You can configure many firewalls to act as a router (layer-3 firewall) or as a
switch bridge (layer-2 firewall). The oft-ignored detail: how does a layer-2 firewall handle ARP (or any layer-2 protocol)?
Unless you want to use static ARP tables it’s pretty obvious that a layer-2 firewall MUST propagate ARP. It would be ideal if the firewall would also enforce layer-2 security (ARP/DHCP inspection and IPv6 RA guard), but it looks like at least PAN-OS version 11.0 disagrees with that sentiment.
Straight from Layer 2 and Layer 3 Packets over a Virtual Wire:
I have blog post ideas sitting in my to-write queue for over a decade. One of them is why would you need a VRF (and associated router) between virtual servers and a firewall?
Andrea Dainese answered at least part of that question in his Off-Path firewall with Traffic Engineering blog post. Enjoy!
Initial implementation of Noël Boulene’s automated provisioning of NSX-T distributed firewall rules changed NSX-T firewall configuration based on Terraform configuration files. To make the deployment fully automated he went a step further and added a full-blown CI/CD pipeline using GitHub Actions and Terraform Cloud.
Not everyone is as lucky as Noël – developers in his organization already use GitHub and Terraform Cloud, making his choices totally frictionless.
Noël Boulene decided to automate provisioning of NSX-T distributed firewall rules as part of his Building Network Automation Solutions hands-on work.
What makes his solution even more interesting is the choice of automation tool: instead of using the universal automation hammer (aka Ansible) he used Terraform, a much better choice if you want to automate service provisioning, and you happen to be using vendors that invested time into writing Terraform provisioners.
A couple of months ago I had the pleasure to publish my first guest post here and, as to be expected from ipspace.net, it triggered some great discussion.
With this input and some open thoughts from the last post, I want to dive into a few more topics.
Before we start: if you’re new to my blog (or stumbled upon this blog post by incident) you might want to read the Considerations for Host-Based Firewalls for a brief overview of the challenge, and my explanation why flow-tracking tools cannot be used to auto-generate firewall policies.
As expected, the “you cannot do it” post on LinkedIn generated numerous comments, ranging from good ideas to borderline ridiculous attempts to fix a problem that has been proven to be unfixable (see also: perpetual motion).
I have NEVER found a customer application team that can tell me all the servers they are using, their IP addresses, let alone the ports they use.
His proposed solution: use software like Tetration (or any other flow collecting tool) to figure out what’s really going on:
Perhaps a paradigm shift is due for firewalls in general? I’m thinking quickly here but wondering if we perhaps just had a protocol by which a host could request upstream firewall(s) to open access inbound on their behalf dynamically, the hosts themselves would then automatically inform the security device what ports they need/want opened upstream.
Having spent my career in various roles in IT security, Ivan and I always bounced thoughts on the overlap between networking and security (and, more recently, Cloud/Container) around. One of the hot challenges on that boundary that regularly comes up in network/security discussions is the topic of this blog post: microsegmentation and host-based firewalls (HBFs).
Two weeks ago Nicola Modena explained how to design BGP routing to implement resilient high-availability network services architecture. The next step to tackle was obvious: how do you fine-tune convergence times, and how does BGP convergence compare to the more traditional FHRP-based design.
Remember the “BGP as High Availability Protocol” article Nicola Modena wrote a few months ago? He finally found time to extend it with BGP design considerations and a description of a seamless-and-safe firewall software upgrade procedure.
After publishing the Disaster Recovery Faking, Take Two blog post (you might want to read that one before proceeding) I was severely reprimanded by several people with ties to virtualization vendors for blaming virtualization consultants when it was obvious the firewall clusters stretched across two data centers caused the total data center meltdown.
Let’s chase that elephant out of the room first. When you drive too fast on an icy road and crash into a tree who do you blame?
- The person who told you it’s perfectly OK to do so;
- The tire manufacturer who advertised how safe their tires were?
- The tires for failing to ignore the laws of physics;
- Yourself for listening to bad advice
For whatever reason some people love to blame the tires ;)
In last week’s continuation of EVPN never-ending story Lukas Krattiger described how you could use EVPN constructs (VNIs, VRFs) to implement service insertion, and how you could combine then with policy-based routing.
TL&DW: It’s bridging and routing ;)
You’ll need Standard ipSpace Subscription to access the videos.
I spent a lot of time during this summer figuring out the details of NSX-T, resulting in significantly updated and expanded VMware NSX Technical Deep Dive material… but before going into those details let’s do a brief walk down the memory lane ;)
You might remember a startup called Nicira that was acquired by VMware in mid-2012… supposedly resulting in the ever-continuing spat between Cisco and VMware (and maybe even triggering the creation of Cisco ACI).
This is a guest blog post by Andrea Dainese, senior network and security architect, and author of UNetLab (now EVE-NG) and Route Reflector Labs. These days you’ll find him busy automating Cisco ACI deployments.
Following the Ivan’s post about Firewall Ruleset Automation, I decided to take a step forward: can we always have up-to-date and clean firewall policies without stale rules?
We usually configure and manage firewalls using a process like this: