adding multiple subnets to the same VLAN

Oct 07, 2005 2 Replies
C

I think this is OK, but I wanted to run it past a few pros first.



I have an interface that looks like this:



interface GigabitEthernet0/0 description Cisco 3845 no ip address duplex full speed 100 media-type rj45 negotiation auto ! interface GigabitEthernet0/0.1 description HP Management VLAN encapsulation dot1Q 1 native ip address 10.10.5.1 255.255.255.0 no snmp trap link-status no cdp enable ! interface GigabitEthernet0/0.2 description Primary Data VLAN encapsulation dot1Q 2 ip address 10.20.5.1 255.255.255.0 no snmp trap link-status no cdp enable !



On VLAN 2, I am running out of address on that class C network. I want to add another class C to the same VLAN. I assume I can add a secondary address to the same VLAN to look like



interface GigabitEthernet0/0.2 description Primary Data VLAN encapsulation dot1Q 2 ip address 10.20.5.1 255.255.255.0 ip address 10.21.5.1 255.255.255.0 secondary no snmp trap link-status no cdp enable



Is this an acceptable method? Or have I crossed to the dark side.



Thanks, Chuck



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S

Chuck,

Technically, this will work. However, a better means of doing this would be somthing like:

ip address 10.20.5.1 255.255.254.0

This would give you a supernet of 10.20.4.1-10.20.5.254

You'd have to change the subnet mask on the workstations, but it makes for a better solution. And, actually, you have 2 more available addresses than the multiple subnets method.

Hope that helps,

Jim

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