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New Member

Controlling VLAN routing


We have 3550 L3 swicth and have configured three VLANs Viz : VLAN_A,VLAN_B,VLAN_C. With three different subnets as /24, /24 and /24. Plus there is one routed interface connected to firewall inside switch ( subnet /24) this is also a default route configured in L3 switch. What we need is that VLAN_B and VLAN_C shold not comminicate with each other. But should be able to communicate with default gateway. In short VLAN_B pc should not ping to VLAN_C and vice-a-versa.

Can it be implemented using VACL?

Private VLANs seems one option. But is there any option available? Can we just configure access-list like routers and apply it to vlan interface? So that it will act just like router interfaces so that any traffic originating from one VLAN and destined for another will hit this access-list and the corresponding action will be taken.

Please share any experience.

Any link on

Thanks in advance



Re: Controlling VLAN routing

Any of your options should work. The L3 ACL probably has the most overhead so don't forget about that. Here's a link that might help.

New Member

Re: Controlling VLAN routing

Hi ,

Use "switch port protected" on all server ports to prevent them from talking to each other.

Another ugly way would be to use vlan maps to filter ARP.

mac access-list extended MACL

permit any 0x806 0x0

permit any 0x806 0x0

mac access-list extended DROP

permit any any 0x806 0x0

vlan access-map block-arp 10

action forward

match mac address MACL

vlan access-map block-arp 20

action drop

match mac address ARP-DROP

vlan access-map block-arp 30

action forward

vlan filter block-arp vlan-list 10,20,30

Please note that methods mentioned above are locally significant, unlike pvlans.


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