topic Re: Adding third firewall in Network Security

Adding third firewall

gcook0001 — Thu, 16 Feb 2023 17:54:03 GMT

I am in the process of adding a third firewall to our network. We have two FTD 1140 in HA mode in the data center. The new firewall is a FTDv but will be replaced with a 1120 when it becomes available. Currently our office is connected to our data center using a VPLS. This is not going to change but the goal is to provide internet access directly from the office. The issue that I am running into is inter-vlan routing. Before adding the third firewall it wasn't a problem. Traffic between vlans would traverse the firewall and we use ACLs to control access. Now with the new firewall if I set the default gateway to be the FTDv I can access anything on the same vlan but I can't cross vlans. I know this is a routing issue and I am wondering what the best way to handle this would be.

Re: Adding third firewall

Rob Ingram — Thu, 16 Feb 2023 19:12:35 GMT

@gcook0001 can you provide a diagram, as your topology is not clear.

Is routing setup correctly on connected devices to route through the FTD?

And does the FTD have all the correct routes?

Do you have Access Control rules to permit the traffic?

Do you have NAT setup, which could unintentially translate traffic?

Can you run packet-tracer from the CLI to simulate the traffic flow and provide the output for review.

Re: Adding third firewall

gcook0001 — Thu, 16 Feb 2023 20:30:00 GMT

Thanks for the reply. Here is what I am looking at

The goal is to have the PC access the internet via Firepower-3, the server via Firepower-1. I need to have the PC be

able to reach the server, and vice versa. I was partially able to do this by adding a second gateway to my test pc so that it has both AAA.AAA.3.3 and AAA.AAA.3.1. Not sure if this is the best way to this. We do want the traffic traversing the firewalls when crossing vlans as we want to inspect the traffic.

I have the static routes setup
Firepower-1 - NAT Rules after

Firepower-3 - Nat Rules after

> packet-tracer input OFFICE-SSMIC icmp 172.29.3.100 0 0 172.30.0.30

Phase: 1
Type: ACCESS-LIST
Subtype:
Result: ALLOW
Elapsed time: 8400 ns
Config:
Implicit Rule
Additional Information:
MAC Access list

Phase: 2
Type: ROUTE-LOOKUP
Subtype: No ECMP load balancing
Result: ALLOW
Elapsed time: 21900 ns
Config:
Additional Information:
Destination is locally connected. No ECMP load balancing.
Found next-hop 172.30.0.30 using egress ifc OFFICE-MGMT(vrfid:0)

Phase: 3
Type: ACCESS-LIST
Subtype: log
Result: ALLOW
Elapsed time: 7050 ns
Config:
access-group CSM_FW_ACL_ global
access-list CSM_FW_ACL_ advanced permit ip any any rule-id 268459009
access-list CSM_FW_ACL_ remark rule-id 268459009: ACCESS POLICY: Office-Policy - Mandatory
access-list CSM_FW_ACL_ remark rule-id 268459009: L7 RULE: test
Additional Information:
This packet will be sent to snort for additional processing where a verdict will be reached

Phase: 4
Type: CONN-SETTINGS
Subtype:
Result: ALLOW
Elapsed time: 7050 ns
Config:
class-map class-default
match any
policy-map global_policy
class class-default
set connection advanced-options UM_STATIC_TCP_MAP
service-policy global_policy global
Additional Information:

Phase: 5
Type: NAT
Subtype: per-session
Result: ALLOW
Elapsed time: 7050 ns
Config:
Additional Information:

Phase: 6
Type: IP-OPTIONS
Subtype:
Result: ALLOW
Elapsed time: 7050 ns
Config:
Additional Information:

Phase: 7
Type: INSPECT
Subtype: np-inspect
Result: ALLOW
Elapsed time: 46500 ns
Config:
class-map inspection_default
match default-inspection-traffic
policy-map global_policy
class inspection_default
inspect icmp
service-policy global_policy global
Additional Information:

