Layer 3-Switched Multicast Packet Rewrite
When a multicast packet is Layer 3 switched from a multicast source to a destination multicast group, the PFC and the DFCs perform a packet rewrite that is based on information learned from the RP and stored in the adjacency table. For example, Server A sends a multicast packet addressed to IP multicast group G1. If there are members of group G1 on VLANs other than the source VLAN, the PFC must perform a packet rewrite when it replicates the traffic to the other VLANs (the sw..
Determining All Subnets of a Network—Binary
Another common question, typically simply a portion of a more challenging question on the CCIE written exam, relates to finding all subnets of a network. The base underlying question might be as follows: Given a particular class A, B, or C network, and a mask/prefix length used on all subnets of that network, what are the actual subnet numbers? The answers can be found using binary or using a simple decimal algorithm. This section first shows how to answer the question using..
The steps for configuring RIPng are the same as RIPv1 and v2: Create the routing process, enable the routing protocol on interfaces, and perform any desired customization. The commands, however, are very different. In fact, the creation of the routing process and enabling the routing protocol on the first interface is accomplished in one step, using an interface command. The case studies for RIPng will be similar to those of RIPv1 and v2 to illustrate the similarities in the ..
Business Priorities Must Come First
A university I once worked with decided it was time to allow the student body and faculty wireless access to the campus network. The convenience of access, cost reduction in wiring buildings, and potential productivity increase were the overarching business drivers for the decision. At first blush, however, the security department was reluctant to proceed. For years, the university did not require students to have accounts to access the network. Rather, authentication was re..
In 802.1D, BPDUs basically originate from the root bridge and are relayed by all switches down through the tree. Because of this propagation of BPDUs, 802.1D convergence must wait for steady-state conditions before proceeding. RSTP uses the 802.1D BPDU format for backward compatibility. However, some previously unused bits in the Message Type field are used. The sending switch port identifies itself by its RSTP role and state. The BPDU version also is set to 2 to distinguish..
