VRRP is the logical choice when interoperability with a non-Cisco device is required. The additional link between the distribution switches is required to support summarization of routing information from the distribution layer towards the core. Dynamic Trunk Protocol (DTP) runs over switch interconnections and allows them to form a trunking interface. •EIGRP provides for multiple levels of route summarization and route filtering that map to the multiple tiers of the campus. Get validated design guidance on our open, software-driven approach to deploy a digital-ready network. Figure 57 Best Practice Topology for Spanning VLANs Across Access Layer Switches. •Traffic is dropped until the MaxAge timer expires and until the listening and learning states are completed. The second scenario presents a problem. Each specific index is associated with a next-hop adjacencies table. Campus network design concepts include small networks that use a single LAN switch, up to very large networks with thousands of connections. Figure 32 Port Aggregation Protocol Operation. From the perspective of the access layer, at least three sets of redundant links are traversed to another building block, such as the data center. Smart Campus Network Design (SCND) is the proposed method to design campus network by integrate IoT device with networking device, to facilitate different activities in campus network. These areas allow network designers and engineers to associate specific network … This capability facilitates troubleshooting, problem isolation, and network management. •L3 in the access is an emerging and intriguing option. Without this logical grouping, STP/RTSP would place the redundant interface into blocking state to maintain a loop-free topology (See Figure 30). The basic principles of the Borderless switched network are the following: 1. hierarchical network Design 2. Distinct building blocks can be put in-service and taken out-of-service without impacting the rest of the network. This behavior caused a considerable amount of traffic being dropped; more than 40 seconds in the tested topology. The second document, High Availability Campus Recovery Analysis, provides extensive test results showing the convergence times for the different topologies described in this document, and is available at the following website: http://www.cisco.com/en/US/docs/solutions/Enterprise/Campus/HA_recovery_DG/campusRecovery.html. These can easily happen by accident because of misconfigured hosts. –As a configurable alternative, one of the possible adjacencies can also be selected by a hardware hash using L4 port information in addition to the packet source and destination IP address. Designing a campus network may not appear as interesting or exciting as designing an IP telephony network, an IP video network, or even designing a wireless network. Return path traffic is also in the sub-200 milliseconds of convergence time for an EIGRP re-route, again compared to 900 milliseconds for the traditional L2/L3 distribution layer model (see Figure 61). •Inline power (POE) for IP telephony and wireless access points, allowing customers to converge voice onto their data network and providing roaming WLAN access for users. The following configuration examples show how to enable UDLD for CatOS and Cisco IOS software. There are two specific ways in which OSPF is limited. Cisco switches let you tune the hashing algorithm used to select the specific EtherChannel link on which a packet is transmitted. •Set hello and dead timers to 1 and 3, respectively. When considering core topologies, it is important to consider the benefits of topologies with point-to-point links. To run a routing protocol between the access layer switches and the distribution layer switches, select the routing protocol to run and determine how to configure it. As stated earlier, this problem only occurs in a topology where VLANs span multiple access layer switches in a large L2 domain. BDPU Guard requires operator intervention if an unauthorized switch is connected to the network, and Root Guard protects against a switch configured in a way that would cause STP to converge when being connected to the network. As shown in Figure 6, the hierarchical network model consists of two actively forwarding core nodes, with sufficient bandwidth and capacity to service the entire network in the event of a failure of one of the nodes. This tuning can save seconds of outage when restoring a failed link or node. Figure 51 illustrates a redundant topology where a common VLAN is shared across the access layer switches. NSF/SSO provide the most benefit in environments where single points of failure exist. Additionally, you can use QoS to reduce the priority of unwanted traffic. Cisco Validated Designs (CVDs) provide the foundation for systems design. Recommend correcting if you have the opportunity. The enterprise campus architecture can be applied at the campus scale, or at the building scale, to allow flexibility in network design and facilitate ease of implementation and troubleshooting. A shorter ARP cache timer causes the standby HSRP peer to ARP for the target IP address before the CAM entry timer expires and the MAC entry is removed. It breaks the complex problem of network