Protocol Filtering and Controlling LAN Floods
Attackers can cause broadcast floods to disrupt communications over the LAN. You saw an example of this in the section "MAC Address Floods and Port Security." Therefore, it is important to control flooding on the switches. There are two main ways to do this: Set up threshold limits for broadcast/multicast traffic on ports Use protocol filtering to limit broadcasts/multicasts for certain protocols Catalyst switches allow thresholds for broadcast traffic to be set up on a pe..
Local-Area Networks and Technologies
Local-area network ( LAN) technologies, as the name suggests, are extremely localized, covering a small geographic area up to only a few thousand meters. For example, they can connect computers within or between buildings, or within a particular department, such as Accounting or Marketing. Whenever there is a situation in which you are able to install your own physical media to connect peripherals, workstations, and terminals, you would employ LAN technologies. Because of the..
A DHCP server normally provides all the basic information a client PC needs to operate on a network. For example, the client might receive an IP address, a subnet mask, a default gateway address, DNS addresses, and so on. Suppose that an attacker could bring up a rogue DHCP server on a machine in the same subnet as that same client PC. Now when the client broadcasts its DHCP request, the rogue server could send a carefully crafted DHCP reply with its own IP address sub..
OSPF can support multiple network types. For example, a multiaccess network such as Ethernet is considered to be an OSPF broadcast network. Table 7-6 shows a listing of supported OSPF network types and characteristics of each.
The Perl script in Example 19-1 parses a router syslog file and builds a detailed report of packets that were denied by logging ACLs. By default, the script will parse every ACL log message that it finds in the syslog file on a server. You can also look for messages associated with a particular ACL by specifying the ACL number or name as a command-line argument. Example 19-1. logscan.pl #!/usr/local/bin/perl## logscan.pl -- a scrip..
