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New Member

vlan routing on a 3845


I need to setup vlan routing on a 3845 running 12.4 IOS. I have 4 Vlans

Vlan 2




I need to be able to route between all vlans from 2 to 20 to 50 to 100 and 100 to 50 to 20 to 2. How do I do this. Does anyone have a config to accomplish this?


Re: vlan routing on a 3845

Basically you want to use trunking to the switch and create subinterfaces on the router for each VLAN. The link below shows a great example of this. It is a little complicated to understand at first but realize that you use the router config for the trunk protocol you choose (ISL or 802.1q).

Hope this helps.


New Member

Re: vlan routing on a 3845

Which encapsulation type is better ISL or 802.1q. I have different vendor equipment in my network ie cisco, juniper-Netscreen and ISS-realsecure?

Re: vlan routing on a 3845

Does the router have ethernet switch module - show diag to confirm? I would have to assume that it does since you are talking actual vlan, if so all you need to do is configure the logical interface - interface vlan x - no shut it and by virtue of ip routing that the router is already doing it will route for the vlans. If no ethernet switch module then what you wanted to do is a "router-on-a-stick" where you configure subinterface on a fastethernet interface and encapsulate it with either dot1q or ISL. You will need at at least an IP Plus feature set this.

Hope that helps.

New Member

Re: vlan routing on a 3845

Here is the running config from the router.

Any suggestions?

Re: vlan routing on a 3845

With this configuration your PC in vlan 1 should be able to ping the PC in vlan 2 or 50 or etc? what kind of suggestion do you need?