ASA Pro Tip — A Better Prompt

The Cisco ASA FW has a simple and robust failover mechanism. It works so well that sometimes an administrator may not realize that the load has moved from the primary device to the secondary device. When connecting to the IP address, the primary IP address for the interface follows the active unit. So it is even possible to be logged in to a different Firewall than the administrator thinks they are in.

This can easily be determined by doing a show failover.  In the output, it is easy to see if the unit is the Primary or Secondary (configured state) and Active or Standby (operational state). Since the ASA Failover is not preemptive, any glitch moving the load to standby will result in the load remaining there (unless there is a subsequent failure or manual failback).

Given the fact that I am a huge fan of situational awareness, I like to reflect the state in the CLI prompt. This is a simple configuration change.

asav-1# conf t
asav-1(config)# prompt hostname priority state 
asav-1/pri/act(config)# exit

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ASA Active/Standby with BDI/BVI

I see a lot of ASA designs and they are typically flanked with switches. One of the reasons for this is that the failover requirements typically dictate that the devices to be layer 2 adjacent in each security zone. There is obviously the requirement to be L3 directly connected to their next hop. The result of this requirement that an ASA can’t typically be directly connected directly to an L3 only device and it is often the case that a switch is sandwiched between the FW and the next L3 device.

This article is meant to outline a possible work around with IOS and IOS-XE based routers to provide the L2 two adjacency using inherit L2 features. Readers may use these sample configurations to build out there own labs and more fully validate the applicability the their environment. Continue reading

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Quickly Adding an NMS to VIRL

I’ve spent the last few days experimenting with APIC-EM and the path trace capabilities. My lab environment is currently leveraging VIRL (Virtual Internet Routing LAB). Since it wasn’t obvious how to integrate APIC-EM with the lab platform, I wanted to share my configuration.

TL;DR–When building the topology, click the background and view the properties for the Topology. Change the Management Network to “Shared flat network”. This will put the all of the devices ‘Mgmt-intf’ vrf on the ‘flat’ ( by default) network when the topology is built. 

When I started this process, I really didn’t realize how easy it could be. I actually tried to leverage a manual connection to L2 External (FLAT) to do the management in-band for the topology. This is certainly possible, but there is a much easier way. As most VIRL users have noticed, there is a management IP address that gets assigned to each device. There is a simple configuration change that will allow that address to be one from the ‘FLAT’ pool and connected externally to the ‘L2 External (FLAT)’ network.


My configuration 

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A Broken Process Placing Consumers at Risk

Below is a chat session I had with Pearson Vue several months ago as I attempted to schedule a recertification exam. Apparently, I have two accounts with them and that prevents next day test scheduling. To put it mildly, I don’t think they adequately explain how they could possibly guarantee non-disclosure of data with email as a transport. Moreover, this seems to indicate a serious disconnect between security and business operations.

Screen Shot 2016-04-07 at 2.00.18 PM

Image Link – for FULL Size View

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APIC-EM Path Trace Examples – Overlay Networks

Since seeing the APIC-EM Path Trace demo for the first time and seeing how it represents CAPWAP, I’ve been curious how well it deals with other types of overlay/underlay networking. This article is a brief synopsis of that testing and provides some visuals around what was produced with this free management tool.

TL;DR–APIC-EM adds value to most network path traces and typically represents what it knows. The single exception is with MPLS VPNv4. If the MPLS PE nodes are pulled into the device inventory, path trace has a total lack of understanding around the recursive lookup into the global vrf that is required for VPNv4 functionality.

CAPWAP Representation — The Gold Standard

I wanted to start out by showing what an ideal representation of an overlay network would be for a tool like this. Path Trace understands AND clearly represents both the underlay and the overlay network for traffic flowing through a CAPWAP tunnel. The image below shows the extent of the tunnel (darker gray) and the physical components that are responsible for delivery (both through the tunnel and outside of the tunnel).


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Voice Gateway and Voice VRF – Caveats

Many networks leverage what is known as a VRF. These are used for traffic isolation and create separate routing instances within a router. It is important that vrf awareness is confirmed for any service (DHCP, Voice GW, etc) being locally provided for a given point in the network. One use case for such a configuration might be for voice isolation with or without MPLS. In the case that a router is providing voice gateway functionality (i.e. FXO/FXS to VOIP), the voice functions must understand the VRF construct in order to properly fulfill the role.

TL;DR–This configuration sometimes does not behave as expected and, in my experience, may require a reboot after following the documented procedure.

The configuration for VRF-Aware H.323 and SIP for Voice Gateways can be found at the URL below.

Notice that it makes reference to the fact that the services need to be restarted–

To configure a voice VRF, you must shut down voice services on the gateway, assign a previously defined VPN VRF to the VoIP SPI, and then restart voice services.

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ACL Trace in APIC EM

I wanted to take just a moment to share the output of an APIC-EM ACL Trace (option in Path Trace). For this example, I have built out the topology below.


The applicable configuration for CSR1000v-2 is as follows– Continue reading

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FLAT Networks in VIRL Require Promiscuous Mode

So I’m sure this is in the documentation somewhere. But for anyone else out there who is getting inconsistent results with FLAT interfaces in VIRL, Promiscuous Mode support in ESXi seems to be a requirement. Definitely something to check…


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Connecting VIRL to the Outside World

I’ve been leveraging VIRL for some time to build and test self-contained labs. I’ve always known that there was some ability to connect to the world outside of this environment. Recently, I decided to configure this functionality and I wanted to take just a moment to share what I found.

