Cisco CCNP SWITCH 642-813

Campus Security: VACLs

by Jeremy Cioara

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Welcome to Cisco Switch: Watch Me First!

The Switches Domain: Core Concepts and Design

VLANs: Configuration and Verification

VLANs: In-Depth Trunking

VLANs: VLAN Trunking Protocol

STP: Foundation Per-VLAN Spanning Tree Concepts, Part 1

STP: Foundation Per-VLAN Spanning Tree Concepts, Part 2

STP: Rapid Spanning Tree Concepts and Configuration

EtherChannel: Aggregating Redundant Links

L3 Switching: InterVLAN Routing Extraordinaire

L3 Switching: Understanding CEF Optimization

Redundancy in the Campus: HSRP, VRRP, and GLBP Part 1

Redundancy in the Campus: HSRP, VRRP, and GLBP Part 2

Campus Security: Basic Port Security and 802.1x

Campus Security: VLAN and Spoofing Attacks

Campus Security: STP Attacks and Other Security Considerations

Campus VoIP: Overview, Considerations, and AutoQoS

Wireless LAN: Foundation Concepts and Design Part 1

Wireless LAN: Foundation Concepts and Design Part 2

Wireless LAN: Frequencies and 802.11 Standards

Wireless LAN: Understanding the Hardware

The Switches Domain: Additional Life-Saving Technology

Monitoring: Your Pulse on the Network

Campus Security: VACLs

00:00:00 - We've come to this nugget, with one objective in mind: and that
00:00:04 - is to understand this concept of VACLs. Now everybody love's
00:00:09 - Access List. I know some of you are like: "Well, I don't love
00:00:12 - Access List". Well, the more you are in Cisco, the more you are
00:00:15 - like, "well, they are kind of fun, they are pretty cool", "kind
00:00:18 - of bend your mind a little bit in logic and all that kind of
00:00:20 - stuff". Cisco found a way to take an access list and apply it
00:00:24 - to a VLAN, and they called it a VACL. Now, if
00:00:28 - I were putting together a Cisco Certification Program for Switching,
00:00:32 - me Jeremy Char, personally was doing it, I would have probably
00:00:36 - left VACLs off. Simply because it is one of those concepts that
00:00:40 - you are going to see, you are going to look at it, and be like:
00:00:42 - "Ok, it is kind of cool, but I am not too sure where I would
00:00:45 - use that". And I would say, I have actually learned, and relearned,
00:00:51 - and relearned VACLs many many times, and it is primarily to study
00:00:54 - for a Certification Exam, just because when you get to the real
00:00:57 - world, it is not something I have seen used very often. I am
00:01:00 - not saying you would not be able to find a situation where you
00:01:03 - would use it, it is just not something I have seen been done
00:01:06 - very often. So with all that being said, I did not write the
00:01:10 - Cisco Certification Program, and someone else did, so they have
00:01:12 - decided to add VACLs, and they even went a step further...and
00:01:15 - as a matter of fact, if I just grab my pen here...They also added
00:01:18 - something on there called
00:01:21 - PACLs. You might have said, "This is just getting silly". It
00:01:24 - kind of is. It is P-A-C- L. It actually stands for Port Access
00:01:29 - Control List. What it is, it is simply applying an Access List,
00:01:34 - whether be a MAC Address Access List, or an IP Access List, to
00:01:38 - a layer two switch board. Which previously was not possible,
00:01:41 - and in the old days before multi-layer switching came about.
00:01:45 - So I though the best way to talk about VACLs and PACLs would
00:01:51 - just be to talk about them through a demonstration to show them
00:01:54 - to you. Here is the idea; A VACLs filters the entire VLAN landscape.
00:02:00 - So let's say we got this switch right here, and I just came up
00:02:03 - with a simple scenario, it got two VLANs: 10 and 30. And now
00:02:06 - I want to set it up in such a way that, VLAN 10 only allows
00:02:13 - the 10.1.10.0
00:02:15 - subnet. That means that if anybody plugs in...let's say for example,
00:02:19 - this guy right here plugs into the network on VLAN 10, "click"
00:02:21 - the network cable attaches, and he has the statically assigned
00:02:26 - address 192.168.1.1
00:02:30 - As soon as he tries to get into that VLAN, essentially the network
00:02:33 - landscape, he will be blocked, denied and restricted by this
00:02:36 - VACL that has been applied. That's the idea of VACLs, is that
