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Cisco Switch Core Vlans Isolation

Cisco Switch Core Vlans Isolation

Cisco Switch Core Vlans Isolation


I have a network with three VLans, vlan2 is users, vlan 20 is server, and vlan 21 is public
I want vlan 21 to be isolated, from this vlan it should not be possible to access any device in vlan 2 and vlan20.
I have addeed this access list to the switch but i can still acess the devices from the other vlans but still i can access everything, can someone please point me what is wrong.

ip access-list extended OnlyInternet
permit udp any host eq bootps bootpc domain
deny ip any
deny ip any
permit ip any any

interface Vlan21
ip address
ip access-group OnlyInternet out
ip helper-address

RE: Cisco Switch Core Vlans Isolation

Either reverse soutrce and destination on each ACL line or (easier) change "ip access-group OnlyInternet out" to "ip access-group OnlyInternet in".

RE: Cisco Switch Core Vlans Isolation

if i change to in, all vlan stop having internet, and even with "in" using the public vlan i was able to access the server vlan. Really dont know what is wrong.

RE: Cisco Switch Core Vlans Isolation

It's been a while since I have used anything access list wise in this fashion, so may be a little rusty .....

ip access-list extended OnlyInternet - Name of access list
permit udp any host eq bootps bootpc domain - Permit UDP from Host that equals the elements described
deny ip any - Deny anything from network (IP based)
deny ip any - Deny anything from Network (IP based)
permit ip any any - Permit all other traffic

Then you are applying this list to the interface of VLAN 21

I may be wrong here, but the way you have the access list configured is saying "From" the 2 networks, but you are applying it to VLAN21.... those two deny lines, as far as I am aware, but could be wrong, are blocking traffic going out from those networks..... well, those networks don't exist.... only VLAN 21 does where you have applied it....

Surely you want to block traffic from those networks coming in or exiting, not saying they already exist as they don't. And they are basic commands.... for a standard access list, or could be.

Could you not create a standard access list and block traffic from VLAN 21 at the IN interfaces of VLAN 2 and VLAN 20?

Just a thought :)

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