LAN Party VLANs and Routers

[Ver17]

I am looking into hosting a 1000+ Person LAN in the distant future using mainly Cisco 5500 Switches. One of my concerns is if I will need to incorperate a Router into the network?

With 1000+ players won't the network overhead of all the TCP/IP broadcasts be heafty? Will I need to use a Router and seperate VLANs to break up the traffic?

I have a Cisco 3640 and could get a Cisco 7200 (non VXR) if its really needed.

 

[vipergg]

Yeah putting 1000 active users on subnet will more than likely cause problems , I would break it up and use a router with fast ether connections .

 

[Ver17]

At what point do you think a router is needed? How many users until you need a router? 250? 500? Less?

 

[JoeBloggssss]

Using a router to perform InterVLAN routing between the VLANs is not going to be ideal, as you will only have a 100MB link to the router probably, and the router will also be passing other traffic, even with a gig link still not good practice. If you are using 5500s they are layer 3 switches, why not perform the intervlan routing on them? For a network this big you dont want a router to be a SPOF.

 

[Ver17]

This clears up why I never see routers at large LANs that use 5500 or 6500 switches! I don't know much about intervlan routing *yet* but at least now I know where to start! Thanks a ton.... something tells me this is the answer I was looking for!

So how many people do you think one VLAN should safely handle? Just off the top of your head. Any guess would be great! Or better yet.... how would I be able to tell if a VLAN was over-populated and needed to be cut up a bit? What kind of patterens or errors would I see? Just plain lag accross the board? Would the switches Supervisor module be working harder than it should?

 

[Cluebird]

A general rule of thumb for networks (VLANs) is about 100 users. However, it all depends on traffic you'll be generating. Ethernet standards say up to 1024 nodes per segment but the performance is erratic at best. Going with a totally switched network (no hubs or repeaters) you can have larger networks but the broadcast domains will be the challenge.

You can sniff your network to see the types of traffic you're dealing with. Check CPU utilization rates since the broadcasts have to be handled off the NIC.

HTH

 

[JoeBloggssss]

I usually VLAN based on organisational structure, it provides abit of security as well. Pacing different departmensts within different VLANs and then only explicitly allowing access to each other with ACLs, expect admins have total control. Not sure of your business, but you don't say want HelpDesk or another department to even ping or communcate in anyway with a management department like payroll, this reduces the event of switched sniffing by arp posining clients etc, does not totally remove it or VLAN jumping but helps.

 

[JoeBloggssss]

By the way, your right most large campus use MLS with high end swiches, haveing access, distribution and core layers, this is a cisco recommendation for redudency and scalability. Search for Cisco Hiarchical Campus Design, dependening on the number of switches you will be using you ma be able to put a better network together that will leverge high levels of performance.

 

[vipergg]

With the 5500's you will need a RSM card to route between the vlans . Then I would set it up for mls , this will give much higher throughput . I think the 5500's have like a 3 gig backplane to handle the traffic .

 

[Cluebird]

VLAN based on organizational structure used to be the best practice with L2 cores. However, carrying end-to-end VLAN information across the core is no longer considered optimal. Current design is to move to layer 3 cores and terminate the VLANS on the Access layer switches. Usually the Access Layer switches will have two VLANs, one for data and one for IP Phone. VTP is not used since no end-to-end VLANs so VTP transparent is recommended. VLAN info is trunked to the Distribution Layer devices which handle InterVLAN routing and move to L3 processing across the core. If budgets allow there is now a strong push to move the entire network to L3 handling and get rid of L2 issues. For the interim, rethinking and eliminating end-to-end VLANs is a first step.

The number one fix a network administrator can implement is implementing a hierarchical addressing scheme.

 

[BuckWeet]

If your 5500 doesn't have a RSM, but if you had a 3600 or 4000 router, you could do MLS routing with it..


BuckWeet