VLAN Design Principles for Scalable Networks

November 2004 - Reading time 4 minutes

As enterprise networks grow, scalable VLAN design becomes crucial for maintaining performance, security, and manageability. VLANs allow logical segmentation of networks, enabling better traffic control and policy enforcement.

A best practice is to assign VLANs based on function rather than location. For example, separate VLANs for voice, data, and management simplify QoS policies and improve fault isolation. This approach reduces broadcast domains and improves traffic predictability.

When designing VLANs, it’s essential to minimize Layer 2 boundaries. Spanning VLANs across multiple switches can lead to STP complexity and broadcast flooding. Instead, route between VLANs at Layer 3 to contain traffic efficiently and take advantage of modern high-speed routing hardware.

Access layer switches should use consistent VLAN ID assignments and trunking practices. Standardizing VLAN numbering across sites simplifies deployment and troubleshooting. Documenting VLAN usage and IP subnets ensures alignment with IP addressing plans and future scalability.

For high availability, pair VLAN design with First Hop Redundancy Protocols (FHRP) like HSRP or VRRP. This provides default gateway resiliency and avoids single points of failure in the routing path.

Eduardo Wnorowski is a technology consultant focused on network and infrastructure. He shares practical insights from the field for engineers and architects.

Managing Bandwidth with Policy-Based Routing

July 2004 · 6 min read

As traffic types diversified across campus and branch networks, it became crucial to prioritize and route traffic based on application needs rather than destination alone. In this context, Policy-Based Routing (PBR) emerged as a flexible tool in the Cisco arsenal.

PBR allows us to route packets based on criteria like source address, protocol, or even application-specific tags. This means you could route VoIP traffic via a high-speed link and bulk data via a less expensive path — all without needing to modify the underlying routing protocol decisions.

To implement PBR on a Catalyst or router, we define route-maps and apply them to the incoming interface:

interface FastEthernet0/1
 ip policy route-map QoSPolicy

route-map QoSPolicy permit 10
 match ip address 110
 set ip next-hop 10.1.1.1
  

Access-list 110 could define a class of traffic, such as video conferencing endpoints or Citrix client subnets. The ability to selectively influence routing opens up use cases like bandwidth conservation, WAN cost management, and traffic engineering in the absence of MPLS or SD-WAN.

However, with power comes responsibility. PBR overrides the routing table, so improper design or forgetting route fallback can lead to blackholing. PBR also consumes more CPU, especially at scale, so interface-level testing is essential before deploying in production environments.

At this point in the network evolution, QoS and PBR together began forming the foundation of what we now refer to as intent-based routing strategies — even before SD-WAN brought it to the mainstream.

Eduardo Wnorowski is a technology consultant focused on network and infrastructure. He shares practical insights from the field for engineers and architects.

Citrix MetaFrame XP: Deployment in Mixed Windows Environments

Published: March 2004 · 6 min read

Citrix MetaFrame XP sits at a pivotal point in enterprise remote access evolution. By 2004, it’s already common to see heterogeneous Windows environments with NT 4.0, 2000, and the emerging XP/2003 mix. This makes consistent delivery of applications a significant operational challenge.

I deploy MetaFrame XP in sites where older systems still hold line-of-business roles. Citrix’s architecture adapts well—allowing legacy applications to be published from 2000 servers, while taking advantage of speed and policies available in newer OS builds.

Key success factors in these mixed deployments include:

• Load evaluator policies tailored by OS group
• Publishing apps that redirect user data to centralized shares
• Ensuring ICA client compatibility across versions
• Handling printer redirection and profile hygiene

What surprises most clients is how well MetaFrame XP abstracts the underlying OS differences. As long as Group Policy and permissions are tightly managed, user experience can remain consistent even if some hosts are running older Windows versions.

Another area where I see value is in bandwidth management. ICA protocol tuning—especially in WAN environments—still beats the alternatives in terms of user-perceived performance. Mixed OS environments need this flexibility, and MetaFrame delivers.

When working with hybrid Windows networks, don’t delay virtualization until you have a perfect baseline. MetaFrame XP makes incremental modernization possible—one department, one app at a time.

Eduardo Wnorowski is a technology consultant focused on network and infrastructure. He shares practical insights from the field for engineers and architects.