I am trying to replace a linux router with a cisco 3745 router (IOS12.4) in a testbed. In my current linux configuration, I am able to create multiple subinterfaces on a single port. e.g. ifconfig eth1.0 10.0.10.1 netmask 255.255.255.0 ifconfig eth1.1 10.0.20.1 netmask 255.255.255.0 | ifconfig eth1.9 10.0.90.1 netmask 255.255.255.0
So I can connect 10 machines, each on a different subnet, to the linux router, using only a simple switch.
I would like to replace the linux router with a cisco router, but have not figured out how to create the subinterfaces on the cisco.
I thought I could do it by using a vlan switch and 802.1q on the port facing the router. The vlan1 tag 101 is applied to all the traffic I am interested in by the switch. On the switch, multiple ports, on multiple subnets, are members of that vlan.
However,starting with this:
interface FastEthernet0/1 no ip address duplex auto speed auto vlan-id dot1q 101 exit-vlan-config ! ! interface FastEthernet0/1.1 ! interface FastEthernet0/1.2
if I do this: RouterC#conf t Enter configuration commands, one per line. End with CNTL/Z. RouterC(config)#interface fa0/1.1 RouterC(config-subif)#ip address 172.16.10.254 255.255.255.0
I get this: % Configuring IP routing on a LAN subinterface is only allowed if that subinterface is already configured as part of an IEEE 802.10, IEEE802.1Q, or ISL vLAN.
How can I make it "part of an IEEE 802.10, IEEE 802.1Q, or ISL vLAN"?
I also tried this: However,starting with this:
interface FastEthernet0/1 no ip address duplex auto speed auto ! ! interface FastEthernet0/1.1 ! interface FastEthernet0/1.2
RouterC(config-subif)#encaps dot1q 101 native RouterC(config-subif)#ip addr 172.16.10.254 255.255.255.0 RouterC(config-subif)#inter fa0/1.2 RouterC(config-subif)#encaps dot1q 101
%Configuration of multiple subinterfaces of the same main interface with the same VID (101) is not permitted. This VID is already configured on FastEthernet0/1.1
Do I have to use a separate vlan for every subnet? If I do that it seems I would have to apply the tag at every host on the switch. All I want to do is get multiple different networks into one cisco interface, to replace the linux functionality.
Many thanks in advance for any help on this ,