Cisco Wireless Access Points and the Google Chromecast

I recently purchased a few Google Chromecast’s to use for “wireless HDMI” within our business. The Chromecast allows for full screen browser streaming and for $35.00 USD on Amazon ($30.00 at Staples!) it is a great way to share notes during a meeting, project information and multimedia.

Our company leverages Cisco based Access Points for our 802.11n/ac wireless access. Out of the box, I found that Chromecast’s were able to connect but Chrome was unable to “cast” to the devices. Several articles here and here pointed to UPnP (IGMP) as being the issue.

Disabling IP IGMP snooping and the snooping helper within the access points resolved the issue:

no ip igmp snooping
no dot11 igmp snooping-helper

No restart of the Access Point or Chrome device is required after making this change.

Autonomous System Networks (ASN)

Deep in the bowels of the Internet lies a beast, understood by few and feared by many. His name is Border Gateway Protocol, his acronym ‘BGP’ and his presence vital to the stability and redundancy of the Internet. Often referred to as the ‘black magic’ of networking, understanding and utilizing BGP has generally been left to Cisco CCIE’s and other such edu-can’s.

In this article, I’ll give you a crash course on BGP, links to further reading and some nifty tools you can use to understand how various networks are put together.

Border Gateway Protocol (BGP) is the routing protocol used to exchange routing information across the Internet. BGP is an exterior routing protocol and as such is concerned with routing between networks rather than within them (this is the domain of the interior routing protocols such as RIP, OSPF, IS-IS). BGP/4 is defined in RFC 1771. Also see RFC’s 1772, 1773, and 1774.

Each and every network on the Internet is assigned an Autonomous System Number or ASN which identifies the network and provides consolidation of hosts within a single ‘virtual’ infrastructure. For the sake of simplicity, we’ll use Google as our example in the following scenarios:

Google has multiple data centers in multiple locations with some 100,000 production server-end points. In order for Google to operate an accessible and redundancy network, its necessary that they peer (connect) Continue reading “Autonomous System Networks (ASN)”

Tunlr: Access streaming services from anywhere!

Tunlr provides a free DNS proxy service which allows individuals living overseas to access streaming media services in the US and UK as well as several other western countries.

Streaming services supported include:

  • Hulu / Hulu Plus
  • MTV
  • CBS
  • ABC
  • Pandora

How does it work?

Tunlr readdresses various DNS data envelopes sent between your computer and the streaming service provider in order to transparently “trick” the streaming system into thinking you are based in the US or UK.

How do I configure Tunlr?

Configuring your laptop, desktop, iPhone, iPad, Apple TV or other media device is use Tunlr is as easy as configuring your primary DNS server to: and your secondary DNS server to:

Note: These DNS server IP addresses are prone to change. Visit the configuration link below for updated DNS server IP’s.

Instructions for a variety of devices are available here. Once you have made the configuration changes visit the Tunlr status page to confirm that your settings are correct.

OSPF Cheat Sheet

The following are a list of commands and syntax used when working with OSPF.

Show OSPF configuration on the local router or L3 switch:

4510RE-SW1#sh run | b router ospf
router ospf 1
area 0 range
network area 0
network area 1

Show local routes, both static and OSPF. Note: O refers to OSPF defined routes.

4510RE-SW1#sh ip rou
Codes: C – connected, S – static, R – RIP, M – mobile, B – BGP
D – EIGRP, EX – EIGRP external, O – OSPF, IA – OSPF inter area
N1 – OSPF NSSA external type 1, N2 – OSPF NSSA external type 2
E1 – OSPF external type 1, E2 – OSPF external type 2
i – IS-IS, su – IS-IS summary, L1 – IS-IS level-1, L2 – IS-IS level-2
ia – IS-IS inter area, * – candidate default, U – per-user static route
o – ODR, P – periodic downloaded static route

Gateway of last resort is not set is subnetted, 2 subnets
C is directly connected, FastEthernet0/0.410 Continue reading "OSPF Cheat Sheet"

Cisco Switch IOS Recovery

If your Cisco switch flash memory has become corrupt or you have accidentally erased it (read: delete /force /recursive flash:*) and then powered cycled your switch, you may be stuck in boot-loader mode. In short, your switch does not have a internal operating system (IOS) to load.

To recover your switch and restore the IOS you will need to download the latest IOS release from and extract the .bin file from the tarball (.tar) file using 7-Zip, WinZip or your preferred compression application.

The following process will guide you through the IOS recovery and restore process:

1. Use 7-Zip to extract the .bin file from the .tar file on your local computer.

2. Connect to the switch using Tera Term using connection parameters: 9600 baud, 8 N 1.

3. You should see a prompt that says “switch:”. This means you are in boot loader mode.

4. Downloading the .bin file from your computer to the switch at 9600 baud will take a long time (around 3 hours), so we will change the baud rate of the console port temporarily. Enter the command “set BAUD 115200″. After you enter this command, you will see strange characters in Tera Term because its baud rate and the switches are now miss-matched.

5. Close Tera Term and re-connect using 115200 baud instead. You should see the switch: prompt again. Continue reading “Cisco Switch IOS Recovery”