CISCO VLAN's Router On A Stick Method

Hi Guys,

I have just started looking into CISCO and the first thing that I would like to achieve is VLANS. I have found all the commands to do what I want to do when I config the switch through the console port, but it seems that CISCO have changed some of the commands since one of the youtube vids I was watching.

What I want to be able to do is setup VLAN 1, 2 and 3 lets say:

I want to stop VLAN 1 and 2 talking to each other but would like them to be able to see and talk to VLAN 3.

I have managed to look up Router on a stick which is very similiar to what I am trying to achieve but most of the tutorials allow VLAN 1 and 2 to talk between each other.

I was wondering maybe if someone knew all the commands I needed to get this up and running?

Thanks in advance
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m_walkerConnect With a Mentor Commented:
By default all vlans will be able to see each other.  You have three choices.
1. User an external firewall and use those ACLs (could be an over kill and slow things down a little)
2. Policy Based Routing - where acls are used to allow packets to go between vlans
3. VRF and limit routing tables (and ensue you dont use you common vlan as the default gateway else the other 2 will route via the common one.

I dont have a quick example of PBR but it should be the simplest.  I generally find the PBR is slow and use a firewall (as simple linux box with ip tables was faster then my 3750E PBR setup.  My ACS firewall as faster then PBR.

VRF is good, but wont work if you need to route via the common vlan to the net.
ffleismaConnect With a Mentor Senior Network EngineerCommented:
you can use access list to block traffic between VLAN 1 & VLAN 2. what cisco router are you using? and what switch? I'll be glad to help you out on the config.
dan4132Author Commented:
Hey Guys,

Thanks very much for your input. So I guess ACL's is the way forward with this.

I have:
1 x Cisco Catalyst 3550 Switch (I mainly use this one over the 2950)
1 x 2950 Switch
1 x 2621 Router

Any help would be appreciated :)


Craig BeckConnect With a Mentor Commented:
If you're doing router-on-a-stick just put an ACL on each interface.

Something like this (off the top of my head)...

interface fa0/0.1
encapsulation dot1q 1
ip address
ip access-class 101 in
interface fa0/0.2
encapsulation dot1q 2
ip address
ip access-class 101 in
interface fa0/0.3
encapsulation dot1q 3
ip address
ip access-class 101 in
access-list 101 deny ip       (Blocks access from Vlan1 to Vlan2)
access-list 101 deny ip       (Blocks access from Vlan2 to Vlan1)
access-list 101 permit ip any any                                                               (Allows everything else)
dan4132Author Commented:
Will Close
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