SonicWall Preempt Secondary Gateway

This is something fairly simple and obvious, but wanted to note it down anyways.

I wanted to use the SonicWall site-to-site VPN feature called “Preempt Secondary Gateway” found on the Advanced tab of VPN properties:

This is effectively VPN failback -if your primary goes down and then returns to service, the VPN will have been established on the secondary gateway and won’t renegotiate automatically back to the primary until the IKE lifetime expires. This can be a disadvantage in cases where the secondary gateway is a sub-par link or has metered bandwidth on it.

You will want to be careful with this setting however, if your primary has returned to service but isn’t stable – it could enable a renegotiation loop of your tunnel that would impact is availability.


I noticed on some VPNs this option was missing:


This is because a secondary gateway wasn’t specified; as soon as you define anything within that space (even the option dynamically appears on the Advanced tab.

Barracuda Tunnel to Sonicwall going down

A few months ago I solved a problem with a site-to-site VPN tunnel between a SonicWall NSA appliance and an Azure VM running Barracuda NextGen Firewall.

This VPN tunnel would go down once every 2-3 weeks, and only be restored if I manually re-initiated it from the Barracuda side.

I had intended on saving a draft of this post with details on the error I found in the Barracuda log, but apparently failed to do so.

So the short answer is make sure that “Enable Keepalives” is turned on, on the SonicWall side of the tunnel. This has brought stability to the VPN long-term.

Deploy VPN connection remotely

Here’s what I’ve developed to push a VPN client connection within Windows networking to remote PCs. One flaw is that this is user-based; I’m not sure if it could be applied to all users.

  1. Create a VPN connection with your desired settings on a template workstation
  2. Navigate to %appdata%\Microsoft\Network\Connections\Pbk
  3. Copy “rasphone.pbk” to a central source
  4. Either distribute that .pbk file directly to users to double-click on, or drop it into the same folder on their profile as it was originally retrieved from.

This .pbk file doesn’t store user credentials, so you will need to inform your user of those in advance.

Hyper-V NIC Team Networking issue

I encountered an issue with a Hyper-V virtual machine recently that had me very confused. I still don’t have a great resolution to it but at least a functional workaround.

At a site I have a Server 2012 R2 Hyper-V host (Host), a Server 2012 R2 file server guest (FileServer) and a Server 2012 R2 domain controller (DC).

The Host has two NICs in a single switch-independent address hash team. This Team is set as the source of the vSwitch which has management capabilities enabled. We wanted to use a NIC team to provide network redundancy in case a cable was disconnected as this network is being provided by the site owner rather than my company.

Host and FileServer could reach DC, but nothing else could. DC could reach Host and FileServer, but not even it’s own default gateway.

This immediately sounded like a mis-configured virtual switch on Host, as it appeared DC could only access internal traffic. But I confirmed the vswitch was set to “External” and if this were the case the FileServer would have presumably been affected by this issue as well, but it was not.

I tried disabling VMQ on the Host NICs, as well as Large Send Offload, since both those features have been known to cause problems, but that did not resolve the issue either.

I tried changing the teaming algorithm to Hyper-V Port and Dynamic, but that didn’t resolve the issue either.

Then I decided to put one of the NICs into a Standby state in the team. This caused the accessibility to switch between the VMs; all of a sudden nothing external could reach my file server, but the DC came online to external traffic.

I tried changing which NIC was in standby but that still left me with one VM that had no connectivity.

My assumption at this point is that this issue is being caused by Port Security on the network switches; something that we are aware the site owner is doing. I suppose that the Team presents a single MAC address across multiple ports, which the port security doesn’t like and so it blocks traffic from one side of that team. Because of how traffic is balanced across the team it leaves one of the VMs in an inaccessible state.

Unfortunately we do not have control over this network or the ability to implement LACP, and so I’ve had to remove the NIC teaming and go back to segregated NICs for management and VM access.


File Server and remote office collaboration

I had someone email me about DFSR and file locking based on some old comments on a Ned Pyle post from the Ask DS blog on technet.
I wrote up a detailed response of how I’ve handled this issue in my environment, and decided that response would make a good post to share, so here it is:


It’s a long story actually. Not sure if you read my post from April 2013, but I effectively gave up on DFSR due to the instability we were experiencing. Still not sure if it was underlying storage causing it, or just the scale at which we were operating. PeerSync couldn’t keep up with the rate of change on our file servers when we piloted it, and neither could PeerLock when we tried to integrate it with DFSR.

So stuff crashed in April 2013, I gave up on DFSR and we intended on using Silver Peak WAN acceleration across our site-to-site VPNs, combined with RDS or Citrix XenApp.

Then my company was acquired by a much bigger engineering firm, and all my plans were interrupted. We basically left our users to suffer (since we had already used DFSR to create a single namespace, when we quit DFSR we just kept a ‘single source of truth’) for months because the parent company was going to roll out a global WAN.

That did eventually happen in late 2014, so at that point we had Riverbed Steelheads providing 80% data reduction across the WAN and a 7ms link between our biggest branch and head office (where the most pain was for ACAD production).

We occasionally heard rumbling from staff that it wasn’t good enough, and so we pressed on-wards with purchase of a 30-seat Citrix XenApp environment with a dedicated nVidia GRID K2 card for GPU acceleration. However we really screwed up the user communication and training and failed to get adequate buy-in from CAD management to enforce it’s use.

XenApp works fantastic for apps like ArcGIS Desktop and GlobalMapper, but

we really struggled with mouse lag in all AutoCAD streams (except Revit which we don’t use). We went as far as a specialized consultant out of the UK and they couldn’t figure it out either.

I had begun the process of looking at Panzura, which I raved about here. It still looks like the best overall solution to a centralized file server with geographic collaboration on AutoCAD files. But the price tag for two offices was close to $60k not counting cloud storage costs, and I had just purchased a whole bunch of new storage so i didn’t want new Panzura hardware, and they don’t support Hyper-V for their virtual instance (which still blows my mind).

Ultimately, a couple months ago we had a big meeting with all our CAD managers and consensus was that:
– The majority of work performed in branch offices is acceptable due to the Riverbed Steelheads and low latency provided by the global WAN
– The work that doesn’t perform well due to huge file sizes would be done with XenApp and the mouse lag would just be accepted. But I don’t think the CAD managers are actively encouraging this.

And that’s where we’re at right now; not really solving the issue but trying to find improvements as best we can.