First and foremost, this isn’t anything difficult or time consuming. So if you have a need to leverage physical devices with your VIRL deployment, don’t hesitate before building it out.

There are two mechanisms for outside connectivity. The first mechanism is called SNAT. This method basically builds static NAT in and out of the environment. I get how this could be beneficial, but I would typically prefer to keep any NAT configuration contained to an environment that I am very familiar with (possibly an ASA or IOS instance outside the lab when an additional NAT layer is required).

The second method, and configuration we will be testing is called FLAT. In this configuration, VIRL connects a L2 broadcast domain between a lab device and an Ethernet interface. In my example I am running the VIRL components in a VM environment on ESXi. So this is a virtual interface that needs to be mapped through the VMWare vSwitch.

To test this functionality, I created the following topology.


From a VIRL perspective, there are a couple of things to be aware of. The default configuration would have VIRL owning the subnet and the external default GW existing at Continue reading

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Hairpinning traffic through ASA with State Bypass

Several years ago I wrote an article about the Woes of Using an ASA as a Default Gateway. I have received a lot of feedback about this post and recently had a request for an update around ASA > 8.3. When building this scenario out with current ASA code, I found that the base NAT configuration (internet only PAT) had no bearing on the hairpin configuration. As expected, I found the same challenge around state bypass. I wanted to share a current post that demonstrates the challenges and solutions when traffic is bounced off the inside interface of the ASA.

ASA Hairping

The requirements of the configuration are as follows–

  • TestHost must be able to Telnet and Ping to Internet and PartnerHost
  • The inside interface of asav-1 must be the default gateway for TestHost
  • asav-1 is doing PAT for Internet destined traffic
  • PartnerRTR and ParnterHost have been preconfigured as shown above

The following are the base configurations for all of the devices. The configuration of asav-1 does not seem to allow communication from TestHost to PartnerHost ( network). Continue reading

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Creating a Firepower Peer to Peer Dashboard

Peer to peer applications are a significant challenge for policy enforcement solutions. Any flows that slip through as an undetermined application type may allow the file sharing app to function. The first key to addressing this challenge is simple visibility into which hosts or users may be abusing the AUP with these types of applications. This article shows a quick and easy way to create Peer to Peer dashboard in the Firepower Management Console.

For those that have already attempted this, there are a number of challenges that may have surfaced. First there are no readily available widgets or criteria that will show the desired information. Experimenting with search constraints and the connection table quickly reveals that the desired information can be easily accessed by using the “peer to peer” Application Protocol Category search criteria. Unfortunately, the Connection Table is not readily available to the Dashboard Widgets. The Connection Summary table is available, but it does not have the Application Protocol Category (required for the search constraints).

My goal was to build a few dashboard widgets to give visibility into Peer to Peer activity. For this article I will demonstrate the steps required to build those widgets. The first widget will provide a list of Peer to Peer applications on the network, the second will provide a list of initiating IP addresses of peer to peer connections, and the third widget will sort actions taken on peer to peer traffic. All of these will be sorted based on the connection count.

CustomTablesTo overcome the challenge of not having access to the Connection Table from the Dashboard Widgets, it is necessary to create a custom table. To do so, choose Analysis, Custom > Tables, Custom Tables. 

The next step is to create a new Custom Table by choosing Create Custom Table. This allows for logical table joins between tables that contain combinable data. For this example, there is really only a need for a handful of fields from Connection Events. However, it is necessary to add at least one field from another table to allow the custom table creation. I have added the following fields from Connection Events: PeerToPeerTableApplication Protocol, Application Protocol Category, Initiator IP, and Action. I have also added IP Address from the Hosts table so it contains fields from multiple tables. This isn’t really necessary, but the UI doesn’t allow it to be saved otherwise. Continue reading

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Firepower Access Control Policies

The Firepower ecosystem is a powerful NGIPS/NGFW solution. At that heart of the configuration construct is what is known as the Access Control Policy. Comparing this to something familiar is possible by thinking about the much simpler filtering feature in the ASA. For comparison, an ASA’s access-list (ACL) has multiple access-control entries (ACE’s). Each of these entries can refer to object-groups, networks, and protocols and can apply a permit or deny action.

The Access Control Policy in Firepower is a similar concept, but there are many additional facets that are pulled together to provide a more comprehensive policy application mechanism. This article only covers the major areas of this policy control construct. There are items which are beyond the scope including variable sets and manipulating the behavior of http response pages.

Specific to the policy application, there are two main areas of the the Access Control Policy. The first area is what is known as Security Intelligence. In the policy, this is found on the second tab from the left and provides a framework for blacklisting. There are many feeds provided directly from Cisco’s Talos organization and are ready for consumption by the security policy.

The action for each feed that is blacklisted can be set to monitor only or to block. These events will be logged as Security Intelligence Events and may raise an Indication of Compromise. It is also this tab that will allow for the selection of a DNS Policy. Worth noting is that whitelisting is an override for blacklisting. Whitelisting does not preclude processing against the remaining Firepower Access Control Rules.

The second, and most visible, component contains the Access Control Rules. This is located in the left-most tab of the Access Control Policy. The section is a familiar construct in which rules are processed in a top-down manner until a match occurs. In the case that the action is Monitor, further processing occurs. If the action is Trust, Allow or Block, rule processing terminates and the appliance will process the traffic accordingly. A Trust action indicates that the traffic should be fully trusted and not subject to IPS checks (against the Snort signatures). Allowed traffic may be sent to IPS for additional processing.

Access Control Rule

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