- 1.1.3 Broadcasts and Multicasts 1.2 The New Campus Network. - 1.4.1.5 Multi-Layer Switching (MLS) 1.4.2 The Cisco Hierarchical Model. - 1.5.1 The Switch Block 1.5.2 The Core Block. - Controlling Access in the Campus Environment. - 12.2.3.2 The Traceroute Command 12.2.3.3 Network Media Test Equipment. - Verifying existing flow entries in the MLS cache. - Configuring the switch devices to improve Spanning Tree Convergence in the network. - As more users were attached to the hubs used in the Ethernet network, performance of the network became extremely slow.. - Deterministic failover, i.e., the network design must have provisions which ensure that the network stays up and running even if a link fails.. - Scalable size and throughput, i.e., the network infrastructure must be able to handle the new increase in traffic as users and new devices are added to the network.. - FIGURE 1.1: The Open System Interconnection (OSI Model. - The Network layer of the OSImodel defines a logical network address. - Layer 2 switching has helped develop new components in the network infrastructure. - The IP source/destination address in the Network layer header;. - The Protocol filed in the Network layer header. - At the top of the hierarchy is the core layer. - It is literally the core of the network and is responsible for switching traffic as quickly as possible. - If there is a failure in the core, every all user can be affected. - The following Cisco witches are recommended for use in the core:. - 1900/2820 and 2900 Catalyst switches can be used in the switch block. - Routing protocols determine paths and maintain the operation of the core. - You must pay attention to the overall design of the routers and routing protocols in the network. - The size of the network, i.e., the number of routers, then affects routing protocol performance, as updates are exchanged and network convergence takes place. - In a campus network, Gigabit Ethernet can be used in the switch block, the core block, and in the server block. - In the switch block, it is used to connect access layer switches to distribution layer switches. - In a campus network, 10Gigabit Ethernet can be used in the switch block, the core block, and in the server block. - cable, pairs 2 and 3 on one end of the cable are reversed on the other end.. - Cisco also recommends that VLANs not extend beyond the Layer 2 domain of the distribution switch, i.e., the VLAN should not reach across the core of a network and into another switch block. - The VLAN information is carried in the Security Association Identifier (SAID) field of the 802.10 frame.. - If VLANs need to be added back to the trunk, they can be specified as the vlan_range in the set trunk command.. - Instead, frames are forwarded on a specific link as a function of the addresses present in the frame. - A transparent bridge operates in the following manner:. - and the Topology Change Notification (TCN) BPDU, which is used to announce changes in the network topology.. - The latter is used to identify the source of the BPDU message.. - the Root Bridge ID announced in the BPDU. - The Root Bridge election is also based on the idea that the Root Bridge can become a central hub that interconnects other legs of the network. - The Root Bridge and the secondary Root Bridge should be placed near the center of the network.. - The switch has now determined which of its ports is the closest to the root—the Root Port.. - On a CLI-based switch, the port cost can be modified by using one of the following commands:. - This condition lasts for the sum of the Forward Delay and the Max Age.. - In the Core layer, a different method is used to shorten STP convergence. - The ATM reference model is composed of the following ATM layers:. - A CRC value is added to the end of the pre-segmented frame. - The ATM layer and the ATM adaptation layer (AAL) is roughly analogous to the data link layer of the OSI reference model.. - Physical layer, which is analogous to the physical layer of the OSI reference model. - To begin, an LEC needs to find the ATM address of the LECS. - The NSAP address of the LECS can be manually configured into every ATM switch in the network. - The BUS should therefore always be configured on the most robust Catalyst switch in the network, so that its function does not hamper other switching duties of the switch.. - These options are primarily based on the type of connectivity between the switches and the router, and location of the route processor.. - Use the show module command on a Catalyst switch to get a listing of the installed modules.. - By way of the physical connection, the router interface inherits the VLAN identity of the switch port.. - assign a network address to the interface. - The show module command displays a list of the installed modules. - MLSP uses the Cisco Group Management Protocol (CGMP) multicast address, which ensures interoperability with the Cisco switches in the network, as the destination address of the Hello message. - The MLS-SE records the addresses of the MLS-RPs in the MLS-SE content-addressable memory (CAM) table.. - The MLSP management interface can be any MLS interface connected to the switch. - This command identifies each MLSP-RP to the switch by both the MLS ID and MLS IP address of the route processor. - The MLS ID is the MAC address of the route processor. - To adjust the value of the aging time you can use the following command in privileged exec mode:. - the number of active MLS entries in the cache. - Use the following command in privilege exec mode to display the contents of the switch inclusion list to determine which MLS-RPs are participating in MLS with the MLS-SE:. - If the router that is the default gateway fails, the device is limited to communicating only on the local subnet and is disconnected from the rest of the network. - A failure of the active router would result in a switch to the standby router, and packets would continue to be forwarded. - The IP address of a group is in the range of addresses belonging to the subnet in use on the LAN.. - 9.3 HSRP Operations 9.3.1 The Active Router. - The IP address and corresponding MAC address of the virtual router is maintained in the ARP table of each router in an HSRP standby group.. - The function of the active router is to forward packets sent to the virtual router. - a State field, which describes the current state of the router sending the message. - All routers begin in the Initial State. - In the Speak State, the router sends periodic hello messages and is actively participating in the election of the active and standby router. - However, a router cannot enter the speak state unless the router has the IP address of the virtual router.. - In the Active State, the router is currently the active router.. - When a tracked interface becomes unavailable, the HSRP priority of the router is decreased. - Use the following command in privileged exec mode to display the status of the HSRP router:. - Only the 23 least-significant bits of the IP multicast group are placed in the frame. - Multicast control in Layer 2 switches can be accomplished by defining Virtual LANs (VLANs) to correspond to the boundaries of the multicast group. - Each host on the Internet has an address that identifies the physical location of the host.. - Use the following command in global configuration mode to configure the address of the RP:. - Use the following command in the relevant interface configuration mode to configure the multicast router to join a particular multicast group:. - This chapter covers some of the preventative security measures that can be implemented in a Cisco campus environment. - Many of the network device access policies should be the same as the access layer.. - controlling direct access to the device. - For this reason, the network devices of the access layer are physically the most vulnerable.. - Most of the access control policy would be implemented at the distribution layer. - and defining which services the switch block will advertise out to the rest of the network.. - Many of the access control methods used at the distribution layer rely on the creation of an access control list. - These include: applying the access list to the interface for traffic management purposes through the use of the protocol access-group command. - managing routing update information through the use of the distribution-list command. - Depending on which routing protocol is used, a summarized entry of all the available routes of the switch block can be sent from the distribution layer to the core.. - interface_name , which specifies the name of the interface.. - An IP address can be assigned to the Cisco switch for management purposes. - Once the address is in place, you can direct Telnet to access the IP address of the switch to reach the CLI.. - You can also use the IP address of the switch to access an SNMP agent, such as CiscoWorks 2000.. - this allows a network manager to use Telnet from the CLI of the switch to other devices on the network. - Excessive noise Use the show interfaces ethernet EXEC command to determine the status of the router’s Ethernet interfaces. - Check the diameter of the network and make sure it is within specification.. - ip_address The IP address or IP alias of the host.. - 12.2.3.2 The Traceroute Command. - -t tos Specifies the TOS to be set in the IP header of the outgoing. - data_size Number of bytes, in addition to the default of 40 bytes, of the outgoing datagrams
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