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I'm starting to learn basic switching / networking and I've hit a small hiccup in understanding a fundamental thing. In the scenario I have a L3 switch (Brocade in my environment) and the facility gave me a /24 (We'll say

Now would you assign the full range to switchport 1? Or would you assign say a /30 to switchport 1 and subnet the remainder depending on your needs (VLAN's, default VLAN, single port)?

The former makes no sense to me as there would be overlapping subnets if you attempted to assign anything within that subnet elsewhere.

What's the proper procedure for this?

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Before we answer your question, would you return the favour by marking your old questions as answered? 12% is really quite low. – Jay Oct 11 '12 at 22:18
I went through and answered what I feel should have been. Most of them I answered myself and never updated. – WinkyWolly Oct 11 '12 at 22:27
Thank you - if you found the answer and it's not one of the posted ones, please just post it and accept it, we encourage that too. – Jay Oct 11 '12 at 22:28
What do you mean by "to switchport 1"? You assign IP addresses to networks, not ports. By "switchport 1" do you mean the link to the facility? – David Schwartz Oct 11 '12 at 23:28
You configure that port according to the information given to you by the facility. (Is there a /30 for the link between you and the facility that other subnets are routed over? Is the subnet bridged to you? Did the facility ask you how you wanted it? Usually, they will ask you what kind of device you're going to connect and configure their end appropriately and, of course, share that configuration with you.) – David Schwartz Oct 11 '12 at 23:44
up vote 1 down vote accepted

Generally, it depends on the arrangement with the facility. Often you will be asked how you want the traffic exchanged. A typical question will be something like: "Are you planning to connect an L2 device or an L3 device?"

If the provider expects you to connect an L2 device, then the whole network will usually be bridged to you. You'll be given a gateway IP inside that subnet that should be the default gateway for your devices. This makes it difficult to subnet, but you don't need any routing equipment at all if you don't want to use it.

If the provider expects you to connect an L3 device, then there will usually be a small network (like a /30 or /29) that it outside the network they are routing to you. You'll be given an IP address for your end of that small network and they'll have an IP inside that network for their end. You then configure the link to them for that small subnet. They route all traffic to your main network to your side of the small subnet. You route all traffic for your provider to their side of that small subnet. This lets you subnet your main network however you please.

Most providers will first send you a sheet with specific questions about how you want the connection set up. After the provision it, they should give you a sheet with the specifics about how the link was provisioned to allow you to easily set up their end. (And to avoid having every single customer asking them the same 50 questions.)

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Alright, the facility I'm working with only gave me a single /24. I was under the assumption I was to get another small range (/30 at least for the switch itself). So to clarify I'd get a small range (/29 or /30) and assign it to the switch. From there they'd route the larger ranges (/24, etc) and I could subnet / route those however I please? – WinkyWolly Oct 12 '12 at 0:16
That's the usual setup when the facility knows that you'll be connecting with an L3 device. You route traffic for them to their IP inside the /30, they route traffic for you to your IP inside the /30. – David Schwartz Oct 12 '12 at 0:22
Absolutely perfect. Thank you for your explanation :). – WinkyWolly Oct 12 '12 at 0:29

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