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Tag Archives: networking
Cisco Two or More IP Addresses
I wanted to take an opportunity to share an experience I had recently and explain how I resolved it. The situation I walked into was quite ugly. A small consulting firm had helped install some new switches at a medium sized business. They basically did a rip and replace. Before the replacement the network was configured with four VLANs; One VLAN for IP cameras, IP Phones, a few isolated APs, and of course corporate PC data. The bad news was that the fly-by-night consulting firm had a tech on this job that knew nothing about VLANs. Can you see the … Continue reading
Keeping Time on Cisco IOS
When doing any type of troubleshooting I am big on log files. To get the most out of your log files, however, you need the time stamps to be accurate. For time stamps to be accurate you need to ensure your systems are all running with exactly the same time Continue reading
Posted in Networking Tagged cisco, configuration, IOS, logging, networking, trouble shoot Leave a comment
Cisco Switch Remote SPAN
Capturing network traffic can be a very effective way of solving complicate issues particularly when log files are not yielding useful results. One issue typically is the ability to actually physically perform the capture. To overcome these limitations a Remote SPAN or RSPAN instance can be used. Continue reading
Posted in Networking Tagged cisco, IOS, logging, networking, packet capture, testing, trouble shoot Leave a comment
Prevent IP Access by Routing to Null
The goal of a router is to send network traffic to its destination based on its routing table. Some times its necessary to prevent traffic form flowing through a router. This can typically be achieved with access control lists, but a cost. ACLs, particularly long and complicated ones, come with the cost of performance. When preventing access to an entire subnet it is possible to simply route traffic into a “black hole” where it will be discarded. This is achieved without using an ACL. Continue reading
Posted in Networking Tagged cisco, configuration, IOS, logging, networking, security Leave a comment
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