switching - Parallel Ports are great for controling devices but I want more bits

This is mostly a hardware question but with interesting software implications:Parallel ports are one of the wonders of the age. As well as printing things you can use them to control external devices, for example, by switching reed relays on and off simply by writing the correct word to the parallel port buffer.And they are really cheap. A reliable USB-parallel cable can cost you no more than £5. So you can build a very neat, software controlled system capable of switching 8 things on and off for less than £10 (because there are 8 data bits ava...Read more

switching - How can I modify OSX GUI colors to be more readable for weakened vision

A bit of preface: I'm currently a Windows user but I'm looking into switching to Mac for work purposes. This of course means that I'd be staring at the UI of OSX for about 40 hours every week at least which is significant enough to cause strain to my eyes.What's even worse is that I have weakened vision (essentially a mix of color blindness and snow blindness) which means that the default white/light gray theming of OSX is too bright and not high contrast enough for my eyes. In fact, the default UI is unusable to me.I'm aware of the "poor visio...Read more

switching - Is a 10/100 switch sufficient for Voice?

Seems like a rudimentary question, but I'd like to use an "old" HP Procurve 2610 10/100 switch to provide POE connectivity to a new batch of ~25 deskphones. It appears as though a generic bandwidth requirement is about 100 kbps for each phone/line. Thus, it seems like I should only require ~ 2.5 mbps for all my deskphones to make calls concurrently.Is there any reason to think about using a gigabit POE switch for voice connectivity or should I expect the following solution to work well for such a small office?...Read more

switching - Looping back through switches?

Please look at the attached topologyI am studying for CCNP with ine.com, and I have got a lab switch they say is possible, I say it is not (with the current config)SW-3 configFa 0/15no switchportip address 1.1.1.33Fa 0/14switchport trunk encapsulation dot1qswitchoort mode trunkFa 0/3switchport mode accessswitchport access vlan 111SW-1 configFa 0/15switchport mode accessswitchport access vlan 111Fa 0/11switchport mode access switchport access vlan 111Fa 0/14switchport trunk encapsulation dot1qswitchoort mode trunkSW-2 configFa 0/11no switchporti...Read more

switching - Link Aggregation and Balancing Methods

This might be a silly question, but I am not really sure about how this works.When you form Link Aggregation (or EtherChannel in Cisco terms), the traffic going through that logical port will be load-balanced based on the device setting.For example, in Cisco switches the default will be source mac address based. And you can change that setting in a way that the traffic will be distributed almost equally.So far, it's fine.But how about when the load-balance method is src ip and dst ip but the switch is NOT the server's/client's gateway?For examp...Read more

switching - Force10 MXL switch port mapping

I'm having trouble understanding how blade server internal NIC mapping on the Dell m1000e enclosure when using the Force10 MXL blade switch?So as I understand when two MXL Switches is inserted into the back on the enclosure, 32 tengig internal ports are visible.So if I run #show ip int briThere will be ten0/1, ten0/2 .... till ten0/32And on switch2 ten0/1, ten0/2 .... till ten0/32(Assuming switches are not stacked)So let's say I have three blade servers the mapping would be like this Ten0/1 on the first switch and the ten0/1 on the second switc...Read more

switching - HP A5800 Switch remote port mirror to a virtual host

I have the need to mirror/monitor a port on a HP A5800 AF, but to send the mirrored data for packet capturing to a host which is a virtual server.I'm thinking of having the mirrored traffic dumped on a temporary VLAN which is in the trunk to the ESX host and add that vlan to the guest machine as secondary NIC.From the documentation it seems I can mirror a vlan, but the "monitor" host has to be directly connected to a physical interface.Since this is a remote datacentre I'm currently not in a condition to have a physical machine connected to the...Read more

switching - Blacklist CLI commands on a Nexus

Is there a way to make a Cisco Nexus 7k to reject a CLI command?Everyone knows about the impact, when you want to add a VLAN to a trunk, and if you forget the keyword aadd.If you do this with a VPC N7k pair on a VPC port-channel dot1q trunk, the VLANs will go to suspended as long as they're not allowed on both VPC trunks.Is there a way to make the cli reject the command if you forget the add in: int po[X]switchport trunk allowed vlan add [Y]EDIT:In ios this could be achieved with something likeevent cli pattern [regex] skip yes...Read more

switching - Finding the optimum root bridge for a spanning tree

The spanning tree protocol uses the bridge ID and the MAC address of the switch to elect the root bridge. After the election process, a spanning tree is created, preventing switching loops by assigning port roles like root, blocking, and designated.However, the root bridge selected may not be the optimum root bridge because it's simply selected based on the MAC and the bridge ID. From what I know' the root bridge is supposed to be in the center of a network (literally the center where it can reach all other switches with a least cost) and it sh...Read more