00:02:40 - they apply to that entire landscape. I said, it is typically
00:02:43 - found in larger environments, some because it originated as a
00:02:47 - feature of the 6500 Switch. Now, the 6500 has the capability
00:02:53 - that my little 3550 here does not have. And that is the ability
00:02:57 - to use a VACL to redirect traffic. Now this would be a good use
00:03:02 - for it. In my opinion, it is probably the more popular use for
00:03:05 - it. Essentially you can go in, and create a VACL, in the same
00:03:10 - way right here, that says: "I want to match this subnet on VLAN
00:03:15 - 10, and I want to redirect that traffic to, we'll say, an IPS
00:03:20 - Sensor, and IDS Blade that allows you to sort through, and filter
00:03:25 - all that traffic through your security parameters. In this example,
00:03:28 - your VACL could even grab, you know, all traffic and just redirected
00:03:31 - it, filter out to an IPS Sensor, or maybe you have a DMZ VLAN,
00:03:35 - or something like that, you might want to do that, it's always
00:03:37 - very handy. The lower level switches, like my 3550, only allows
00:03:42 - you to use a VACL to permit and deny. Which again, is kind of
00:03:45 - cool, it is a neat feature, so let's talk about, let's work through
00:03:50 - this example. (Just let me get rid of all my gibberish here). Here
00:03:54 - is how it works: I am going to go Switch A, and literally create
00:03:58 - 2 VLANs. Let me bring my screen here. So we got the Switch.
00:04:03 - Go to Global Config. Mode, and I am going to do VLAN 10 and VLAN
00:04:09 - 30. Show VLAN.
00:04:13 - So we go, and we got a couple of them that were hanging out in
00:04:16 - the VLAN database, but VLAN 10 and VLAN 30 are definitely in
00:04:19 - there. So they are now created. And the scenario that we are
00:04:23 - working through says: "Ok, we've got clients on VLAN 10, and
00:04:26 - they should be restricted to the 10.1, 10.0. So no other IP address
00:04:30 - should be able to use on that subnet, or on that VLAN, other
00:04:34 - than this specific subnet. Same thing for VLAN 30, you got the
00:04:37 - subnet right here. Now, the way VACLs work are very similar to
00:04:43 - Route Maps. If you deal with Route Maps before on Routers, or
00:04:47 - you could even go on layer-three switch, they kind of a little
00:04:52 - programming language where you have sequence numbers. I always
00:04:54 - compare them to basic programming and an old commodore amigo computer
00:04:57 - but, you can have Line 10, Line 20, Line 30, kind of process
00:05:01 - through an order, one by one. So let me how I would have accomplished
00:05:05 - this scenario right here. Go
00:05:07 - to Global Config. Mode, first thing I would do is: Create a couple
00:05:11 - of Access Lists, to match these parameters. So I would say, VLAN
00:05:16 - 10, is going to match 10.1.10.0, so I am going to use, access-list;
00:05:23 - one; permit; 10.1.10.0;
00:05:28 - this is my master mask. Done. Very simple Access List, and is
00:05:32 - only filtering based on the source, because that's what the scenario
00:05:37 - requires. That only these sources should be allowed on that subnet.
00:05:41 - Now you can use an extended Access List with VACLs, that's not
00:05:44 - a problem, you can even use a Mac Address Access List. For example,
00:05:47 - I can go in here, and say...Mac,
00:05:51 - Access List...then we'll just say, this is an extended Access
00:05:56 - List; then I'll say the name of this is...we'll
00:06:00 - say Server.
00:06:03 - Now I can go underneath that, and use a Permit setting; Permit,
00:06:06 - we'll say "Any source Mac Address to access the destination 111"...well,
00:06:12 - actually I don't want to use a wildcard, so I'll put Host,
00:06:14 - 1111.1111.2222. Ok, so that's the Server. And that would
00:06:18 - be creating a Mac Address Access List, so I can say; this VLAN
00:06:22 - will only allow people to access that one destination Mac Address.
00:06:26 - Now again, you are probably looking at it, just like I am right
00:06:28 - now, and going "Wow, that's pretty cool! SO you are saying Jeremy,
00:06:31 - that I could create a VACL that only allows people to access
00:06:34 - one Mac Address?" Again, pretty neat. But again, unfortunately,
00:06:38 - I know...well, I don't know but I would assume that if you are
