I asked a question not too many hours ago about multiple router interfaces on one network, and I think I have now established what I need to do, however I do not understand how to implement it.

For me to be able to have multiple interfaces on one network, I need to have a switch HWIC, and the HWIC-4ESW seems to be what I need, however aside from having multiple interfaces on one network I also need to have more interfaces which I can assign different IP addresses to for multiple networks (the 2811 I am using is the only router I have and I use it with multiple startup-configs depending on what I an messing with).

This is where the root of the problem lies. As the HWIC-4ESW is a Layer 2 Switch HWIC, it is impossible to assign each port separately an IP address directly like you would the built in FastEthernet interfaces on the router. What you instead have to do is assign each port its own VLAN and then put an IP address on each VLAN. From what I can see, having each port on its own VLAN and assigning an IP to that VLAN makes the port 'technically' Layer 3, the VLAN giving the Layer 2 port the 'extra layer' so to say. If I want to then put multiple ports on the same network, I simply put two or more ports on one VLAN and assign that VLAN an IP address, 'technically' making 2 interfaces on the same network. Please, correct me if any information in this paragraph is wrong.

The main issue with the above paragraph is the actual creation of the VLANs. I wanted to simply put switchport mode access vlan 100 on each interface I want to be together, than assign an IP to the VLAN with interface vlan 100 ip address x.x.x.x however switchport does not work on a 2811 because quite obviously it's not a switch. Its a router. So does the switchport option and the interface vlan option become available when I install the HWIC-4ESW, or do I now have to start talking about subinterfaces...

From my original question, I see I may have to work with subinterfaces to assign VLANs to the ports on the HWIC-4ESW. And I haven't a clue where to even begin with this.

As a newbie I am picking things up fast, but with this I am completely stumped. I don't want to spend money on an HWIC-4ESW only to find I haven't a clue how to configure it the way I want it to work: In one instance as 4 separate 'technically' Layer 3 ports, and in the other assign two or more of its ports to a VLAN to have multiple interfaces on one network.

  • Incorrect config fixed in the other answer, sorry for misdirection. – jonathanjo Dec 16 '17 at 20:49

Your command, switchport mode access vlan 100 is incorrect. The correct commands are:

switchport access vlan 100
switchport mode access

Also, the HWIC modules for the 2811 are pretty limited in the maximum bandwidth on a WIC slot. You may want to look at something like a Cisco NM-16ESW module for your router.

Edit for your comments:

Your router interfaces cannot be configured as switch interfaces, so the switchport interface command is not available on them. If you add a switch module, then you can use the switchport command on the switch interfaces, although the switch modules for the router are limited to basic switching functions. They cannot do any of the advanced switching features, e.g etherchannel, or be configured as router interfaces.

You will be able to create SVIs, e.g. interface Vlan100, and assign the switch module interfaces to VLANs, or as trunks for multiple VLANs.

  • That NM-16ESW looks quite nice, and it seems it can be used in both a Layer 2 and Layer 3 way, so I can assign the ports to VLANs OR I could directly assign IPs, correct? And with those corrected commands: My point is switchport isn't even recognised on my 2811, so will it become recognised when I install a HWIC-4ESW or NM-16ESW and try to configure their interfaces? – DevelopedLogic Dec 16 '17 at 20:37
  • The NM is a layer-2 module, with switch interfaces, not router interfaces. The 2811 will have the switchport command if you have a switch module installed. It is a switch interface command, and if you don't have any switch interfaces, then you have no place to try to configure it. – Ron Maupin Dec 16 '17 at 20:40
  • Okay! This is definitely starting to make more sense now! So If I buy a NM-16ESW or HWIC-4ESW and install them, their ports will appear as interfaces such as FastEthernet1/1, FastEthernet1/0 etc and when I try to configure those interfaces I will be able to use the switchport access vlan xxxx option? And when I have done that switchport on at least one Layer 2 interface for example switchport access vlan 100 I will then be able to interface vlan 100 and configure that VLAN? If so please post an answer with the information compiled together so I can give you credit. – DevelopedLogic Dec 16 '17 at 20:44
  • @DevelopedLogic, the way the ISR routers, like your 2811, are designed are to use the built-in ethernet interfaces for your LAN (connect to a switch), or with a switch module. The switch modules you install in the router are pretty limited to basic switching functions (no etherchannels, etc.). The WIC slots are what you would use for WAN connections (WIC stands for WAN Interface Card). You can get an ethernet router card for your WIC slots (e.g. HWIC-1GE-SFP), but the WIC slots are limited to something like 350 Mbps. – Ron Maupin Dec 16 '17 at 20:45
  • I'm not too concerned with speed. I'm more concerned with money I am spending. If all the switchport and VLAN stuff I mentioned in my previous comment works as I explained, i'm a happy person. If it does work how I explained when i'll probably get a NM-16ESW. – DevelopedLogic Dec 16 '17 at 20:50

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