Cisco’s Virtual CUBE & Modern IOS Toll Fraud Security

Good Morning Web World!

I found myself with a little bit of time this morning and I thought I’d share a bit of my latest tinkering.

Those of you that have followed this blog for a while may remember my first post where I talked about pointing a CUBE through an ASA out to my ITSP, Flowroute. That post is located here for your reading pleasure.

While the software/hardware has changed with my setup the idea is basically the same. I still have a CUCM system (now 11.x) running with a phone (I’ve felt like being different lately so currently I’m using a retro 7985G as my endpoint (G in this case does not mean Gigabit)). I also have a firewall, a Cisco 5506-X (it was time for an upgrade from the 5505) and I do still have a CUBE. My previous CUBE was a 3825 and it worked wonderfully but the 3825 has long since outlived its relevance in today’s enterprise environments. In my stack of possibilities I also have a 2921 and while it is still a very powerful and valid router, it just seems too easy.

Simple and straight forward is great but only until you’ve done simple and straight forward, then it becomes time to mix it up.

To that end, my replacement CUBE is virtual. Yes, I said virtual. If you follow Cisco and their products, you may already know about the Cloud Services Router, the CSR1000V. The CSR1000V is a virtual router that runs on a VMWare ESXi host. It runs IOS XE though there is some Linux/Unix on the backend that makes it tick.


Virtual CUBE Show Commands



When I first heard that it was possible to turn a CSR1000V into a CUBE, I was skeptical. As I have worked through the configurations and witnessed it work, I must say I am impressed.  The configuration is the same as with any other IOS XE router with exception of the interface naming conventions. There are three (3) Gigabit Ethernet interfaces and they are named Gigabit Ethernet 1, Gigabit Ethernet 2 and Gigabit Ethernet 3.  The configuration in ESXi is shown below.

CSR1000V Interfaces Config

In my case, I created three (3) separate interfaces on my vSwitch and pointed them at three (3) separate VLANs in my infrastructure. You could bond/Port Channel these interfaces if you wanted too but you will still be limited by the throughput of your host’s uplink(s).

A few important things to note…

  • When you deploy the OVA file in ESXi you are given a choice of multiple router “sizes” i.e. memory and processor. I am using the smallest size which is one vCPU and 4GB of vRAM. Some of the larger installations require an additional license.
  • Keep in mind that I am testing this configuration in a controlled lab environment. I am not sure of scale-ability and if you read Cisco’s CUBE configuration guide, located here, you’ll see that the virtual CUBE does have several restrictions that may make it impractical for some organizations.
  • In my previous post, my 3825 CUBE was running 12.4 IOS which did not include Toll Fraud Prevention, starting in 15.x and moving through IOS XE you need to be mindful of TFP and what it means when you are trying to make/receive calls on a Cisco H.323 or SIP Gateway.

Let’s talk for a moment on Toll Fraud Prevention. As stated above, all modern IOS and IOS XE versions include Toll Fraud Prevention mechanisms and if you use a router, physical or virtual, for voice you need to be aware of them.

Voice Service Config



If you look at the configuration snippet above, you’ll see that in the voice service configuration there is a trusted IP Address list. That list contains the IPs of my ITSP and my CUCM. If I remove those IPs from the list, calls fail. If you are linking your CUBE or gateway to multiple CUCMs or other systems you’ll want to have those IPs in that list as well. What this list does is let the good/known IPs in to complete transactions/calls on the gateway/CUBE and keeps the unknown/bad IPs out to prevent them from placing calls on the system. If you’ve ever set up an IP PBX on internet, you know that Toll Fraud is a real and serious threat. If you don’t want or need this feature you can also turn it off by entering “no ip address trusted authenticate” in your voice service configuration. This is not a recommended configuration but in your environment the TFP mechanisms may do more harm than good.

Thanks for reading, I hope this has been informative.


When Good VTP Goes Bad

Just a quickie tonight folks…

I am expanding my network and relocating my servers and other “noisy” hardware to my basement. The cooling value of the dry subterranean environment is great but in all honesty I’m trying to keep my better half happy and my office is not a great place for network gear and servers apparently.

With this relocation I am expanding my switching infrastructure from my core 3560G to include a 2960G as well. The addition of this switch gives me the opportunity to play with VTP or the VLAN Trunking Protocol.

VTP is a Layer 2 protocol that allows you to configure all of your VLANs on the “server” and then feed them down to the “clients”. VTP is a proprietary Cisco protocol and for large, diverse networks it may not be the best option but for me it works, at least it was supposed to.