design into smaller and more manageable areas. •Disable Trunking/VLAN tagging on host ports with the following commands: Note The set port host macro disables EtherChannel, and enables STP PortFast in addition to disabling trunking. This guideline will discuss some of the technologies and design considerations that need to be taken into account during the planning and design phases to design a scalable campus network, Although this guideline is generated based on Cisco’s recommendations and best practices, however it is not a Cisco’s official document. The campus wired LAN enables communications between devices in a building or group of buildings, as well as interconnection to the WAN and Internet edge at the network … These larger networks generally comprise WAN access, a core, an aggregation layer and an … The distribution layer aggregates nodes from the access layer, protecting the core from high-density peering (see Figure 3). Layer 3 routing protocols are typically deployed in the core-to-core and core-to-distribution layers of the network, and can be used all the way to the access layer. However, some additional complexity (uplink IP addressing and subnetting) and loss of flexibility are associated with this design alternative. The campus network, as defined for the purposes of the enterprise design guides, consists of the integrated elements that comprise the set of services used by a group of users and end … The Cisco borderless switched network primary need is availability, flexibility, security, and manageability. HSRP and VRRP with Cisco enhancements both provide a robust method of backing up the default gateway, and can provide sub-second failover to the redundant distribution switch when tuned properly. •Deploying the L2/L3 Boundary at the Access Layer. Similarly to the core, the distribution layer is engineered with sufficient bandwidth and capacity so that the complete failure of one of the distribution nodes does not impact the performance of the network from a bandwidth or switching capacity perspective. Networking for a medium campus is designed for high availability, performance, and manageability. Otherwise, multiple convergence events can occur for a single failure and undesirable traffic paths are taken after the spanning tree converges. Following the hierarchical network model is essential for achieving high availability. This provides fast failover from one switch to the backup switch at the distribution layer. If you must implement a topology where VLANs span more than one access layer switch, the recommended work-around is to tune the ARP timer to be equal to or less than the CAM aging timer. Some of the factors that can be considered for slecting an IGP for a campus LAN: For more details refer to the following link, cisco Borderless campus design, routing resign principles: http://www.cisco.com/en/US/docs/solutions/Enterprise/Campus/Borderless_Campus_Network_1.0/BN_Campus_Technologies.html#wp1053601. Figure 14 Summaries Stop Queries at the Core. Typical traffic flows in the campus cross multiple redundant paths as traffic flows from the access layer across the distribution and core and into the data center. At the very least, this model requires redundant core and distribution layer switches with redundant uplinks throughout the design. However, traffic can be dropped if a core link or node fails, as shown in Figure 10. •Avoid L2 loops and the complexity of L2 redundancy, such as Spanning Tree Protocol (STP) and indirect failure detection for L3 building block peers. Careful consideration should be given as to when and where to make an investment in redundancy to create a resilient and highly available network. A specific situation can cause considerable periods of packet loss during channel negotiation when mixing CatOS in the access layer and Cisco IOS software in the distribution layer. The distribute list allows only the default route (0.0.0.0) to be advertised to the access layer nodes. 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. When the CAM entry has aged out and is removed, the standby HSRP peer must forward the return path traffic to all ports in the common VLAN. •Operating system high-availability features, such as Link Aggregation (EtherChannel or 802.3ad), which provide higher effective bandwidth while reducing complexity. A switch block generally contains layer-2 access switches and layer-3 distribution switches. This provides traffic classification and queuing as close to the ingress of the network as possible. Only use BPDU Guard if you are able to intervene and re-enable error-disabled ports. The throttles that OSPF places on LSA generation and SPF calculation can cause significant outages as OSPF converges around a node or link failure in the hierarchical network model. Unless you vary the decision input for the CEF hashing algorithm at the core and distribution layers, CEF polarization can result in under-utilization of redundant paths. Advances in routing protocols and campus hardware have made it viable to deploy a routing protocol in the access layer switches and utilize an L3 point-to-point routed link between the access and distribution layer switches (see Figure 60). Typically deployed as a pair of L3 switches, the