How to Improve Network Speed with a LAN Switch

When the traffic load grows on your network, how do you steer around congestion and reduce collisions to improve network speed? By switching.


"Network switches are like the tires of a car—you take them for granted until there's a problem," says ITPointe President Gabriel Ruiz. "Then everybody relying on them suffers."

Effective switching is essential to handle the growing network traffic coming from video and other bandwidth-intensive applications, more user devices, and more packets headed to servers and storage in the cloud.

"When you begin a cloud service, don't be surprised to see that you're pushing out 50 percent more traffic to the Internet than you had before," says Ash Creek Enterprises President Mark Calzone. "Your network infrastructure must be ready."

Any small or midsized business can use LAN switching to sustain the speeds and availability that users need. This article presents five ways to do it, from experts at two Cisco® Certified Partners that do it every day.

ITPointe, a Cisco Premier Certified Partner, provides unified communications, videoconferencing, virtualization, and other network solutions, with an emphasis on advanced on-staff engineering expertise, solutions that are on time and within budget, and strong support.

Ash Creek Enterprises, a Cisco Premier Certified Partner, specializes in network and server integration, with ongoing service that emphasizes business best practices, helping IT staff use technology proactively, and long-term consultative relationships.

Step-by-Step Guide to Improved Network Speed

1. Segment Your Network Logically, Using VLANs

A traditional flat network (which places all traffic in a single broadcast domain) can easily overload switch links. Instead, apply your switch's VLAN features to send traffic only where it needs to go, at the speed it needs to go.

"Collisions are inevitable," says Joe Cichowski, technical sales director at Ash Creek. "Your objective for each segment is a collision rate of less than 10 percent."

You can use a variety of Layer 2 and Layer 3 VLAN types to segment traffic. Many Cisco switches for small and midsized businesses offer all of the following types of VLANs:

  • Protocol, such as a VLAN dedicated to IP voice or video traffic
  • Devices, such as a VLAN for wireless clients, a server or printer, or all the equipment on a building floor
  • Port, such as a VLAN for a department or other group of users
  • Guest, MAC address, and unauthenticated traffic
  • Dynamic VLAN assignment that uses the end device's source MAC address to assign switch ports to VLANs
  • Multicast VLAN Registration (MVR), which organizes multicast traffic into a dedicated VLAN while maintaining the users' other VLANs. Internet Group Management Protocol (IGMP) Snooping limits the traffic to the devices that need it.

2. Provide the Needed Capacity

Deploy the processing power and bandwidth that your segments, applications, and users need. To reduce latency, congestion, and collisions, apply switch capacity capabilities such as:

  • A fast engine: Nonblocking wire-speed silicon chips. Switches that forward traffic at wire speed sometimes cost more "but can be the performance difference you'd see between an old and new car," says Cichowski. For example, tests by Miercom show that Cisco switches (all of which use nonblocking chips) forward with zero packet loss.
  • Link Aggregation Control Protocol (LACP). This standard feature increases available bandwidth by trunking ports. "Think of using LACP on four ports as dynamically adding four traffic lanes, not increasing speed fourfold," says Ruiz.
  • Gigabit bandwidth on LAN ports and uplinks. "It took a long time for links to go from 10/100 Mbps to 1 Gbps, but small and mid-sized businesses are now quickly moving to 10 Gbps, and soon it will be more," says Calzone. "We recommend you review your infrastructure annually, and pace your CapEx by planning a five-year lifecycle."
  • Stack'em."If you can, stack your switches to increase throughput and have them operate as one device with a single IP address," says Ruiz. "The throughput of a stack of Cisco Catalyst 3750-X Series Switches can be up to 64 Gbps."

3. Apply Wire-Speed Routing Between VLANs

Inter-VLAN routing is necessary for any user or server that uses multiple VLANs.

"Use your switch, not your router software, to route inter-VLAN traffic," says Ruiz. A switch's hardware can do the routing, at wire speed. And offloading the router allows it to better handle its WAN connectivity and firewall functions, improving overall network performance.

"Absolutely take advantage of both the static and dynamic IP routing capabilities in your switch," says Cichowski.

4. Prioritize Applications and Apply Traffic Shaping

"Make the best use of your bandwidth by controlling access to it," says Cichowski.

You can use the following switch features to set performance parameters based on the traffic's importance and sensitivity to jitter and latency; also check to confirm that the connected devices support the feature:

  • Prioritize applications by 802.1p/q tag (a Layer 2 switching capability)
  • Prioritize applications by IP header (differentiated services code point (DSCP)/type of service (ToS), a Layer 3 switching capability).
  • Shape traffic to delay packets, using criteria such as bandwidth throttling or rate limiting.

5. Set Endpoint Parameters, Preferably Automatically

Set the switch's endpoint ports for optimal performance, using parameters such as storm control, number of devices allowed, quality of service (QoS), and VLANs.

A switch with "smart ports" can detect new devices and use macros to configure many port parameters accordingly. "Having automated QoS settings for IP phones and other devices really helps speed configuration, and you can always adjust the default settings," says Ruiz.

"Cisco switches can also connect endpoints using what I call 'the Facebook for network devices'--the Cisco Discovery Protocol," says Cichowski. "It recognizes Cisco devices and pulls the data relevant for optimal performance connections, fast problem solving, and efficient network management."

Integrate Your Switching, Reduce Expenses

Applying these five tips--in combination with Simple Network Management Protocol (SNMP) or other monitoring and management tools as well as switch security features such as dynamic Address Resolution Protocol (ARP) inspection, IP Source Guard, and Dynamic Host Configuration Protocol (DHCP) Snooping to thwart attacks--can produce awesome network performance. And help your company save money. For example, an international distributor invested in all new switches to support its new unified communications system. "But the switches were set in a flat network and had no management capabilities," says Ruiz. "By the time the company engaged ITPointe, their phone system and network were down. They had to replace all their new switches."

When Ash Creek upgraded switches for a 200-employee manufacturer, it saved the company hundreds of thousands of dollars that were being lost to production line shutdowns, which had been caused by network latency.

Move into the Fast Lane

When you need to speed up your network, Cisco Certified Partners can help you make adroit switching and infrastructure moves--including network assessment and design, solution financing and implementation, and onsite support and/or managed services.

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