topic Re: V-lan Communication in Network Security

V-lan Communication

ray_stone — Mon, 11 Mar 2019 13:49:45 GMT

Hi, Currently we have two sites which are connected via STS IP Sec Tunnel and using Cisco ASA 5505. By default three zones are created:-

1) DMZ

2) Inside

3) Outside

Inside and DMZ are a part of V-lan 1 and outside is V-lan2. We have make exempted rule for communication between Inside and DMZ and added other remote local network also.

Now we have decided to make seperate V-lans for Inside and DMZ of eack site. Just want to know do we need any additional change in the configuration for communication among V-lans locally and remotely. Thanks

Re: V-lan Communication

andrew.prince — Fri, 26 Sep 2008 07:01:03 GMT

Ray,

No - as long as the VLAN's are sperate from each other - and the ASA has an interface in each of the VLAN's, you only need to allow traffic thru the ASA.

HTH>

Re: V-lan Communication

ray_stone — Fri, 26 Sep 2008 07:36:04 GMT

Would same exempted rule applicable for V-lan communication or it requires ip routing command like as a l3 switch configuration?

Re: V-lan Communication

andrew.prince — Fri, 26 Sep 2008 08:01:34 GMT

Ray - here is what I mean:-

Firewall Outside interface in a vlan with NO SVI Layer 3 interface on the switch

Firewall DMZ interface in a vlan with NO SVI Layer 3 interface on the switch

Firewall Inside interface in a vlan with SVI Layer 3 interface on the switch.

Then all other VLAN SVI's will communicate inter-vlan on the inside.

HTH>

Re: V-lan Communication

ray_stone — Fri, 26 Sep 2008 08:03:53 GMT

Sorry, I didn't understand properly. Request you to please mention in more details. Thanks

Re: V-lan Communication

andrew.prince — Fri, 26 Sep 2008 08:18:17 GMT

The outside vlan - does NOT have an ip address on the switch, it just passes traffic at layer 2.

The DMZ VLAN does not have an IP address on the switch, it just passes traffic at layer 2.

The Inside VLAN does have an IP address on the switch - the inside VLAN does pass traffic at layer 3 to the internal network.

HTH>

Re: V-lan Communication

Marwan ALshawi — Fri, 26 Sep 2008 11:37:49 GMT

hi Andrew

i think the routing between vlans from security prespective should be done through the firewall right ?

Ray

u have now inside in vlan and dmz in other vlan

if u make the intervlan routing on a switch then the comunication between dmz and inside will baypass the firewall not secure

however if u dont make SVIs as Andrew mentioned amd just make the switch pass L2 traffic to the firewall interface

and the firewall interface IP address should be the defual gateway for each host i the corsponding vlan

this way the firewall will handel the communication between VLANs

and take care of the requrment of NATing and ACL

good luck

if helpful Rate

Re: V-lan Communication

ray_stone — Fri, 26 Sep 2008 11:51:04 GMT

if u make the intervlan routing on a switch then the comunication between dmz and inside will baypass the firewall not secure :- Will the comunication secure between the V-lans through the FW. Thanks

Re: V-lan Communication

andrew.prince — Fri, 26 Sep 2008 11:53:17 GMT

Correct.

Re: V-lan Communication

andrew.prince — Fri, 26 Sep 2008 11:54:00 GMT

yep - correct

Re: V-lan Communication

ray_stone — Fri, 26 Sep 2008 12:08:15 GMT

May I know why its not secured while configuring on switch.

Another Query : If I configure three different V-lans like 100,200,300 on a L3 switch and add one interface for each V-lan and assign IP address which would be the gateway of client machines and switch is connected with FW and we are using STS Tunnel. Now I want the remote machines of other sites communicate with my all local V-lans. What wud be the process. Thanks

Re: V-lan Communication

andrew.prince — Fri, 26 Sep 2008 12:11:55 GMT

If you have layer 3 interfaces in those vlans, the IP traffic will bypass the firewall all together.

