General Switch and Layer 2 Security
Some of the basic rules to keep in mind when setting up a secure Layer 2 switching environment are as follows: VLANs should be set up in ways that clearly separate the network's various logical components from each other. VLANs lend themselves to providing segregation between logical workgroups. This is a first step toward segregating portions of the network needing more security from portions needing lesser security. It is important to have a good understanding of what VLAN..
Basic subnetting and variable-length subnets are often misunderstood. This section gives a brief introduction to how subnetting works, and the next section discusses variable-length subnet masks (VLSMs). A subnet, or subnetwork, is a subset of a Class A, B, or C network. To better understand subnetting, it helps to take a closer look at IP addresses that are not subnetted. As explained earlier, IP addresses are comprised of a network portion and a host portion, representing a..
OSPF creates a two-level hierarchy of areas. Area zero (also called the backbone area or transit area) is always the central area; all other areas attach to area zero. Area zero forms the top level in the hierarchy and the remaining areas form the bottom level of the hierarchy. This hierarchical design supports summarization and minimizes routing table entries. Routers in area zero are called backbone routers. Routers that link area zero and another area are cal..
You can use the optional size attribute with the logging buffered configuration command to change the size of your router's internal log buffer: Router#configure terminal Enter configuration commands, one per line. End with CNTL/Z. Router(config)#logging buffered 16000 Router(config)#end Router# Be careful, though, because adjusting the size of the router's logging buffer wipes out all of the current contents of the buffer. The typical default size of a router's log..
Setting Up Frame Relay with Map Statements
In its simplest form, the Frame Relay map configuration involves considerably less typing than the subinterface version of the same configuration: Central#configure terminal Enter configuration commands, one per line. End with CNTL/Z. Central(config)#interface Serial0 Central(config)#description Frame Relay to branches Central(config-if)#ip address 192.168.1.1 255.255.255.0 Central(config-if)#encapsulation frame-relay Central(config-if)#frame-relay map ip 192.168.1.10 ..
