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New Member

Pix520 as a VLAN policy router?

Can the PIX 520 function in the capacity of a simple ACL router? I.e., a default-deny policy with granular permit IP extended access lists.

There is some suggestion in the "Cisco Secure PIX Firewalls", Chapman/Fox that traffic can flow between multiple interfaces of the same security level but it is not a CCO-supported configuration.

I have multiple VLANs that I would like to setup very granular ACLs for and I do not want to assume one network has a higher security level than another.

interface ethernet0 100full

interface ethernet0 vlan1 physical

interface ethernet0 vlan10 logical

interface ethernet0 vlan20 logical

interface ethernet0 vlan21 logical

interface ethernet1 auto shutdown

nameif ethernet0 trunk security0

nameif ethernet1 inside security100

nameif vlan20 test0 security50

nameif vlan21 test1 security50

nameif vlan10 dmz security50

access-list 100 permit ip host host log

ip address test0

ip address test1

ip address dmz

access-group 100 in interface test0


If I ping from a host in Vlan2 at to (on dmz/vlan10), I get the following syslog:

106011: Deny inbound (No xlate) icmp src test0: dst dmz: (type 8, code 0)

Suggesting that an xlate/conduit/static/global command are needed, but NAT should not be a requirement.


New Member

Re: Pix520 as a VLAN policy router?

I just read about "Nat 0 Access-List" or NAT Excemption and added:

access-list no-nat permit ip

nat (test0) 0 access-list no-nat


I have the same results.


New Member

Re: Pix520 as a VLAN policy router?

You could configure it as an ACL filter, but need to configure NAT exemption to make it work

and you also need to allow communication between same security levels

New Member

Re: Pix520 as a VLAN policy router?

Yes, I saw that, except it's for 7.x only *and* the latest Pix OS that will run on a 520 w/ 16mb of flash is 6.3(5) (iirc).

Just to reitterate: I'm looking to do is enforce a "block all except ACL" policy. In the configuration at hand, there is no concept of a "DMZ", "WAN", "Inside", etc.

I *can* apply "nat (vlan#) 0 acl" with a different respective ACL to each interface using access-group, no problem, but I need the equivilant syntax for 6.x (unless there's some magic to getting 7.x on a Pix 520)

The release notes for 7.0(4) say 16mb flash min requirement, but they don't mentio the 520 at all (unless that's an attempt to marginalize it)

Version 7.0(4):