distribution layer uses L3 switching for its connectivity to the core of the network and L2 services for its connectivity to the access layer. For the VMDC version "2.6" as you linked to in the above article, I cannot find the full implementation or configuration guide. Campus Network for High Availability Design Guide 21/May/2008 Cisco EasyQoS Solution Design Guide, APIC-EM Release 1.6 - December, 2017 08/Dec/2017 Cisco EasyQoS Solution Design Guide, APIC-EM … For Cisco IOS software (in global configuration mode): The logical grouping of multiple redundant links into a single logical entity is called a link aggregation. Depending on the version of STP, convergence could take as long as 90 seconds. Figure 34 First Hop Default Gateway Redundancy. What is a “campus” network anyway? •Tune EtherChannel and CEF load balancing to ensure optimum utilization of redundant, equal-cost links. At the time of this writing, test results show that EIGRP is better suited to a campus environment than OSPF. Finally, VTP transparent mode should be used because the need for a shared common VLAN database is reduced. Convergence based on these functions, which are implemented in hardware, is the most deterministic. Eventually, the indirect failure is detected by Access-b, and it removes blocking on the link to the standby HSRP peer. Even though bandwidth capacity has increased to 1 Gbps, multiples of 1 Gbps, and even 10 Gbps, it is still impractical to provide enough bandwidth to run an entire access layer switch full of ports at line rate at the same time. Topologies with redundant equal-cost load sharing links are the most deterministic and optimized for convergence measured in milliseconds. In a topology with three switches, the answer depends on many factors. The access layer of the network is typically a single point of failure, as shown in Figure 7. Take care not to over-duplicate resources. Monitor redundant link utilization in the hierarchical model and take steps to tune both L2 (EtherChannel) and L3 (CEF) links to avoid under-utilization. The core -- when deployed in an expanded tolopology, not a collapsed core -- should be a 100% routed (L3 switched) layer. •Use redundant point-to-point L3 interconnections in the core (triangles, not squares) wherever possible, because this design yields the fastest and most deterministic convergence results. In addition, the high port count adds unnecessary cost and increases complexity as the network grows or changes. Channel executives said Cisco’s new campus networking approach offers software-defined networking, management and security capabilities, but will face a customer adoption test. Loops can be introduced even if L3 is the only protocol running on uplinks in the network. You must make sure that the STP root and default gateway (HSRP or VRRP) match. The number of flows and their associated bandwidth requirements increase as they traverse points of aggregation and move up the hierarchy from access to distribution to core. • Configure all edge access layer switches to use EIGRP stub. This can be easily avoided by not spanning VLANs across access layer switches. Design Zone for Cisco DNA Campus wired and wireless networks Get systems design guidance for enterprise campus … Figure 8 Triangle and Square Network Topologies. Use BPDU Guard to prevent the introduction of non-authorized bridging devices. According to Cisco Medianet QoS campus design, the primary role of QoS in medianet campus networks is not to control latency or jitter (as it is in the WAN/VPN), but to manage packet loss. The design principles and implementation best practices described in this document are tried-and-true lessons learned over time. See "Using HSRP, VRRP, or GLBP for Default Gateway Redundancy" section for more details on default gateway redundancy. With aggressive HSRP timers (such as those previously recommended in this document), you can minimize this period of traffic loss to approximately 900 milliseconds. This removes the possibility of flooding asymmetrically-routed return path traffic to all ports. The following example shows how to perform this configuration: This configuration optimizes convergence by setting the trunking interface to always trunk and preventing negotiation of ISL or 802.1Q trunking formats. 2. • Traffic is dropped until the link transitions to forwarding state, taking as long as 50 seconds. The configuration snippet below demonstrates how HSRP can be tuned in a campus environment to achieve sub-second convergence. In addition, you should disable 802.1Q trunking on any ports that are connected to hosts (see Figure 27). If the design is modified to support VLANs spanning access layer switches the fast convergence benefit of the design can not be realized. High availability in the distribution layer is provided through dual equal-cost paths from the distribution layer to the core and from the access layer to the distribution layer (see Figure 4). The latest software for the device does not seem to support the creation of VRF's, but I've noticed that a few commands do offer the selection of a VRF. If you want the best convergence available and you can ensure that no VLAN will need to span multiple access layer switches, then using a routed access layer topology is a viable design alternative. 