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Cisco Systems manual Components Used, Background Theory, IP Routing on a Stack of 3750s

Models: 3750

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Components Used

The information in this document is based on the software and hardware versions below.

∙Two Catalyst 3750G−24T switches running 12.1(14)EA1 EMI Software Release stacked together

∙Catalyst 2950G−48 running 12.1(12c)EA1 EI Software Release

∙Catalyst 2948G running 6.3(10) Software Release

Note: The configuration from the Cisco 7200VXR is not relevant and, therefore, is not shown in this document.

The information presented in this document was created from devices in a specific lab environment. All of the devices used in this document started with a cleared (default) configuration. If you are working in a live network, ensure that you understand the potential impact of any command before using it.

Background Theory

In a switched network, VLANs separate devices into different collision domains and Layer 3 (L3) subnets. Devices within a VLAN can communicate with one another without requiring routing. On the contrary, devices in separate VLANs require a routing device to communicate with one another.

L2 only switches require a L3 routing device (either external to the switch or in another module on the same chassis). A new breed of switches, however, (for example, 3550 and 3750) incorporate routing capability within the switch. The switch receives a packet, determines that it belongs to another VLAN, and sends the packet to the appropriate port on the other VLAN.

A typical network design segments the network based on the group or function the device belongs to. For example, the engineering department VLAN would only have devices associated with the engineering department, while the finance VLAN would only have finance related devices. If routing is enabled, the devices in each VLAN can talk to one another without all the devices being in the same broadcast domain. Such a VLAN design also has the added benefit of allowing the administrator to restrict communication between VLANs using access−lists. In our example, the engineering VLAN could be restricted (using access−lists) from accessing devices on the finance VLAN.

IP Routing on a Stack of 3750s

On a stack of Catalyst 3750 switches, the software running on the master determines the capabilities of the whole stack. If the master switch is running an EMI image, the whole stack will support the full set of supported routing protocols (such as Open Shortest Path First (OSPF), Enhanced Interior Gateway Routing Protocol (EIGRP), and such) even if the other stack members are just running an SMI image. However, it is advisable to have the same software running on the different stack members. If the stack master fails, you would lose the extended routing capabilities if the other members run an SMI image as opposed to the EMI image of the former master.

A stack of Catalyst 3750 switches appears to the network as a single router, independent to which of the stack switches the routing peer is connected. A router will create a single adjacency with a stack of 3750 routers.

The stack master performs the following tasks:

∙Initialization and configuration of the routing protocols

∙Generation of routing protocol messages

∙Processing of received routing protocol messages

Cisco − Configuring Inter−VLAN Routing with Catalyst 3750 Series Switches in a Stacked Configuration

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Cisco Systems manual Components Used, Background Theory, IP Routing on a Stack of 3750s
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3750 specifications

The Cisco Systems 3750 series is a family of enterprise-class stackable switches that were designed to provide high-performance networking solutions for organizations requiring robust management features, security, and scalability. Known for their reliability and advanced capabilities, the 3750 series is particularly aimed at accommodating the demands of LAN environments in organizations ranging from small businesses to large enterprises.

One of the defining features of the Cisco 3750 series is its StackWise technology. This innovative feature enables the stacking of up to nine switches together, allowing them to function as a single logical unit. This results in simplified management, higher redundancy, and increased scalability. The StackWise technology allows for seamless failover and enhanced bandwidth between the stacked switches.

In terms of performance, the 3750 series supports Layer 2 and Layer 3 switching, offering routing capabilities to handle both traditional and modern network demands. It is equipped with advanced Quality of Service (QoS) features, ensuring that critical applications such as voice and video are prioritized for optimal performance.

The Cisco 3750 also features extensive security capabilities. It incorporates features such as IEEE 802.1X authentication, DHCP snooping, and dynamic ARP inspection to protect against unauthorized access and various network attacks. These enhancements help maintain data integrity and secure communications across the network.

Another noteworthy characteristic of the 3750 series is its support for Power over Ethernet (PoE). PoE allows for the delivery of power over Ethernet cables to connected devices, such as IP phones and wireless access points, facilitating simpler installations and reducing the need for additional power outlets.

The Cisco 3750 series also provides a comprehensive set of management tools. With features like Cisco's Embedded Event Manager (EEM) and extensive SNMP support, network administrators can efficiently monitor and manage network performance, troubleshoot issues, and maintain high availability.

Additionally, the series is compatible with Cisco's IOS software, which provides a rich set of features, including advanced routing protocols, multicast support, and extensive security options, further enhancing the functionality and versatility of the switches.

Overall, the Cisco Systems 3750 series stands out for its stackable design, high-performance features, security capabilities, and management tools, making it a popular choice for organizations looking for dependable and scalable networking solutions.