33

Regards,
Alex.
Please rate useful posts.

[Richard Burts]

Alex

It is a possible interpretation of the question as being how to change from 2 networks with /24 to 2 networks with /27. But my reading of the original post suggests a different interpretation. I think that the original poster is asking how to combine into a single network which uses a /27.

If I have the correct interpretation then I would observe that the high level solution is fairly simple, though there may be a few complexities as they work through the process. Here is my suggestion of what needs to be done:

- multiple vlans require multiple networks. so if you want a single network then you need a single vlan.

- choose which vlan you will use.

- configure switch access ports in this vlan.

- remove the vlan that you will not be using.

- since there is a single vlan there is no need for switch ports. chane all ports currently configured as trunk to be access ports in the new vlan.

- with a single vlan/single network there is no need for vlan subinterfaces on the router. so remove the subinterfaces on the router.

- configure the router interface with an IP address and subnet mask for the new subnet.

- if there is DHCP to provide addressing information to clients then change the DHCP server to have a new scope for the new subnet. (and you can remove the old scopes)

HTH

Rick