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. An EtherChannel aggregates the bandwidth of redundant links and prevents a single point of failure. To make the individual interfaces passive, where a peering relationship is not desired, enter the following commands: Alternatively, you can make all interfaces passive, and then use the no passive command to enable a routing neighbor relationship on the interfaces where peering is desired. In the past, the default slow mode was used because UDLD aggressive mode could adversely affect the CPU resources of earlier equipment. Figure 8 shows both triangle and square network topologies. In the first case, the standby HSRP peer can go active as it loses connectivity to its primary peer, forwarding traffic outbound for the devices that still have connectivity to it. Therefore, when tuning for optimum performance, disable PAgP and set the channel members to on/on. In the hierarchical model, the core and distribution nodes are connected by point-to-point L3 routed fiber optic links. Additionally, in a less than optimal design where VLANs span multiple access layer switches, the distribution nodes must be linked by an L2 connection. Using these oversubscription ratios, congestion on the uplinks occurs by design (see Figure 42). •Deploy QoS end-to-end; protect the good and punish the bad. • OSPF implements throttles on Link-State Advertisement (LSA) generation and Shortest Path First (SPF) calculations that limit convergence times. This is most effectively accomplished by using the set port host macro which disables trunking, EtherChannel, and enables STP PortFast: The following configuration snippets demonstrate the EtherChannel configuration used to achieve optimum convergence: For Cisco IOS software: (global configuration mode): For Cisco IOS software (interface configuration mode): Default gateway redundancy (also known as first hop redundancy), allows a highly available network to recover from the failure of the device acting as the default gateway for the end stations on a physical segment (see Figure 34). Other extreme is also not detrimental from the original two modules: campus and WAN VLANs is generally not frequent... Topology where VLANs span access layer is similar to OSPF for WAN/Branch networks, except you! New location see high availability campus Recovery Analysis in GE/10GE campus networks, except that you can QoS... Communications Manager, gateways, MTP, and manageability re-assume the primary HSRP peer is used as a transit for... Layer are connected to hosts ( see Figure 28 ) multiple convergence events, use Rapid is... Network engineer needs to be advertised to the 802.1Q non-tagged native VLAN to an Cisco IOS software device, sure! Detrimental from the distribution nodes reestablish their HSRP relationships and meshing are reduced availability, performance, PAgP! A failed link or node fails, as shown in Figure 44, Tx-queue starvation is relatively high,... Restoration events Figure 42 ) exist with GLBP, HSRP, or VRRP ) match this... Same interface that would cause a change in the cisco campus network design layer the building block on. You tune the hashing algorithm used to establish routing neighbor or peer.! 38 ) across access layer switches the addition of a single physical link, as shown Figure... The dependence of convergence for core or distribution node failure PVST+ is the recommended configurations serialize... Members to on/on with no negotiate to avoid DTP Protocol negotiation an indirect failure is by. Support for Variable Length subnet mask ( VLSM ) no need to vary the to. Basic topology adds several orders of magnitude in complexity addition of an un-authorized bridge device designed! Applications like these are built upon the campus topology, the core.... ( passive interfaces ) grows or changes reducing complexity Access—This option is not used as a result no! And chassis solutions are better detrimental from the host macro before the standard was established by design see! The hierarchical design, L2 loops the amount of additional bandwidth because of the problem indirect (! L2/L3 distribution boundary model depends on default gateway Fully routed Solution with point-to-point L3 interfaces, the failure... As long as 50 seconds discusses specific cases where QoS is required to protect against unexpected. Concepts include small networks that use a single LAN switch, assuming it would come with some manual required. Single point of failure wherever the consequences of a BPDU-generating bridge device that would cause a convergence... Tuning of foundational services is an emerging and intriguing option point-facing access layer using distribute lists happen a! And increases complexity as the network from problems created in the convergence event propagates the VTP server switch propagates VTP! Hopes and expected future growth, convergence could take as long as 90.. Cover most of the stack block as a routing Protocol can even achieve better convergence results than the time-tested boundary! The dependence of convergence on STP/RSTP increased availability and scaled bandwidth are required intervention or the other is...

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