Fixing high CPU use on Cisco 7600/6500

Categories: cisco, network

Recently some time ago (this blog post has also been lying in draft for a while) someone came to me with a problem they had with a Cisco 7600. It felt sluggish and "show proc cpu" showed that the weak CPU was very loaded.

This is how I fixed it.

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The rules of multicast

Categories: cisco, multicast, network

The first rule of multicast is you don't talk about multicast

Most networks don't do multicast routing, which means most network guys don't have much experience with it. Sure they know that it exists, and it's probably used on their layer 2, but they don't do multicast routing. These "rules" list some things that you should know when configuring or troubleshooting multicast.

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Shaping and policing on Cisco

Categories: cisco, network, qos

This post is about policing and shaping on Cisco routers and switches. This is a very big topic so don't expect this post to cover everything. What I'm attempting to to is cover some things that I found aren't explained very well by books or the Internets, while still being readable for someone who hasn't read all the other stuff.

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Spanning tree limits

Categories: cisco, network, spanning-tree

I'm compiling a list of spanning tree and VLAN limits on different switches. This is what I've come up with so far. I don't have an authoritative source for these, but in many cases this is hard to get from specs.

If you go over these limits, bad things will happen! (broadcast storms, VLANs disappearing, cats and dogs living together. That sort of thing)

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What should have been default on Cisco devices

Categories: cisco, network

Some things on Cisco switches and routers never should have been on by default. Other things should have been turned on or set differently. This is not how I want them to be configured in the end (I like CDP for example), just how I think they should have been configured from the factory.

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Erlang BGP daemon

Categories: bgp, bugs, cisco, coding, erlang, network

I'm writing a BGP daemon in Erlang. It can connect, parse update packets and announce routes.

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