00:06:41 - like me, and get done with this nugget, and be like "Ok, I am
00:06:44 - ready for the exam", or for whatever you are going to apply this
00:06:47 - knowledge to, but then a couple of weeks after the exam, you
00:06:50 - will have forgotten, because, again, I haven't found a great
00:06:54 - use for this, where I am like "Oh, VACLS are so so amazing! That's
00:06:59 - kind of a buzz killer; I should come up with a great
00:07:03 - story. Well, it's too late. I've never used it in production,
00:07:07 - I'm just being honest. So, let's get back to our scenario.
00:07:13 - So, let me now go back to my #do show access list-1.
00:07:19 - So there's my 2 access lists. I need to create one more access
00:07:22 - list, we'll say #access-list
00:07:26 - 2 permit 10.1.30.0
00:07:31 - 0.0.0.255. Now I have my two access lists, one for each VLAN.
00:07:38 - So here's where the VACL comes in, and I will say that the syntax
00:07:40 - is not...I mean, once you use it for a while, it's ok, but it's
00:07:44 - not friendly to start with. You actually create something called
00:07:48 - a VLAN access map. So I'm going to type in #vlan access-map.
00:07:54 - Now again, if you've dealt with route maps, think exactly that
00:07:57 - same thing. When I do access map, it's going to ask me for a
00:08:00 - name, and I will say this is DEMO, we'll just name it, a case
00:08:04 - sensitive name, would you need that? And I will say here's my
00:08:09 - sequence number. So, I'll just start with sequence number 10,
00:08:12 - which if I just hit into it, would just be the default. And just
00:08:16 - like a route map, I'm going to have my match in action statements.
00:08:19 - So instead of match in set, if you've dealt with route maps,
00:08:22 - we have match and then action. What do you want to do with it? So,
00:08:25 - I'll say #match ip address
00:08:29 - and we'll say that this is match access list 1. This would be
00:08:33 - for VLAN...10...actually,
00:08:38 - I should have named this differently, but you've got the concept.
00:08:41 - We've got VLAN 10, so I'm going to say #match access list 1,
00:08:44 - which is the ip address in VLAN 10, and the action will be forward
00:08:52 - (#action forward). You're catching that? Now what's that doing?
00:08:55 - Let me go back here and just do a show run slash include.
00:09:01 - Let's just do begin with
00:09:04 - (#show run begin | vlan access-map).
00:09:11 - So right there we've got our VLAN access-map DEMO 10 that says
00:09:15 - if it matches the ip address. The source address is to find an
00:09:21 - access to this one, which we know are the 10.1.10. subnet. Then
00:09:26 - go ahead and forward it. So, I can then go, this is not necessary,
00:09:29 - because if you don't permit something, it will by default be
00:09:32 - denied. But just to show you how much like route map these are... I'm
00:09:35 - going to add another sequence number, we'll say DEMO 20. And
00:09:38 - I'll just say #action drop. You might say "What
00:09:45 - did that match?", as you don't have any match statement. Remember,
00:09:49 - it's just like a route map, if there's no match statement, then
00:09:52 - it's going to match everything. So again, walking through this
00:09:54 - demo access map, says sequence number 10 if it's these guys for
00:09:59 - them. However, if you're anything else, meaning that there's
00:10:02 - no match statement, then you will be dropped. So, once this is
00:10:07 - done, it's just like creating a route map, it doesn't take a
00:10:09 - fact until you apply it somewhere. So when you go back to the
00:10:13 - global config mode, I'm going to apply using the VLAN filter
00:10:17 - command. So, say #vlan filter and you'll say "What is the VLAN
00:10:21 - map name?" and I'll say the map name is DEMO. I'm going to apply
00:10:25 - that to the VLAN list, and that's where I can put my VLANs in.
00:10:29 - So this is just for VLAN list 10. But you can see that we can
00:10:32 - put in multiple VLANs, like VLANs 10 through 20, or VLAN 10 comma
00:10:37 - 30, comma 90. Those kind of things, it's totally fair game to
00:10:41 - apply it to anything or all VLANs. Now we'll allow filter VLAN
00:10:45 - 10. Now what about VLAN 30? Same kind of thing. We've already
00:10:50 - got the access list
00:10:54 - created forward, access list number 2.
