Questions about 881 Router

[Jeremy Strain]

I've been trying to teach myself vlans, IOS, and Cisco networking, so I bought an 881 Router, along with some older 3550 switches.  I'm very new to all of this, but it's been enjoyable to figure things out and play around with everything.

I've been successful in getting into each device and beginning to configure things, but I'm not sure if the 881 will let me recreate some of the examples I've come across.

Can the 881 perform Routing On A Stick?  Currently, I have the 881 just running as a typical router, with the WAN interface plugged into my existing home network.  The 2 3550 switches are plugged into fa1 and fa2 on the 881.  I've created a couple test vlans, and VTP (one of the 3550s is the server, the other switch and the 881 are clients) is updating them on the other devices.

Once I get into creating subinterfaces on the FA ports, I can't seem to do it on the 881.  It recognizes "int fa 1", but doesn't accept "int fa 0/1".  It's looking like the switch isn't layer 3, so I'm wondering if I can't run that setup with the 881.                  

[turnera]

Jeremy,

The 881 will not accept a 'fa 0/1' request because the fa ports are integrated into the router. What I mean by that is that they do not follow the slot/port/interface or slot/port convention that you see in other switches and routers. So the only way into the interfaces on an 881 is by entering the int fa0, int fa1, int fa2, int fa3 commands. You can create sub interfaces off of the main interface by entering into the main interface, int fa1.  And then creating the subinterface off of that (i.e. int fa1.1).

[Jeremy Strain]

Thanks for the reply!

I can't even seem to do that.  The best I can do is get to sub interfaces on fa4 (such as fa4.1, fa4.3, etc).  But that's the WAN port, so it doesn't help.

Am I stuck not being able to do Routing on a Stick with the 881?  Sorry if these are basic questions.  Trying to teach myself how to do all this and I haven't gotten very far yet.

[John Blakley]

The interfaces are configured as L2. Can you configure another port with "no switchport" and then try to do your subif?

Int fa3
No switchport
Int fa3.1
Encapsulation dot1q 20
Ip address x.x.x.c

I don't have access to one of these routers so is be I retested if this works.

Hth,
John

Sent from Cisco Technical Support iPhone App

[Jeremy Strain]

No dice.  If I try the "no switchport" command on any of the fa0 -  fa3 interfaces, it just returns "incomplete command".

I tried "no switchport mode".  That command goes through, but still can't create any subinterfaces. 

[Jeremy Strain]

I'm guessing it won't work because the 4 fa ports aren't L3.  Just want to verify that I can't make Router on a Stick work so that I don't keep wasting my time trying to make something work that never will 

[John Blakley · Accepted solution]

Are you dead set on using subinterfaces? Another way that you could do it is to create all of the vlans that you want, say 10, 20, and 30, and then create SVIs for those vlans. Then you could trunk the one port that connects to your 3550.

Something like the following:

int fa0

switchport trunk encapsulation dot1q

switchport mode trunk

int fa1

...

int fa4

int vlan 1

ip address (all of your other ports, 0 - 3, belong to this one by default)

Then create your other vlans:

int vlan 10

ip address ...

int vlan 20

ip address ...

int vlan 30

ip address ...

Then on your 3550, you'd create the same vlans and then trunk the port that connects to fa0 on this router.

*** Edit ***

I'm not sure if you'll have to, but you may have to create the vlans for these to attach to. In order to do that, from the (config) prompt, type "vlan 10" and then enter. It *should* create the vlan for you.

HTH,

John

**** Please rate useful posts *****

[Jeremy Strain]

Not tied to any particular method.  This is all just learning right now, so anything that works is useful.  I was interested in subinterfaces simply because they seem to be a necessary step in setting up Router on a Stick, which seemed like an easier way to get my feet wet with vlans.

VTP seems to have all my vlans mirrored between the devices, so that should be in order. 

I'll give a shot with the SVI method.  Thanks!

[Emmanuel Valdez · Accepted solution]

Hi Jeremy,

The 881 Cisco router only has 1 wan port, if you like to use subinterfaces you have to use these port but you lose the chance to connect an ISP, the other ports only support layer 2 features.

In this case you have to use SVI on the router and create trunk ports to the catalyst 3550.

Regards.


Sent from Cisco Technical Support Android App

[Jeremy Strain]

Thanks, everyone!  I somehow managed to get it all working tonight.  I'm not exactly sure how I did it, but clients on 192.168.10.x and 192.168.20.x are getting dhcp addresses, pinging each other, and can access the Internet.

Now I can at least work backwards from the run config and try to see exactly how it all fits together