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New Member

Different Subnets on the same Interface (FastEthernet)

Hello,

I have a quick question. Very basic. I have cisco 7206 and on FastEthernet which connects with Alcaltel switch can i configure two different ip subnets on an Interface.

Example :

cisco 7206

interface FastEthernet0/0

ip address 20.20.20.125 255.255.255.128 secondary

ip address 10.10.10.189 255.255.255.128

Now i have servers connected on different ports on the switch. Different subnets would be in different vlan. These are Alcatel switches so not sure what needs to be done on the switches.

But from the router perspective do i need to do anything.

Regards,

Hassan...

2 ACCEPTED SOLUTIONS

Accepted Solutions
Silver

Re: Different Subnets on the same Interface (FastEthernet)

Secondary IP addresses only work when both subnets are on the same VLAN. If you will have them on 2 VLANs on the switch, you'll need to set up a trunk between the Alcatel and the 7206 and configure it something like this:

interface FastEthernet0/0

description hosts on vlan 1 (native VLAN)

ip address 10.10.10.189 255.255.255.128

interface FastEthernet0/0.1

description hosts on Vlan 2

encapsulation dot1q 2

ip address 20.20.20.125 255.255.255.128

Cisco Employee

Re: Different Subnets on the same Interface (FastEthernet)

Hi Hassan,

Yes you are done with the configs on router. If you have differents IPs on same vlan you have to configure the way you described in your initial post.

HTH

Ankur

3 REPLIES
Silver

Re: Different Subnets on the same Interface (FastEthernet)

Secondary IP addresses only work when both subnets are on the same VLAN. If you will have them on 2 VLANs on the switch, you'll need to set up a trunk between the Alcatel and the 7206 and configure it something like this:

interface FastEthernet0/0

description hosts on vlan 1 (native VLAN)

ip address 10.10.10.189 255.255.255.128

interface FastEthernet0/0.1

description hosts on Vlan 2

encapsulation dot1q 2

ip address 20.20.20.125 255.255.255.128

New Member

Re: Different Subnets on the same Interface (FastEthernet)

Hello,

Thanks for the input. If different Ip's are on the same VLAN #, then all need to do is configure the way i described above ...right ??.I was just wondering if there is something extra i need to do.

Yes, you are right for different subnets on different vlans would need trunking..enaled to carry vlans on it.

Thanks,

Hassan

Cisco Employee

Re: Different Subnets on the same Interface (FastEthernet)

Hi Hassan,

Yes you are done with the configs on router. If you have differents IPs on same vlan you have to configure the way you described in your initial post.

HTH

Ankur

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