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Blocking layer 3 traffic on a Cisco 3560-X switch

Posted on 2010-11-08
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Last Modified: 2012-06-21
I have a 3560X switch that I have routing turned on for and I would like to block all traffic from one specific vlan to all others. I have the following vlans:

VLAN 20 IP Address 10.2.0.14 255.255.0.0
VLAN 23 IP Address 10.23.0.1 255.255.0.0

I have ip routing turned on and I see routes.

I want to block traffic from vlan 23 to vlan 20 and I thought this would work:

access-list 101 deny ip 10.23.0.0 0.0.255.255 any
access-list 101 permit ip any any

vlan 20
ip access-group 101 in

I can still ping 10.2.0.14 from 10.23.0.100.

Ideas?
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Question by:lonekawboy
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Frabble earned 500 total points
ID: 34086836
The extended access list entries are source then destination.
Your list will deny anything from source 10.23.0.0/16, but you've applied it to incoming traffic on Vlan20 where the source addresses are 10.2.0.0/16, so nothing is blocked.

On Vlan23 you want to block any traffic to Vlan20 and allow any other, so:
access-list 101 deny ip any 10.2.0.0  0.0.255.255

or you could be specific and have:
access-list 101 deny ip 10.23.0.0  0.0.255.255  10.2.0.0  0.0.255.255

and then:
access-list 101 permit ip any any

interface Vlan23
 ip access-group 101 in
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Expert Comment

by:Don Johnston
ID: 34087248
Or you could use your existing ACL and apply it outbound on the VLAN 20 interface.
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Expert Comment

by:ciscocert
ID: 34087419
vlan 23 -> 20

access-list 101 deny ip 10.23.0.0 0.0.255.255 10.2.0.0 0.0.255.255
access-list 101 permit ip any any

int vlan 23
ip access-group 101 in



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LVL 50

Expert Comment

by:Don Johnston
ID: 34087708
Ciscocert:

Was it really necessary to post the exact same ACL that Frabble posted an hour earlier?
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