Converging to a New STP Topology
STP logic monitors the normal ongoing Hello process when the network topology is stable; when the Hello process changes, STP then needs to react and converge to a new STP topology. When STP has a stable topology, the following occurs: 1. The root switch generates a Hello regularly based on the Hello timer. 2. Each non-root switch regularly (based on the Hello timer) receives a copy of the root’s Hello on its RP. 3. Each switch updates and forwards the Hello out its Desi..
As a designer of secure networks, one of the first things you must consider is the vast interdependency of today's larger networks. The Internet is the best example, but within each organization there exists a microcosm of the Internet. From an attacker's perspective, these interdependencies allow for the attacker's goals to be met in any number of ways. As an example, assume an attacker wants to bring down your website. The following list outlines the attacker's options: ..
Four-Step STP Decision Sequence
When creating a loop-free logical topology, Spanning Tree always uses the same four-step decision sequence: • Lowest Root BID • Lowest Path Cost to Root Bridge • Lowest Sender BID • Lowest Port ID Bridges pass Spanning Tree information between themselves using special frames known as bridge protocol data units (BPDUs). A bridge uses this four-step decision sequence to save a copy of the best BPD..
By default, a switch operates in Per-VLAN Spanning Tree Plus (PVST+) mode using traditional 802.1D STP. Therefore, RSTP cannot be used until a different spanning-tree mode (MST or RPVST+) is enabled. Remember that RSTP is just the underlying mechanism that a spanning-tree mode can use to detect topology changes and converge a network into a loop-free topology. The only configuration changes related to RSTP affect the port or link type. The link type is used to determine how ..
Baseline Configuration for EIGRP Redistribution Examples
The best method to see the results of redistribution is to use examples, so this section explains the sample internetwork used in the upcoming EIGRP redistribution examples. Figure 9-6 shows the sample internetwork. In this case, the EIGRP domain on the left uses subnets of class B network 172.30.0.0, and the OSPF domain on the right uses subnets of class B network 172.16.0.0. Note that all OSPF subnets reside in area 0 in this example internetwork, although that is not a re..