Phase: 8
Type: INSPECT
Subtype: np-inspect
Result: ALLOW
Elapsed time: 4200 ns
Config:
Additional Information:

Phase: 9
Type: QOS
Subtype:
Result: ALLOW
Elapsed time: 0 ns
Config:
Additional Information:

Phase: 10
Type: FLOW-CREATION
Subtype:
Result: ALLOW
Elapsed time: 9900 ns
Config:
Additional Information:
New flow created with id 17553, packet dispatched to next module

Phase: 11
Type: EXTERNAL-INSPECT
Subtype:
Result: ALLOW
Elapsed time: 16800 ns
Config:
Additional Information:
Application: 'SNORT Inspect'

Phase: 12
Type: SNORT
Subtype: appid
Result: ALLOW
Elapsed time: 39014 ns
Config:
Additional Information:
service: ICMP(3501), client: (0), payload: (0), misc: (0)

Phase: 13
Type: SNORT
Subtype: firewall
Result: ALLOW
Elapsed time: 3662104 ns
Config:
Network 0, Inspection 0, Detection 0, Rule ID 268459009
Additional Information:
Starting rule matching, zone 4 -> 20, geo 0 -> 0, vlan 0, src sgt: 0, src sgt type: unknown, dst sgt: 0, dst sgt type: unknown, user 9999997, no url or host, no xff
Matched rule ids 268459009 - Allow

Result:
input-interface: OFFICE-SSMIC(vrfid:0)
input-status: up
input-line-status: up
output-interface: OFFICE-MGMT(vrfid:0)
output-status: up
output-line-status: up
Action: drop
Time Taken: 3837018 ns
Drop-reason: (inspect-icmp-seq-num-not-matched) ICMP Inspect seq num not matched, Drop-location: frame 0x0000556c7084ee08 flow (NA)/NA

Re: Adding third firewall

Rob Ingram — Thu, 16 Feb 2023 20:36:23 GMT

@gcook0001 you could plug the VPLS directly into Firepower 3 on another dedicated internet.

Create sub-interfaces for each of the VLANs, use the Firepower SVI IP for the VLAN as the default gateway for the PCs on those VLANs. That way all traffic between VLANs is routed to the firewall and subsequently routed to another VLAN (if ACP) permits, the Internet or access the servers.

Re: Adding third firewall

gcook0001 — Thu, 16 Feb 2023 21:02:11 GMT

I just thought of something. In the given diagram when the PC pings the Server since they are on different vlans the traffic goes to firepower-3, then it tries to send the traffic back to the switch. I believe this would have the same affect as a hairpin vpn connection.

So if connect the VPLS to the firewall instead it would eliminate that issue. I may have to do it at both ends for the same reason.

Please correct me if I am wrong on this.

Re: Adding third firewall

Rob Ingram — Thu, 16 Feb 2023 21:15:22 GMT

@gcook0001 yes, it sounds like that what you've configured - traffic from the PC is sent up to Firepower3 (as it's the default gateway) then back down to the switch. I imagine the return traffic does not traverse Firepower3

So use the suggestion above, route the traffic in the different VLANs and the VPLS connection between separate FTD interfaces (physical or sub-interfaces), with FTD doing the routing between the VLANs and over the VPLS. Return traffic would have to take the same path.

Re: Adding third firewall

gcook0001 — Wed, 22 Feb 2023 18:30:07 GMT

Yeah. Unfortunately that was not the issue. Still trying to figure this out.

Re: Adding third firewall

gcook0001 — Mon, 06 Mar 2023 21:18:31 GMT

I found the following information on setting up NAT for multiple devices. What I am trying to figure out is how does a device on the internal network select which firewall to use.

Customizing NAT Rules for Multiple Devices

Because the NAT policy is shared, you can assign a given policy to more than one device. However, you can configure at most one auto NAT rule for a given object. Thus, if you want to configure different translations for an object based on the specific device doing the translation, you need to carefully configure the interface objects (security zones or interface groups) and define network object overrides for the translated address.