I say supposed to, because I configured it, using version 2 and nothing happened. Below are my configurations…

CORE-3560G-01(config-vlan)#do show vtp status
VTP Version capable             : 1 to 3
VTP version running             : 2
VTP Domain Name                 : SPRNET
VTP Pruning Mode                : Disabled
VTP Traps Generation            : Disabled
Device ID                       : 000a.b8d3.0400
Configuration last modified by at 8-22-16 01:52:57
Local updater ID is on interface Vl1 (lowest numbered VLAN interface found)
Preferred interface name is gig0/49

Feature VLAN:
VTP Operating Mode                : Server
Maximum VLANs supported locally   : 1005
Number of existing VLANs          : 23
Configuration Revision            : 0
MD5 digest                        : 0x85 0x94 0x36 0x46 0xC1 0xCE 0xE0 0xD0          
                                    0x87 0x0A 0xF2 0xD4 0x24 0xD0 0xF8 0xD2
BASEMENT-2960G-01#show vtp sta
VTP Version capable             : 1 to 3
VTP version running             : 2
VTP Domain Name                 : SPRNET
VTP Pruning Mode                : Disabled
VTP Traps Generation            : Disabled
Device ID                       : 0017.594c.b180
Configuration last modified by at 3-15-93 06:29:46

Feature VLAN:
VTP Operating Mode                : Client
Maximum VLANs supported locally   : 255
Number of existing VLANs          : 5
Configuration Revision            : 0
MD5 digest                        : 0x7D 0x73 0xB1 0x19 0x35 0xDC 0xE2 0xA8
                                    0x3A 0x07 0xE0 0xBF 0x92 0xFA 0x53 0x2A

As you can see everything looks like it should work. My passwords match and my domain matches but still no joy. After banging my head on my desk to figure this out, I see the below error message at the bottom of my client’s VTP status.

*** MD5 digest checksum mismatch on trunk: Gi0/21 ***

What is this error? What does it mean?

What it means is that the key exchange between the VTP server and client is incorrect and thus no one talks. What it also means is that I am hitting a long running bug. See the Cisco forum post here

If you read that post, you’ll find the fix, but here it is for your reference.

Basically, you need to make your server regenerate its MD5 Checksum value. Once that value is regenerated, VTP messages are exchanged between the server and client(s) and VLAN joy is had by all. To regenerate this value, simply create a new Layer 2 Vlan.  A simple fix for a complex problem. For those of you that want to upgrade code to solve the problem, good luck, Cisco hasn’t fixed this bug in over 20 revisions of IOS software.

I hope this has helped someone, thank you for reading.










Revisiting Cisco Jabber SRV Records

From time to time I like to revisit previously discussed topics, today is the day for Cisco Jabber SRV records. Previously I had written a post talking about internal Jabber SRV records and how to configure and use them. That post is located here for your viewing pleasure.

The truth is that internal SRV records, when it comes to Cisco Jabber, are only half of the story. To tell the whole story, you need to have at least a partial understanding (and hopefully a working knowledge) of Cisco’s Collaboration Edge. If you do not, this will be a bit out of context for you, but the theory is easy enough to understand.

So you have an on premise Cisco IM & Presence installation and you have users on your internal network that are using Cisco Jabber. It is a very powerful business tool; instant messaging, screen sharing/control, and desktop video/voice all from one convenient and surprisingly well built application. What happens when your users leave your internal network? Do they VPN? Do they use WebEx? Or perhaps something less IT friendly? What if they could use Cisco Jabber wherever they are, without the hassle of VPN and securely from any device? The truth is, they can!

In comes Collaboration Edge, it goes by a few other names, but this post isn’t about Collaboration Edge…directly, its about a very handy SRV record that sits on your external DNS server(s) to make the Collaboration Edge integration possible. For a 1000ft view, Collaboration Edge includes two appliances, one on the LAN and one on the Internet or DMZ. These two appliances talk together using magic, pixie dust, tiger blood and SSL certificates (those are the ones that really scare me, but that is for a different post). With these two appliances talking, they are also linked to CUCM and voila’ we have extended CUCM’s capabilities to the information super-highway known as the Internet. It’s certainly not that simple, but you get the idea.

We know from my previous post that Cisco Jabber can discover it’s  network services via DNS SRV records. Internally it can discover both CUCM (for directory services and service profiles) and IM&P (for login and instant messaging, etc.). The process for discovering services outside of the network is very similar, but the differences are worth noting.

Cisco Jabber always searches for the same services i.e. SRV records no matter what network it is on. Whether it is on your internal network or just sitting on the Internet i.e. a home network the discovery is the same.

When you put in your Jabber ID (JID) i.e. Jabber queries the following records based on the domain of your JID.

  • Jabber looks for WebEx Connect (Cloud instant messaging services).
  • Jabber looks for Internal SRV records i.e. cuplogin and cisco-uds (as shown below).

  • If Jabber does not get a response from either of these records it looks for collab-edge which is pointing at the Collaboration Edge – Internet side appliance from earlier (as show below).

The collab-edge record configuration looks like this…   SRV service location:
          priority       = 3
          weight         = 7
          port           = 8443
          svr hostname   =


Assuming that no other records above the collab-edge record answer, Jabber sends its login request to the device attached to SRV record and logs into internal IM & Presence server as well as CUCM and any other services configured in the service profile.

