The TCP MD5 Signature Option, defined in RFC 2385 [], is used to help BGP protect itself from spoofed TCP segments and, particularly, TCP resets. The TCP MD5 Signature Option employs MD5's message digest algorithm, defined in RFC 1321[]. More details regarding the usefulness of the TCP MD5 Signature Option can be found in the specification. The extension provides a mechanism for TCP to carry a digest message in each TCP segment, where the digest utilizes information known on..
The Foundation Summary provides a convenient review of many key concepts in this chapter. If you are already comfortable with the topics in this chapter, this summary might help you recall a few details. If you just read this chapter, this review should help solidify some key facts. If you are doing your final prep before the exam, the following lists and tables are a convenient way to review the day before the exam. IP addresses are • 32-bit numbers (written as four bytes)..
Appliance-Based Network Services
Just about anything these days can be sold as an "appliance." The point, from a marketing perspective, is to promote the fact that the system is easy to use and requires little intervention from the operator. Just like your toaster, you just push down the lever and it works. TIP I like the appliance model but offer one caveat. If your appliance is really just a Linux box in a fancy case, you haven't solved your system management problem; you've just hidden it under the cove..
The following commands configure various types of banners on a router: Router1#configure terminal Enter configuration commands, one per line. End with CNTL/Z.Router1(config)#banner exec # This is an exec banner #Router1(config)#banner login # This is a login banner #Router1(config)#banner motd $ This is a motd banner $Router1(config)#endRouter1# Notice that the router accept almost any delimiter character, as long as the start and end delimiter is iden..
AutoQoS is an extremely useful feature that can take a lot of the mystery out of building a QoS policy. Unfortunately, there are several restrictions on this feature that you need to be aware of. First, it is only available on point-to-point links between routers. This includes point-to-point subinterfaces on ATM and Frame Relay PVCs, as shown in the example. The feature is also available on PPP and HDLC Serial connections. It cannot be used on any multiple access media, inc..
