Picking Out Your Core Switch
If you want to design data center or campus LAN with Cisco products, Cisco has many options for you. So it’s not easy to select the right one according to your actual needs. In this article, we just give you some look on this. Go and find more information for your own special case. (Note: In this article it is gravitated towards having L3 features incorporated as well (not an L2-only implementation).
We take this option of Nexus 5500 here in the beginning anyway. Nexus 5500 (5548P, 5548UP, 5596UP) supports all 4094 VLANs and all the ports are 10G with 1G ability as well. When equipped with L3 forwarding module it has the features that are enough for many situations. 5548 has 32 fixed ports (one module slot for 16-port module) and 5596 has 48 fixed ports (three slots for 16-port modules). With Nexus 5500 you at least know in advance how many ports you can get when you by them (compared to the modular switches that have different port densities in different line cards in different oversubscription levels in different generations).
In Nexus family the important advantage is the FEX selection: remote line cards in top of the rack implementations. That also brings one major limitation: with current software (NX-OS 5.1(3)N1) only 8 FEXes are supported when L3 module is used. If you single-home your FEXes then you can have a total of 16 FEXes with each Nexus 5500 pair (you implement core switches in pairs, right?). When dual-homing the FEXes then the maximum total number is of course 8 because all FEXes are seen by both Nexus 5500.
Nexus 5500 switches only have one supervisor but Cisco still boasts that it supports ISSU (In-Service Software Upgrade). However, ISSU is not supported with L3 module installed. Depending on your environment (and FEXing style [can you say that?]) that may or may not be an important factor for you. When dual-homing everything it may not be so big deal after all.
Also, when comparing Nexus 5500 L3 features with bigger core switches you need to make sure that you know your route and MAC address limitations, as always.
Cisco Catalyst 6500
…Catalyst 6500 is the good old DC and campus core switch. With modern supervisors and line cards it can really kick the frames through the rich services it provides in the same box. Plenty of chassis choices for different installations and requirements, as well as line cards and service modules. Do I need to say more? You can “dual-everything”, use VSS to combine two chassis together and so on. Cat6500 can do almost anything you can imagine. It may not be absolutely the fastest, but hey, if you needed the ultimate raw speed you would have selected Nexus 7000 anyway, you remember? Btw, 160 gigs per slot was announced to be coming for Cat6500 so that gives some picture of the situation.
How about Catalyst 4500? A user said like that: “I don’t know Catalyst 4500 very well in core use. My first experiences from Catalyst 4000 were with a separate 4232-L3-whatever module, and it was horrible to configure (CatOS on the supervisor, IOS on the L3 module, internal GEC trunk between those). And Catalyst 4500 (or should I say 4500E?) is totally different: supervisors worth of 7 or so generations (running IOS or IOS-XE), line cards almost as many generations, different chassis generations, and so on. Current maximum bandwidth per slot seems to be 48 Gbps per slot with Sup7E. The supervisor still does all the forwarding for the line cards. Catalyst 4500 does not provide any separate service modules but it provides a set of IOS features. There are also various chassis sizes. In short: not very exciting option for a LAN core but may work well for you.” Well, what’s your experience about Catalyst 4500? Share with us, please!
The newcomer in Catalyst family is Catalyst 4500-X. They are 1U switches with a small expansion module slot. The base ports (16 or 32) are 1G/10G ports and the expansion module is promised to have 40G ports available later. (But again, your DC is apparently not needing those.) Cat4500-X runs IOS-XE and supports VSS to cluster two switches together. If your access layer is not very wide you could run your core with Cat4500-X.
And then there is more DC-grade stuff:
- Nexus 3000: L2/L3 10G switch but more oriented to low-latency implementations with no special feature requirements
- Catalyst 4948, Catalyst 4900M, and so on: The features are similar to Catalyst 4500 but in smaller box with limited number of interfaces available.
…In fact, we can talk more about the Cisco’s Core Switches. If you have any ideas and experience about the Cisco Core Switches, it’s so excited that you can share them with us.
More about Cisco switches’ topics you can read here: http://blog.router-switch.com/category/reviews/cisco-switches/