A couple of import things to remember when talking about external DNS. First, some well-meaning DNS administrators will put a catch-all in their external DNS configuration so that anything destined for * goes to their website. This is fine, but it will break your external Jabber connectivity. This break occurs because even though it doesn’t exist will still be caught by the catch-all. Second, collab-edge goes in the external DNS environment only. Just like cisco-uds and cuplogin are only internl, collab-edge is only external. Forgetting or disregarding this will surely make your troubleshooting much more interesting to say the least…

I hope this has been helpful to someone. Cisco Jabber is a power tool and when paired with Collaboration Edge the possibilities are endless. Hopefully some day soon I’ll be able to write a series about Collaboration Edge and its many facets but until then, thanks for reading.


The Upgrade Follies: Communications Manager 9.x to 11.x

If you’ve been in the Cisco voice game for more than a second, you’ve probably done a Call Manager upgrade or two. In my case, I lost count around version 4.1 to 4.3. My record for the longest upgrade that I was a part of is 72 hours…straight! It was painful but such was life back in those days.

With the advent of virtualized Cisco voice and all of its associated parts the upgrades have definitely improved, but that does not mean that the gotchas aren’t still lurking.

For one of my current customer projects I am upgrading a virtualized 9.x environment to 11.x. Unity Connection was upgraded first using CLI. CUC luckily doesn’t have a whole lot of gotchas assuming the engineer that built it originally used an OVA template and followed the correct steps. All you need to do is apply the new “keys” COP file (ciscocm.version3-keys.cop.sgn) and you are good to go. Maybe it isn’t quite that easy, but you get the picture. Communications Manager (Call Manager) is a far different animal. For the sake of automation, I’m doing the CM upgrade using Prime Collaboration Deployment (PCD). PCD is a separate application server that comes with your upgrade order on Cisco’s Product Upgrade Tool (PUT). PCD basically allows you to take a CM cluster (including IM&Presence) and script the upgrade so that you can basically click once and wait. If only it were that easy…

There are a couple gotchas that I’ve learned the hard way. I’ll list them below, hopefully they can help you out during your next upgrade.

  1. Licensing. If you are going to do an upgrade, do your homework. I could write an entire post on licensing but for a 9.x to 11.x upgrade it really just involves doing clean up. If you are getting that ugly little licensing warning from Cisco when you log into your system, clean it up before attempting to upgrade, you’ll save yourself from a lot of pain later.
  2. Disk Space. I get it, hard drive space is cheap, but OVAs are not future proof. The original mid-size build OVA for CM 9.x specified an 80 gig virtual drive. 80 gigs, while small, is not not supported by 11.x installs. What bites engineers in the ass is a pesky little storage location known as the common partition. When the 11.x upgrade script first verifies that an upgrade is possible, it checks the amount space available in that common partition, if less than 25 gigs space is available the upgrade will fail. There is an excellent Cisco Support Forums post about this failure here.  So what does one do if the above scenario is true?

There are 3 options…

  1. You can go into your server’s TFTP directory and manually remove old crap that you don’t need. If you happen to remove crap that you do need, bad things could happen, so keep that in mind….
  2. You can apply the following COP file ciscocm.free_common_space_v1.3.k3.cop.sgn. This little beauty will remove any software tied to the inactive partition of the system which may include software tied to the common partition, thus giving you your required space. This is a really cool idea/theory, but I’ve had mixed results.
  3. This is the scariest sounding one, but its actually not that bad. There is a second COP file that you can run. The ciscocm.vmware-disk-size-reallocation-1.0.cop.sgn this file will allow you to resize your virtual disk in VMWare ESXi and make CM ok with it (I tend to expand 80 gig disks to 160 as long as the physical systems allow it). **Changing the size of the disk without the COP file basically guarantees you a rebuild from scratch and possibly a resume` generating event.** As I said, its not that bad, but there is a catch. In a couple of different cases, your results may vary.

1. If your CM system is running on a snap shot within ESXi, your virtual disk size adjustment option will be grayed out, this will inevitably cause you to panic and wonder if a PCD migration is your only option, its not. You can actually delete the snap shot and once you do that you should be able to change your disk space. Once you do this, restart your VM and let it go through its process. It will reboot 2 times during the start-up process as it expands the disk in the “BIOS” and then in the initial CM boot process” If you’ve done it correctly you’ll see your partitions aligned and your new disk size in both the CLI and web console.

2. In some cases the allocation of your virtual disk may be as large as the blocks with in the disk controller will allow it to be. If this is the case, you have two options. Option 1 (see option 1 above). Options 2, migrate instead of upgrade using PCD. It will take more time but you and/or your customer’s data should be safe and back where it belongs.

Whew… that was a long post. I hope it helps someone. For those of you new to upgrades, you’re lucky, they keep getting easier. If you have questions, leave a comment and we can have a discussion. Thanks for reading!