Layer 3 switch or Router


I work for an smaller ISP,today we have an 7204 VXR with NPE-G1 controller but this router will probably not meet our future demands.

We only use Ethernet interfaces, 100, 1000, fiber and copper and we do not use any advanced routing protocols, only static as it is today.

This router is the core for access the internet with 200 mbit/s. Behind it is brodband customers and some servers with internet services.

Can we choose an Layer3 switch (Catalyst 4500) instead of this router or is it neccessary ta have an router ?

What is the main difference between router and switch besides the fact that an router has more interface options and can handle more advanced routing ?

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Loading thread data ... pisze:

If you use only static routing it is good for now. You can look for 4948 switch too. But if you will need BGP in future you will need much advanced router as 7600.

But if you have 7204 VXR with NPE-G1 you can route on it about 400Mb/s and I think enough memory to do BGP, and 45xx or 4948 or even 3750G for routing to your clients.

Router 7204 use processor NPE-G1 for routing with is very universal thing but has limited speed by processor, switches with L3 use ASIC for hardware routing with is faster.


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Note - 7600 is really a Cat 6500 running integrated IOS.

Since it scales to 100's of GigE ports, and can keep them all busy it isnt going to be a bottleneck for you for a long time.

Agreed - 7204 is reasonable router and more flexible than a L3 switch.

If you need more fanout and ports, then put some switches on the "LAN" side of the router.

Note that chassis based switches let you mix and match blades and may be more useful then using stackables. They also support much bigger routing tables and so on, and will tend to be more reliable if you add some resilience (with dual power options for example).

Routers are primarily software driven, so more flexible, but lower performance in Mbps / $.

Switches are designed around hardware driven ASICs, with software to do the complicated bits.

As with most electronics, the original black and white differences are now mostly blurred shades of gray, and the 7204, Cat 4500, 3750 and 6500 are just different sets of tradeoffs between classic switches and software routers.

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The reason for replacing the 7204 is that i suspect that it may not be able to meet our bandwidth demands.

If it is capable to route 400mbps is that the same as 200mbps full duplex ?

We may have use for BGP in the future (e.g loadbalancing) so the platform should be able handle that.


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Hi, I think that you can keep the 7204 and put near it some switches like Cat 3750, Cat 4500. 7204 it's a router and performs better than a L3 switches in routing stuff. In the end everything is about your feature plans. In my ISP experience I've worked a lot with 2848G3, 4500, 3550,

3400 ME and I can say that if you want to have all advantages of a router, then keep the 7204.

Bogdan T.

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All that I've said is ok if you want that router only to forward packets and to apply some routing policies (throug BGP,static or other routing protocol). If you want also traffig-shaping or/and traffic policing on the router then you need a powerfull one. But for traffig- shaping or/and traffic policing you can use also the switches (Cat

3750, Cat 4500 and above).
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xt -

This is the only router in our network, all clients access through other providers network so we dont have to worry about that.

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The only difference between a router and layer 3 switch, is that on the router you can do advanced QoS features such as traffic-shaping and bandwidth limiting. If you don't need these features, a layer 3 switch is the way to go because they can move more packets, and are cheaper.

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Thrill5 pisze:

I think it should handle 400Mb/s full duplex but it will be max of preformance with no margin for DDoS atacks.

You can replace NPE-G1 with G2 it increase this platform.

If you think about BGP and 400Mb/s or more you should think about

7600/6500 with sup 720 3bxl/3cxl it has enough memory for BGP (up to 1 000 000 routes in table). I think that BGP is not for load balancing role. Primary role for BGP is you reliability rating as ISP.
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Hi, L3 switches lacks some futureas (not the basic stuff, of course) in routing section (in the end is a switch and not a router, even if a L3 one) not only in the Qos section. But, I think, that , for what you want, a good L3 switch is enough (if you really want to change the router). As I saw untill now, the clients with BGP, receive only a default route and they advertise few prefixes. So, for something like this and 400 MB of traffic, a 7204 is enough (with that recommend upgrade). A 7600 is more powerfull but you only need something like this if you want something advanced (more prefixes received, some advanced policy routing, and so on). Bogdan Tomoiu

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