For example, by default, the Windows XP Home Networking Wizard bridges together all the interfaces on the machine. Operational resiliency: Enables resiliency capabilities to the next level, providing complete network availability even during planned network outages using In Service Software Upgrade (ISSU) features. This model reduces peering relationships and interface count at the core. If inferior BPDUs that would cause an STP or RSTP convergence are detected, all traffic is ignored on that port until the inferior BPDUs cease. The defaults are different. Traffic returning through the standby HSRP, VRRP, or alternate/non-forwarding GLBP peer can be flooded to all ports in the target VLAN when you use a topology in which VLANs are spanned across multiple access layer switches. In this topology, the CAM table entry ages out on the standby HSRP router. Common Campus network Hierarchical Design Models Cisco’s hierarchical network design model breaks the complex problem of network design into smaller and more manageable. In the campus topology, that is the access layer. •Default gateway redundancy using dual connections to redundant systems (distribution layer switches) that use GLBP, HSRP, or VRRP. The following are general design considerations: •Use HSRP or GLBP for default gateway redundancy (sub-second timers). Rapid PVST+ is far superior to 802.1d and even PVST+ (802.1d plus Cisco enhancements) from a convergence perspective. The difference between a WAN router and a campus switch is the number of interfaces and the amount of memory associated with each. The end result is that a more equal utilization of the uplinks is achieved with minimal configuration. Your enterprise can take advantage of these lessons to implement a network that will provide the necessary flexibility as the business requirements of your network infrastructure evolve over time. First, OSPF implements an SPF timer that can not currently be tuned below one second. You can create channels containing up to eight parallel links between switches. Otherwise, multiple convergence events can occur for a single failure and undesirable traffic paths are taken after the spanning tree converges. Advances in routing protocols and campus hardware have made it viable to deploy a routing protocol in the access layer switches and use an L3 point-to-point routed link between the access and distribution layer switches. Link up/down topology changes can be propagated almost immediately to the underlying protocols. Figure 22 Multiple VLANs on a Single Interconnection. Preemption is the desired behavior because the STP/RSTP root should be the same device as the HSRP primary for a given subnet or VLAN. BPDU Guard requires operator intervention or the setting of error recovery mechanisms to re-enable the error-disabled port. In the 3750 family of stackable switches, you can create a cross-stack channel where members of the EtherChannel exist on different members of the stack, yielding very high availability. If you require a common, centrally-managed VLAN database, consider using VTP version 3. Preemption causes the primary HSRP peer to re-assume the primary role when it comes back online after a failure or maintenance event. Following the hierarchical network model is essential for achieving high availability. This document is the first in a series of two documents describing the best way to design campus networks using the hierarchical model. Eventually, the indirect failure is detected by Access-b, and it removes blocking on the link to the standby HSRP peer. There are two specific ways in which OSPF is limited. As it shown in the figure above, a typical large Cisco modular Campus network consists of the fowling building blocks: It provides a very limited set of services and is designed to be highly available and operate in an always-on mode. Figure 62 Primary Distribution Node Restoration. However, a routed access layer topology is not a panacea. The distribution switches become ABRs with their core-facing interfaces in area 0 and the access layer interfaces in unique totally stubby areas for each access layer switch. As stated earlier, this problem only occurs in a topology where VLANs span multiple access layer switches in a large L2 domain. For more detail about cisco data cneter switches refer to the following link: When redundant paths are present, failover depends primarily on hardware link failure detection instead of timer-based software failure detection. For small and medium data center the collapsed design model ( two-Tier) can be used without the need to a dedicated data center core, Using Cisco's next generation data cneter switches “Nexus Series Switches” can significantly improve the performance, reliability and redundancy of the data center by providing,,,, •Client—Receives updates but cannot make changes. Results vary depending on the size of the L2 domain supported by the distribution pair. If there is an L2 interconnection between the distribution switches, then you must consider the STP/RSTP root and link cost so that the correct interfaces are placed in a blocking state. This document presents recommended designs for the campus network, and includes descriptions of various topologies, routing protocols, configuration guidelines, and other considerations relevant to the design of highly available and reliable campus networks. •Assign the native VLAN to an unused ID or use the Tagged Native VLAN option to avoid VLAN hopping. In the hierarchical model, the core and distribution nodes are connected by point-to-point L3 routed fiber optic links. The distribution layer aggregates nodes from the access layer, protecting the core from high-density peering (see Figure 3). The basic principles of the Borderless switched network are the following: 1. hierarchical network Design 2. Recommend correcting if you have the opportunity. •Deploy QoS end-to-end; protect the good and punish the bad. Another alternative is to configure both ends of the trunk to desirable. In a test environment using a typical IP addressing scheme of one subnet per VLAN and two VLANs per access switch using the RFC1918 private address space, the default L3 algorithm provided about one-third to two-thirds utilization. EtherChannels are typically deployed between the distribution-to-core and core-to-core interconnections where increased availability and scaled bandwidth are required. The convergence time required to reroute around a failed access-to-distribution layer uplink is reliably under 200 milliseconds as compared to 900 milliseconds for the L2/L3 boundary distribution model. Software can now tag all native VLAN to an unused ID or use the native! Will change the input into the CEF hashing algorithm to improve load distribution because they provide –Faster... An unexpected spanning-tree convergence is required to protect mission-critical applications such as when a switch block distribution (. 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