Re: V-lan Communication

ray_stone — Fri, 26 Sep 2008 12:23:31 GMT

Do we require to make sub interfaces on FW as it will bypass all network traffic for remote nodes. Please suggest?

Re: V-lan Communication

andrew.prince — Fri, 26 Sep 2008 12:25:05 GMT

Ray - this is off this topic.

What is it you are asking now?

Re: V-lan Communication

Marwan ALshawi — Fri, 26 Sep 2008 12:40:52 GMT

hi guys

ray

u can do it in diffrent ways first of all u need to know what u wana acieve

do u want the communication between vlans pass through the switch and the firewall do firewalling between ur internal networks and outside and remote site network

or u want the communication between vlans be firewalled and routed by the firewall as well

once u decide which method u wanna use then we can guid u easier

thank you

Re: V-lan Communication

Marwan ALshawi — Fri, 26 Sep 2008 12:41:48 GMT

this is 4 from me andrew 🙂

Re: V-lan Communication

andrew.prince — Fri, 26 Sep 2008 12:46:32 GMT

🐵

Re: V-lan Communication

ray_stone — Fri, 26 Sep 2008 13:21:36 GMT

Can you explain both scenario, if possible. Thanks

Re: V-lan Communication

andrew.prince — Fri, 26 Sep 2008 13:24:41 GMT

Ray,

The solution is born from the problem.

What are you trying to do/what do you want to do - if you do not know this, there is no solution - I hope this is plain enough.

Re: V-lan Communication

Marwan ALshawi — Sat, 27 Sep 2008 00:19:00 GMT

ok i will explain both 🙂

first one

lets say we have two internal vlans

vlan 10 10.1.1.0/24

vlan 20 20.1.1.0/24

and the scenario like

access_switch with two vlan 10,20---L3 switch---ASA--internet--

now lets consider the first way which is intervaln on the switch

i will creat third valn for the port connected from L3 switch and ASA called vlan 50

and the ASA ip is 50.1.1.1

now on the access switchs only make L2 vlans like

vlan 10

vlan 20

and the link between L2 switch and L3 switch is trunk

on L3 switch we need to creat L2 and L3 vlans

like:

vlan 10

interface vlan 10

ip address 10.1.1.1 255.255.255.0

no shut

vlan 20

interface vlan 20

ip address 20.1.1.1 255.255.255.0

no shut

vlan 50

interface vlan 50

ip address 50.1.1.2 255.255.255.0

no shut

now enable ip routing on L3 switch

ip routing

now make the port with ASA as acces port and put it in valn 50

now creat a defualt route point to ASA inside IP

ip route 0.0.0.0 0.0.0.0 5.1.1.1

if u do show ip route

u will see all VLANs interfaces as directly connected and defualt static route to the ASA

on ASA u need two route for internal networks through vlan50 interface

route inside 10.1.1.0 255.255.255.0 50.1.1.2

route inside 20.1.1.0 255.255.255.0 50.1.1.2

route outisde 0.0.0.0 0.0.0.0 interface [outisde interface]

nat (inside) 1 0 0

global (outisde) 1 interface

the defualt gateway for hosts in vlan 10 wil be 10.1.1.1

in vlan 20 will be 20.1.1.1

OR...:

dont make the VLAN interface on the L3 switch only L2 vlans and on the switch creat trunk port to the ASA and on ASA creat two subinterfaces each one in corsponding vlan like vlan 10 and vlan 20 and the same IP addressing

on the L3 switch

create make two access ports each one in a vlan that u have like one 10 and the other 20

and connect the access ports to diffrent physical por on ASA

now each vlan has its own interface or subinterface

both works and in both ways each ASA interface will have IP in this case this IP will be the defual gateway for the hosts in the corsponding vlan

thus the communication will be through ASA

u need only the route be done on the ASA

as we have done above each netwrok through the right interface and good luck u need ACLs as well from lower security to hgiher security interface communications

if helpful Rate