Category: Networking
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Second Line On Cisco ATA 186/188
Cisco ATAs have a second line, but you may have also noticed that there is no phone button template that includes two lines for an ATA 186…interesting. It turns out that the second line on the ATA has a completely seperate MAC address associated with it. To use the second line you add it as…
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Is ARP Considered Layer2 Or Layer3
I was discussing an issue with a customer the other day when he told me that layer3 was working because ARP was functioning. I told him that ARP is a layer 2 service that assists layer 3. He told me “you are wrong, but whatever.” 🙂 I didn’t argue. This customer is always abrupt and…
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Block RFC-1918 Spoofed Traffic
A general rule of thumb in a service provider network is to block RFC-1918(private addressing) address space. You want to block this incoming from your upstream providers also, but generally filtering it in your network is a good idea. You will also want to block any traffic coming from your provider sourced from your address…
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Cisco – Troubleshoot POS Interface
Troubleshooting a POS(Packet Over Sonet) interface is quite different than your standard ethernet interface. The first thing you will obviously do is a: show interface POS1/0/0 If you are down/down then you obviously aren’t seeing light across the link and you need to troubleshoot accordingly. If you see the link as up/down, then you are…
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Wireless Transparent Bridging With WDS
WDS(Wireless Distribution System) is a means to transparently bridge wireless APs. What exactly does transparent bridging mean? A transparent bridge is basically turning your wireless links into an ethernet cable. It takes anything put into one side and spits it out on the other. This is great for connecting two locations. This is often used…
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Manipulating OSPF Path Selection With Cost
My good friend JJ asked me a question the other day about OSPF path selection. It was something like “I have a redundant network and I want to adjust cost on an individual route…how do I do that?” Seems pretty straight forward, right?…not exactly. Cost is the metric OSPF uses to judge a path’s feasibility.…
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Cisco RPS (Redundant Power Supply)
If you have Cisco switches you may have noticed that there is a little plate covering something on the back. This something would be the RPS port. Cisco has a few devices, RPS’, used to backup your standard power. If the power supply in your switch malfunctions, the RPS will kick in and provide power.…