The interface objects determine on which devices a rule gets configured. The network object overrides determine what IP addresses are used by a given device for that object.

Consider the following scenario:

FTD-A and FTD-B have inside networks 192.168.1.0/24 attached to the interface named “inside.”
On FTD-A, you want to translate all 192.168.1.0/24 addresses to a NAT pool in the 10.100.10.10 - 10.100.10.200 range when going to the “outside” interface.
On FTD-B, you want to translate all 192.168.1.0/24 addresses to a NAT pool in the 10.200.10.10 - 10.200.10.200 range when going to the “outside” interface.

To accomplish the above, you would do the following. Although this example rule is for dynamic auto NAT, you can generalize the technique for any type of NAT rule.

Procedure

Step 1

Create the security zones for the inside and outside interfaces.

Choose Objects > Object Management.
Select Interface Objects from the table of contents and click Add > Security Zone. (You can use interface groups instead of zones.)
Configure the inside zone properties.
- Name—Enter a name, for example, inside-zone.
- Type—Select Routed for routed-mode devices, Switched for transparent mode.
- Selected Interfaces—Add the FTD-A/inside and FTD-B/inside interfaces to the selected list.
Click Save.
Click Add > Security Zone and define the outside zone properties.
- Name—Enter a name, for example, outside-zone.
- Interface Type—Select Routed for routed-mode devices, Switched for transparent mode.
- Selected Interfaces—Add the FTD-A/outside and FTD-B/outside interfaces to the selected list.
Click Save.

Step 2

Create the network object for the original inside network on the Object Management page.

Select Network from the table of contents and click Add Network > Add Object.
Configure the inside network properties.
- Name—Enter a name, for example, inside-network.
- Network—Enter the network address, for example, 192.168.1.0/24.
Click Save.

Step 3

Create the network object for the translated NAT pool and define overrides.

Click Add Network > Add Object.
Configure the NAT pool properties for FTD-A.
- Name—Enter a name, for example, NAT-pool.
- Network—Enter the range of addresses to include in the pool for FTD-A, for example, 10.100.10.10-10.100.10.200.
Select Allow Overrides.
Click the Overrides heading to open the list of object overrides.
Click Add to open the Add Object Override dialog box.
Select FTD-B and Add it to the Selected Devices list.
Click Override and change Network to 10.200.10.10-10.200.10.200
Click Add to add the override to the device.
By defining an override for FTD-B, whenever the system configures this object on FTD-B, it will use the override value instead of the value defined in the original object.
Click Save.

Step 4

Configure the NAT rule.

Select Devices > NAT and create or edit an FTD NAT policy.
Click Add Rule.
Configure the following properties:
- NAT Rule = Auto NAT Rule.
- Type = Dynamic.

On Interface Objects, configure the following:

Source Interface Objects = inside-zone.
Destination Interface Objects = outside-zone.

Note

The interface objects control on which devices the rule is configured. Because in this example the zones contain interfaces for FTD-A and FTD-B only, even if the NAT policy were assigned to additional devices, the rule would be deployed to those 2 devices only.

On Translation, configure the following:
- Original Source = inside-network object.
- Translated Source > Address= NAT-pool object.
Click Save.
You now have a single rule that will be interpreted differently for FTD-A and FTD-B, providing unique translations for the inside networks protected by each firewall.

Re: Adding third firewall

gcook0001 — Thu, 09 Mar 2023 20:58:28 GMT

So I was finally able to find a solution that works. I had two issues. The first is in ESXI the port groups need to have the VLAN set to 0.

The second thing is in the FMC when creating the interfaces for the third firewall since the subnets span all the firewalls you need to use the same security zones on all the firewalls. I was using a seperate security zone on the third firewall since if I made a change it would ask me to deploy the change to all the firewalls. I wasn't sure if that would cause an issue - it doesn't.