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Anyone who has ever done anything remotely "interesting" with a run-of-the-mill broadband router is undoubtedly familiar with the concept of port forwarding. In the case of some applications (<acronym title="Peer-to-Peer">P2P</acronym> comes immediately to mind, but the <acronym title="Real-time Transport Protocol">RTP</acronym> part of <acronym title …
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This is an example configuration showing how to forward the ports necessary to make Blizzard's World of Warcraft Updater work properly with a Cisco IOS-based NAT firewall. Please note that any word-wrapping is a matter of formatting and will not occur when pasted directly to your router.
In this …
Posted on in Networking
If you've spent any amount of time in Cisco networking with Catalyst switches, you've probably run across a port that is in err-disabled state. The most likely place to find this is in the output of show interfaces status. A switch port can end be error disabled if the software …
Posted on in Networking
For those new to Cisco networking, it is often difficult to remember that changes to a Cisco network device are applied immediately. After all, it seems reasonable to assume that changes should need to be applied, just like clicking the 'Apply' button on a Netgear wireless router. Unfortunately, that is …
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Ars Technica recently discussed the effect YouTube has had on the popularity of P2P networking. According to a study done by Ellacoya Networks, HTTP traffic has surpassed <acronym title="Peer-to-peer">P2P</acronym> protocols as the dominant form of Internet downloads for the first time in four years.
Considering my recent …
Posted on in Networking
Robin Gareiss of Nemertes Research has a put together a nice list of questions for potential WAN providers. Most of the questions are focused on non-technical issues like billing and customer service. In fact, the most technical question in the list is
- How many classes of service do you provide …
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If you are using your Cisco Catalyst switches to insert DHCP Option 82 information and you are also using your Cisco routers as DHCP relay-agents (via 'ip helper-address'), you'll notice right away that your Option 82 enabled DHCP requests are not being forwarded by your routers.
As a security measure …
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If you've ever needed to reset a Cisco Catalyst switch to it's factory default (locked out, perhaps?), you've probably spent some time digging around on Cisco's web site. The Catalyst password recovery procedure starts off by reseting the Catalyst to it's original factory settings. Below, I'm going to give you …
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If you're interested in DHCP Option 82 ("DHCP Relay Agent Information Option") in your Cisco Catalyst-based network, you'll be happy to know that the configuration can be summed up in 4 easy steps.
Posted on in Networking
How many times has this happened to you?
SLAP#write memory
startup-config file open failed (Device or resource busy)
If you work in an environment where multiple users have enable access on Cisco devices, you've probably seen it more than once. This particular error is caused when another user has …
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