One of the most confusing aspect of setting up an IPS can be the cabling. Different vendors have different cabling requirements and in many organizations different teams control the different devices that may be connected to the IPS. Some vendors recommend using cross-over cables when connecting devices such as firewalls and routers. This is not usually needed if you are configuring the interfaces to Auto/Auto. Most vendors support auto-mdix and auto-mdix automatically detects the cable type and configures the connection appropriately. The works as long as the interfaces speed and duplex are set to auto/auto.

Problems can arise though when you use straight cables and then change the interfaces to a hard set speed and duplex. What worked with Auto/Auto now does not work and the interfaces do not connect resulting in down time. I have seen this happen in a production network and the result was not good.

Some ways to prevent this is to use the cabling requirements as if the interfaces were hard set to a speed and duplex even if they are left in auto/auto. If the interfaces are changed later then you should not have to change the cabling. Make sure if using aut0/auto that the switch ports are configured to use port fast. This ensure the ports reactivate quicker if they become connected. This will ensure any bypass units activate quicker and downtime is reduced.