In this post I’ll try to make an educated guess about what happens with Hulc LED process and why it appears to consume 20-30% CPU on Cisco 2960(S/X/XR/RX) switches. (N.B.: the issue appears to be present on Cisco 3750 / 3560 platforms as well) Symptoms If you monitor your switch via SNMP, you may quickly notice constantly elevated… Read More »
Recently, I tested a Cisco 6500 switch in a fan-less configuration, to see how long it can go. DISCLAIMER: DO NOT TRY TO DO IT. This is a stupid idea and it will void warranty / would be a perfectly valid reason for Cisco to decline RMA (in my opinion at least). Running a switch without fans will… Read More »
There is an interesting problem with Cisco 6500 VSS clusters: generally, switchover between nodes is fast enough and only a few packets are lost. NSF&SSO algorithms help a lot to achieve that. But if you configure a feature that doesn’t support SSO for some reason, the flap becomes more noticeable. In this post I’m trying to make an… Read More »
An EtherChannel is a way to use multiple physical interfaces as a single logical one. That logical one appears as a single interface to MAC table, STP and management plane. That solves two main concerns: it adds bandwidth and it prevents STP from considering several parallel links a loop, thus preventing it from being blocked.
Here comes a really tough design question from one of my co-workers: What is a good estimation of the maximum number of hosts per ethernet domain (i.e. VLAN)? Well, when I was first studying networking in college, we generally accepted that about 250 hosts should be the limit and enough for everybody. It was years ago, so let’s… Read More »