jk's blog

A Small Large Network: USG-50, GS108T, HP 1910

The networking workbench.

This is a set of posts about building a small large-network. They are notes I’m taking as I’m learning about the router and its use in a network with simple VLAN and routing requirements. So they will change, and eventually will make more sense than they do today.

The study is being done with the following equipment: USG-50, Netgear GS108T switch, and a HP 1910 48 port switch. I may also include notes regarding some older Cisco switches. This is for a small network that is going to use some large-network features.

There’s a lot of good study material online, especially at Small Net Builder.

Intro: What is a small large-network?

That’s the term I’m using to describe a small network that has some large-network features, like VLANs, static routing, redundancy, and caching. I’m not a small biz net consultant, so I don’t have a sense of the range of needs of the current small biz, but I do admin a network that fluctuates between a dozen and over 100 active nodes. As cloud computing and the overall scale of data increases, and the amount of data being written increases, systems and networks invariably become more complex.

Yet, at the same time, the consumer market has produced easier-to-use products, at a lower price, and with much quicker obsolesence than in the past. The consumer market is dominated by plug-and-play networking. When the number of plug-and-play devices goes from single digits to double and triple digits, “plug and play” stops working so well.

You end up with too much broadcast traffic, with every smartphone sending broadcast packets looking for printers, and every PC trying to discover the other PCs. You also create security problems when a bunch of plug-and-play devices are on the same LAN as a bunch of telephone call stations, the accounting network, and the office network. Who brought in the PC with the virus that knocked out one of the network services? Nobody knows, because their meeting ended half an hour ago, and they left.

Cloud services used to be only websites, but now they span everything from telephone calls to file servers. These have divergent requirements – low packet latency for phone calls, and extremely large bandwith hogging streams for file servers. Finicky VPNs seem to require good connections.

Design Concept

The tools I’m going to use to build the network are managed switches and a router. The router is an all-in-one device that includes a small switch that can do VLANs.

The basic design is to separate the LAN into VLANs, and route between them with the router. This will allow me to treat each VLAN differently.

There are three main VLANs. The office, the phone center, and the guest network. This design differs from most new LANs in that we don’t have a voice network for the office. We are still using a traditional style PBX that runs on two wires, mainly because we had all that wire in the walls, and our computer network was wired with CAT5, not CAT5e or CAT6, so it might not run at 1Gbps. Voice network features will be implemented in the phone center – but again, this scenario differs from the typical because we don’t have “hard phones” or standalone SIP phones. We use a software phone.

Depending on the schedule, the guest and office LANs will have their bandwidth limited. At night, for example, bandwidth will be throttled so we reduce the chance of exceeding our contract. (We’re paying on the 95th%ile.)

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