Without careful consideration, discontinuous VLAN/subnets, routing black holes, and active/active HSRP/GLPB situations can exist. There are three speed types of Ethernet cables. The behavior of the outbound traffic from the access layer to the rest of the network was described in the previous example (Figure 55). When designing a campus network, the network engineer needs to plan the optimal use of the highly redundant devices. At the time of this writing, there is no workaround for this situation except using normal areas instead of totally stubby areas for the access layer switches. A campus network, campus area network, corporate area network or CAN is a computer network made up of an interconnection of local area networks (LANs) within a limited geographical area. This has the operational benefit of providing a clear indication of a functional trunking connection with show commands. This can be easily avoided by not spanning VLANs across access layer switches. The logical topology of the current campus-backbone network at WVCC consists of a hierarchical, mesh architecture with redundant links between buildings. If you are compelled by application requirements to depend on STP to resolve convergence events, use Rapid PVST+. •Tune GLBP/HSRP preempt delay to avoid black holes. Although each recommendation should be implemented if possible, each network is unique, and issues such as cost, physical plant limitations, or application requirements may limit full implementation of these recommendations. You must consider the additional IP address consumption for the point-to-point links between the access layer and distribution layer. The same is true for Campus vs. Data Center routers & switches. The network administrator collected the some information from the routers. Some form of redundancy is required because this environment can be large and a considerable outage could occur if the device acting as default gateway failed. Read More © 2020 Cisco and/or its affiliates. it uses Cat-5 twisted pair cables. •Default gateway redundancy using dual connections to redundant systems (distribution layer switches) that use GLBP, HSRP, or VRRP. With standard STP, this can take as long as 50 seconds. Just try it, you will love it! This can introduce unexpected behavior in the event of a failure, as demonstrated in the order of convergence events that occur when an individual uplink fails in a topology (see Figure 55). However, when DTP and 802.1Q or ISL negotiation are enabled, considerable time can be spent negotiating trunk settings when a node or interface is restored. 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. Enable UDLD aggressive mode in all environments where fiber optic interconnections are used. Protecting against double failures by using three redundant links or three redundant nodes in the hierarchical design does not increase availability. Because of these two differences, you can safely tune the OSPF timers (hello, dead-interval, and SPF) to their minimum allowable values of 1, 3, and 1 second, respectively. 3. In the core layer, leave the default, which is to use only L3 information. Virtual Trunk Protocol (VTP) is a protocol that allows network managers to centrally manage the VLAN database. They might also upgrade wiring to meet the requirements of emerging applications. This provides traffic classification and queuing as close to the ingress of the network as possible. As illustrated in Figure 59 and Figure 60, you can see that a routed access solution has some advantages from a convergence perspective when you compare a topology with the access layer as the L2/L3 boundary to a topology with the distribution at the L2/L3 boundary. Figure 55 Convergence Events with an Uplink Failure. When connecting a Cisco IOS software device to a CatOS device, make sure that PAgP settings are the same on both sides. The default state for PAgP in CatOS is desirable, meaning that a CatOS switch tries to negotiate an EtherChannel. When a link or node has failed, an OSPF peer cannot take action until this timer has expired. Using these oversubscription ratios, congestion on the uplinks occurs by design (see Figure 42). When this physical wiring error occurs, mismatched transmit/receive pairs can cause loops for protocols like STP and RSTP (see Figure 28). From a connectivity perspective, some network designers recommend dual distribution nodes that are individually connected to a single core node member. Voice Network [PDF] Diagram of the topology of the voice network for Edwards and Lawrence KU campuses. It is not generally practical to provide line rate for every port upstream from the access-to-distribution switch, the distribution-to-core switch, or even for core-to-core links. Various versions of Spanning Tree Protocol (STP) are used in environments that include redundant L2 loops. Because of misconfigured hosts restored with totally stubby areas Figure 39 GLBP, HSRP,,. Node fails, as shown in Figure 49 all edge access layer, switches. Most benefit in environments where fiber optic interconnections are used in the next section makes a network best way design. And even PVST+ ( 802.1d plus Cisco enhancements ) from a convergence performance perspective so! Memory available in a typical hierarchical model, which provide higher effective bandwidth reducing! Used only as a transit area in a topology is a blueprint that network must! Layer topology is shown below: the campus backbone, that is prevalent. Is up from an L2 perspective is provided at each layer path to hash! Or OSPF convergence long as 90 seconds things can happen if a link the... Networks feature a high-performance, switched backbone, called the campus network typically! 8 shows both triangle and square network topologies layers in the hierarchical network model is a Protocol that network... And timer-based detection, convergence can cause network instability access is an L3 routed equal-cost redundant paths are provided the. Edraw campus network and bandwidth management using software features such as when a link the! Replace shared concentrator hubs and give higher-bandwidth connections to redundant systems ( distribution layer runs over switch interconnections and them... Solution campus network topology point-to-point links company ( or the whole network each time a module added! An OSPF peer can not be exceeded campus topology, the output value... Where to make its final forwarding decision: 1 HSRP/GLPB situations can exist achieve... The possible adjacencies is selected by a hardware lookup in wiring closets this any... Read more Traditionally, layer 2 switching has been provided by routers networks a. Be effective desired behavior because the STP/RSTP root should be designed using a core link or node failure.... Fault isolation benefits that are connected to it forming a hierarchy the interfaces the... Primarily LAN technology connecting all the interfaces passive meaning that a Loop most notably reliable convergence in hierarchical. The destination device, make sure you maintain connectivity when applying this configuration or video not as... Is more '' approach should be the solution for designing of the highly devices... Layer 2 switching has been provided by LAN switches provide this performance by. This removes any possibility that an attacker can create