00:10:57 - So I will create another access map, I'll say #vlan access-map
00:11:02 - and I'll just call this one DEMO1
00:11:05 - and we'll use sequence number 10. Same kind of thing. #match
00:11:09 - ip address 2 #action
00:11:12 - forward #exit Let's just add sequence 20. And I'll say #action
00:11:18 - drop. If you're looking for a nice concise demo of all of those
00:11:23 - things put together, I can then go on and say #vlan filter
00:11:28 - DEMO1. It's going to be the name of the access map. The VLAN
00:11:32 - I'm going to apply to is VLAN 30. Enter, done. So that's allowing
00:11:39 - you to apply
00:11:40 - access list to an entire VLAN landscape and filter these specific
00:11:47 - subnets to be allowed on those. Now again, this is just a very
00:11:51 - simple demonstration, so that you can see VACLs, see how they're
00:11:54 - used, but keep in mind that you can use extended access lists,
00:11:59 - you can use MAC address accesses, you can combine them all together
00:12:01 - with an access map. So there's all kinds of different ways that
00:12:05 - this can be applied, that just being one of them. Now while we're
00:12:10 - all here, I don't have a scenario for it, because it's very simple.
00:12:13 - I want also to add one more piece on the good old PACLs. Remember,
00:12:17 - I was saying we have VACLs, which is an access list applied to
00:12:20 - a VLAN, and we have PACLs, which is really just an access list
00:12:25 - applied to a port. Now the reason they came out with the specific
00:12:28 - name PACL and they didn't just call it an ACL, is because this
00:12:33 - is applying an ACL 2 layer 2 port. Now, if this is a layer 3
00:12:38 - port, you know, you get there by going the no switch port command,
00:12:43 - and you're applying an access list to it, it's not called a PACL,
00:12:47 - it's just an AXL, an access list, it's an ACL. Around an access
00:12:50 - list, it's applied to a layer 3 interface. But once it's a layer
00:12:53 - 2 interface, you can apply a PACL. Now the catch is PACLs, it's
00:12:57 - fun to say. It can only be applied inbound, in one direction.
00:13:02 - That's how they have the logic of the A 6 of the switch. So,
00:13:07 - I'm going to go into my switch and again, I'm not going to go
00:13:09 - through everything, because you just create an access list. It
00:13:12 - could be a standard one, it could be an extended access list,
00:13:15 - it could be a MAC address access list. You wander whatever interface
00:13:19 - you want and it's just like a router. If I want to apply an access
00:13:25 - list, how do you do it on a router? #ip access-group 1 in You
00:13:31 - can see inbound PACLs, so that doesn't give you the option for
00:13:35 - out. And it's saying "conflict with your vlan filters" that you've
00:13:38 - applied. So, it's giving me no worries, but that's now considered
00:13:44 - a PACL because it's applied there. Now if I wanted to apply a
00:13:46 - MAC address access list, I could just use #mac access-group
00:13:52 - and then you would type in the ACL name like I've created before
00:13:56 - and apply that inbound as well. Now you're filtering it based
00:13:59 - on the MAC address of the server. So, again, multiple ways that
00:14:04 - you can apply ACLs on layer 3 switches, VACLs to the entire landscape
00:14:08 - and PACLs to the port.
00:14:11 - I hate it when I do that. I summarized on a non-summary slide.
00:14:15 - So when I get to the summary slide, I think "Well, what do I
00:14:18 - say now?
00:14:20 - Look at that house. Isn't it neat?" I hope this has been informative
00:14:25 - to you and I'd like to thank you for viewing.

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Jeremy Cioara

Jeremy Cioara

CBT Nuggets Trainer

Certifications:
Cisco CCNA, CCDA, CCNA Security, CCNA Voice, CCNP, CCSP, CCVP, CCDP, CCIE R&S; Amazon Web Services CSA; Microsoft MCP, MCSE, Novell CNA, CNE; CompTIA A+, Network+, iNet+

Area Of Expertise:
Cisco network administration and development. Author or coauthor of numerous books, including: CCNA Voice 640-461 Official Cert Guide; CCNA Voice Official Exam Certification Guide (640-460 IIUC); CCENT Exam Prep (Exam 640-822); CCNA Exam Cram (Exam 640-802) 3rd Edition; and CCNA Voice 640-461 Official Cert Guide.


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