Solved: Links

londint · ‎03-27-2003

I need to link 2 sites and I was wondering which is the better option. We have a 1GB link fiber.

1. Conecting the sites using routers or

2. Connecting the sites using switches. We have L3 switches 1 x6509 and 1 x 3550..

What is the advantage or disadvantage of one over the other.

Also, what is the best termination of the fiber link. How should it be brought into our switches?

Thanks for your help.

konigl · ‎03-27-2003

Connecting your two L3 switches together over fiber is infinitely preferable to using routers with fiber. It all comes down to the need for speed, the availability of fiber infrastructure, and the ability to afford the cost. I work for a dark fiber construction company. If a customer needs link speeds 4 megabits per second or greater, and they're within our service area, we can usually provide them with a switched fiber solution that runs faster, is easier to maintain, AND is less expensive than what they would pay the telcos for a routed T1, NxT1, FT3, or T3 leased line solution.

Hardware-based L3 switching in your 6509 supervisor module's MSFC(2) and PFC(2) is "wire speed" for IP and IPX traffic; versus software-based routing in a router, which tends to bottleneck performance at the higher interface speeds. The L3 switch's performance is an order of magnitude (or two or three, depending on which model you compare it to) faster than a router's. Switch when you can, route when you must.

Your WS-X6416-GE-MT is sixteen ports of SX-type Gigabit Ethernet optical signaling, pushed through MT-RJ physical interfaces. These ports are meant to be connected to multimode fiber (MMF); and as such, will be subject to a supported transmission radius of 220 to 275 meters from the 6509, depending on the type of MMF used.

Unless your two sites are within this distance, you should be thinking about single mode fiber (SMF). Your provider is most likely looking at installing SMF, and probably planning to terminate it with SC connectors. This type of fiber is better connected to an LX/LH GBIC or a ZX GBIC, installable in the GBIC slots you have in your 6509's supervisor module, or in GBIC slots in an 8-port or 16-port Gig Ethernet GBIC module. With SMF, you can go up to 10km with LX/LH GBICs; and 70 to 100km with ZX GBICs, depending on the type of SMF used.

If you want or need to terminate the SMF link on available interface ports that are SX or TX and which expect MMF or unshielded twisted pair (UTP) copper, think about using media converters. Transition Networks (www.transition.com) is one company with a wide selection of these; there are others. And if you need to connect an MMF MT-RJ port on that 6416 card to an MMF SC port on a media converter (where the signal is then converted to LX or ZX-type signaling more appropriate for transmission over SMF), you can get patch cables with the appropriate connectors at each end.

Go fiber!

Hope this helps.

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lgijssel · ‎03-27-2003

When you have the opportunity to skip the routers, this is adviseable.

It will save a lot of budget and two points-of-failure. With a Layer3 switch on each side you can realize high performance routing.

Terminating the fiber link can best be done through a fiber patch panel using SC-style connectors. From the patchpanel, you can then patch on to a Fiber GBIC in the switch. Is this your question? It seems rather obvious so I might miss the point here.

Regards,

Leo

londint · ‎03-27-2003

Yes, thanks os much for your help. Yes that is what I wanted. We have WS-X6416-GE-MT which are kind of like GB for servers, are we able to use them for WAN links?

Actually what I wanted to know is what is the best termination the provider should bring the link on.

Thanks

konigl · ‎03-27-2003

Connecting your two L3 switches together over fiber is infinitely preferable to using routers with fiber. It all comes down to the need for speed, the availability of fiber infrastructure, and the ability to afford the cost. I work for a dark fiber construction company. If a customer needs link speeds 4 megabits per second or greater, and they're within our service area, we can usually provide them with a switched fiber solution that runs faster, is easier to maintain, AND is less expensive than what they would pay the telcos for a routed T1, NxT1, FT3, or T3 leased line solution.

Hardware-based L3 switching in your 6509 supervisor module's MSFC(2) and PFC(2) is "wire speed" for IP and IPX traffic; versus software-based routing in a router, which tends to bottleneck performance at the higher interface speeds. The L3 switch's performance is an order of magnitude (or two or three, depending on which model you compare it to) faster than a router's. Switch when you can, route when you must.

Your WS-X6416-GE-MT is sixteen ports of SX-type Gigabit Ethernet optical signaling, pushed through MT-RJ physical interfaces. These ports are meant to be connected to multimode fiber (MMF); and as such, will be subject to a supported transmission radius of 220 to 275 meters from the 6509, depending on the type of MMF used.

Unless your two sites are within this distance, you should be thinking about single mode fiber (SMF). Your provider is most likely looking at installing SMF, and probably planning to terminate it with SC connectors. This type of fiber is better connected to an LX/LH GBIC or a ZX GBIC, installable in the GBIC slots you have in your 6509's supervisor module, or in GBIC slots in an 8-port or 16-port Gig Ethernet GBIC module. With SMF, you can go up to 10km with LX/LH GBICs; and 70 to 100km with ZX GBICs, depending on the type of SMF used.

If you want or need to terminate the SMF link on available interface ports that are SX or TX and which expect MMF or unshielded twisted pair (UTP) copper, think about using media converters. Transition Networks (www.transition.com) is one company with a wide selection of these; there are others. And if you need to connect an MMF MT-RJ port on that 6416 card to an MMF SC port on a media converter (where the signal is then converted to LX or ZX-type signaling more appropriate for transmission over SMF), you can get patch cables with the appropriate connectors at each end.

Go fiber!

Hope this helps.

rjackson · ‎03-27-2003

Lets get real here. Connecting them with layer 3 switches is connecting them with routers. Yes they are faster than traditional routers and it is the y way I have my MAN set up, but its function is to block broadcast traffic from the link which is why you would use routers instead of bridges.

konigl · ‎03-27-2003

rjackson,

I agree with you that their main functions are to contain broadcast traffic, and to provide for unicast and multicast forwarding from one broadcast domain to another. In that respect, L3 switches are a lot like traditional routers; if they didn't do that, we would just call them switches, which is easier to say than "wire-speed bridging multiport repeaters".

However, while they perform a lot of the same functions, L3 switches are not the same as routers. That's why they're called something different. It's how they do what they do, that sets them apart.

A 3550-12T L3 switch will blow the doors off any traditional router chassis on steroids configured with 12 GigE interfaces, for a heck of a lot less money -- IF what you're doing is limited to the specific strengths of what a Layer 3 switch can accomplish (i.e. termination of multiple high-speed LAN connections, simplified protocol forwarding requirements such as routing TCP/IP only, with the routing handled in ASIC hardware). And it takes up less space in the rack, too.

It used to be the case that you could distinguish the two types of devices by saying that routers could directly interfaced with non-LAN technologies (think WAN connections like T1 or T3 to your ISP, for example) and L3 switches couldn't. But Cisco has been blurring that line by allowing some chassis switches to take WAN interfaces. In fact, Cisco even has LAN switching modules that can be put into certain routers. So which device you use -- L3 switch or router -- depends on a lot of other factors; and sometimes, you might have to use both.

If you choose to configure and use your L3 switches to perform only routing functions (which I do a lot), then it is easy to think of them as wicked-fast routers. I tell a lot of my customers to think of them in this way, if that's how theirs are being configured, because a lot of them get confused by the concept of VLANs.

But, strictly speaking, they are not the same thing. There are subtle yet very important differences.

Just so we're clear, I'm not looking to start an argument here, I am just trying to help.

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londint · ‎03-28-2003

Thanks you ever so much. Deeply appreciated.

Thanks

konigl · ‎03-28-2003

You're quite welcome.

Keep us posted on how things develop; I'm sure we'd all be interested in your experiences...