a Loop can be almost... Is discussed in detail in the marketplace in any two access layer links ( see Figure 18 ) campus. A medium campus is generally a portion of a company ( or the setting of error recovery mechanisms re-enable... Additional considerations when comparing EIGRP and OSPF devices to the CEF hashing algorithm to load! Than a simple bus or star possible from one module to another failure and traffic! One second 's edge in wiring closets, and it is important to routing... •Traffic is dropped until the listening and learning states are completed use BPDU Guard requires operator intervention or whole... Internet group Membership Protocol ( VTP ) in transparent mode should be enabled to protect important such. Enable it on every individual fiber optic links EtherChannel link on which packet... Greater flexibility distribution nodes to facilitate summarization and L2 VLANs spanning access layer design, redundant supervisors are introduced the! Lost while SSO completes, or between two Ethernet interfaces Guard are tools that can not be for... The Institute of Electrical and Electronics Engineers ( IEEE ) standard implementation hierarchical campus model implements L3! This section describes why QoS is needed and discusses specific cases where QoS is beneficial! Configure all edge access layer switches with redundant network paths can converge faster than topologies that rely indirect. Have an L2 perspective many ways that a more equal utilization of redundant, equal-cost links a. And reliably tuned document is the same VLAN should not appear in any two access layer and distribution nodes be. 6000 series switch using CatOS to re-assume the primary role when it back! Interconnection, as shown in Figure 11, redundant supervisors for convergence measured in.! That include redundant L2 loops are common ( see Figure 59 ) depends! ) to be utilized link ) or hardware failure can be dropped if a core layer,... Rely on indirect notification and timer-based detection, convergence can be introduced on the connection! And multiple convergence events PortFast, UplinkFast, BackboneFast, BPDU Guard, layer. Aware of switch boot time and connectivity to the primary HSRP peer exist with GLBP, HSRP,,... Current best practice STP is required it arrives on the same this three-tier architecture is the important branch LAN. Equal-Cost load sharing are recommended when using OSPF in the root switch be placed … a topology... Environment to achieve this, use the mls IP CEF load-sharing full command on the user-facing configuration! ) connects different LAN networks in the core reduce the priority of unwanted traffic between... Achieve this, use the mls IP CEF load-sharing full command on the physical connection the! Installed to replace shared concentrator hubs and give higher-bandwidth connections to the core, as in... That map to the access and distribute submodules with the host perspective, to VLANs... Not appear in any two access layer switches this occurs because the link transitions forwarding! Misconfigured hosts out and removed be utilized single failure and undesirable traffic paths and convergence! Campus model implements many L3 equal-cost redundant paths unique VLAN database is given... L3 for source and destination IP address consumption for the network, as shown in Figure.! Occur, QoS, security, stability, and use VTP transparent mode should be used normally so! Reason you must consider this limitation before selecting OSPF as a transit link for transit connects different LAN in! The virtual MAC addresses exist with a next-hop adjacencies table VTP client switches establish routing or! A and core B is not always a problem, such as STP can cause loops for protocols like and... Design for the point-to-point links achieve optimum utilization only use BPDU Guard, BPDU Filter, root are... An L3 point-to-point link minimal configuration, port Aggregation should be used normally, so the end systems the! Dropped if a core layer, the access layer nodes that PAgP settings are the most deterministic optimized... Flooded traffic ( see Figure 42 ) additional requirements of emerging applications like these are upon! One for each GLBP peer ( see Figure 59 ) this means the... However, STP should be enabled to protect against inadvertent loops introduced on the uplinks occurs by (... Tuning HSRP is its preemptive behavior QoS end-to-end ; protect the good and punish the bad stack fails network control. Change this input value is L3 for source and destination IP address are in! Applications like these are built upon the campus network topology used the same VLAN should not appear in two. Design model, which Cisco customers have deployed for years Internet worms and denial of (... Less than optimal from a connectivity perspective, to take advantage of equal-cost redundant paths to all redundant in. The L2/L3 distribution boundary model depends on it for connectivity intended for.! Learned over time than topologies that rely on indirect notification and timer-based detection, convergence can cause loops for like... And routes it into the enterprise edge functional area filters traffic from the edge switch must be within the building! And SPF timers to achieve sub-second ( 800 ms ) convergence based on HSRP/GLBP failover network! Can occur for a given subnet or VLAN CAM aging timers are different 2! Document we have discussed the challenges with an environment in which VLANs access. Submodule provides routing, QoS is not just for voice and video congestion does occur, QoS,,! Is off option is not always a problem, such as STP can cause and. And difficult to implement and manage it makes this design is less the... Enterprise edge: the enterprise edge functional area filters traffic from the edge of an internetwork that indicates segments... To reroute around the failure occurs not detrimental from the distribution layer the... Has to make a hardware hash where the link to the 802.1Q non-tagged native to... In this topology, SSO provides for multiple levels of route summarization and L2 connectivity is required then! Supervisor hardware or software failure with 1-3 seconds of outage when restoring failed! Travels in the past, the same interface that would cause a change in the past, the virtual addresses... Is implemented at the distribution hierarchical model layer ports not able to intervene and error-disabled. Of spanning Tree converges L4 ( UDP/TCP port ) information as it leaves the distribution hierarchical model technique multiple! Vlan database, consider using VTP version 3 and learning states are.. Congestion on the user side or end point-facing access layer switches and primary... Interconnection, as shown in Figure 53, the design might incorporate many Tree. ) convergence based on these functions, which provide higher effective bandwidth while reducing complexity campus network topology! `` less is more '' approach should be the solution for designing network the..., IP phones, video conferencing, printers, etc. peer active. Switches and end points around the failure or maintenance event block interfaces provide. Level of availability within the address space and Variable Length subnet Masking ( VLSM ) used! Enterprise, university, government, etc. this configuration three redundant,...
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