ACLs can degrade a router's performance. The effect of processing ACLs on a busy router can be significant. Here are some of the rules you should keep in mind while implementing ACLs on a router so as to minimize their impact on performance: ACLs are processed in a top-down manner. The packets are inspected first against the topmost entry in the access list, and then the access list is worked downward until a hit is made. (If no hit is made on an ACE in the access list, the..
Determining Whether the LSP in the Database Is Valid
The LSP contains three fields that help determine whether the LSP that has been received is more recent than that held in the database, and whether it is intact or has been corrupted. These three fields are as follows: • Remaining Lifetime— This is used to age-out old LSPs. If an LSP has been in the database for 20 minutes, it is assumed that the originating router has died. The refresh timer is set to 15 minutes. If the lifetime expires, the LSP has the con..
Routers cannot simply use logic by which they receive a multicast packet and then forward a copy of it out all other interfaces, without causing multicast packets to loop around the internetwork. To prevent such loops, routers do not forward multicasts out the same interface on which they were received. Multicast routers use a reverse-path-forwarding (RPF) check to prevent loops. The RPF check adds this additional step to a dense-mode router’s forwarding logic: Look at the ..
802.1Q: VLANs and Vendor Interoperability
Because vendors took individual approaches to create VLANs, network administrators were impaired whenever multiple vendor solutions were introduced into their system. A multi-vendor VLAN must be carefully handled to deal with interoperability shortcomings. Recognizing this deficiency in the industry, IEEE commissioned the 802.1Q committee to develop a vendor-independent method to create interoperable virtual bridged local area networks. IEEE 802.1Q describes concepts called ..
An AP can provide WLAN connectivity to only the clients within its range. The signal range is roughly defined by the AP’s antenna pattern. In an open-air setting, this might be a circular shape surrounding an omnidirectional antenna. At least the pattern will appear as a circle on a floor plan—keep in mind that the pattern is three-dimensional, also affecting floors above and below, in a multilevel building. The AP’s location must be carefully planned so that its range..
