November 2010

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Sniffing on a switch

I’m an IP network engineer. When something goes wrong, the first thing I do is sniff packets. Got a SIP phone that won’t register? Forget reading logs; sniff 5060/udp and read the SIP chatter directly. A customer complains that “Yahoo chat doesn’t work”? Sniff 5050/tcp and look for TCP hangups, login failures, or ICMP “port unreachable” messages.

Sniffing is easy when you have access to the intermediate router, but that isn’t always the case. What if you’re just another PC on the same switch? That’s impossible, right?

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OpenWRT 10.03.1-rc4 has just been released, so I’m once again upgrading my Buffalo WZR-HP-G300NH home router. Each release candidate in the 10.03.1 series has improved performance of the Atheros wireless chipset, but I still see occasional network interruptions when the laptop is idle overnight. How does wireless on rc4 stack up against rc3?

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