Squeezing Bandwidth & Value From 2924XL's

[mmcgurty]

We have about 30 or more Cisco 2924XL's in our company. Most of them are setup pretty standard, are there anythings I could do to yield better performance or bandwidth from them? I am looking for really easy ways to help out the PC's and other devices connected with major changes that would take down the users (24x7 operation).

Thanks!

 

[wybnormal]

I hate to ask but have you run any baselines yet to find out where the bottlenecks are.. if there are any? Most times I have been called about lack of bandwidth, it normally comes down to something else.. not so much raw bandwidth. Cleaning up all unused protocols, prune the broadcasts as much as possible come to mind.. make sure all uplink ports are full duplex.. gig on the uplink if you can do it or etherchannel two ports to get 400Mbps of uplink.. Dont daisychain the switches by the 10/100 ports.. bad idea since the last switch has to pass aggregate traffic from all those in front of it.. hence the need for the uplink ports..

MikeS "Diplomacy; the art of saying 'nice doggie' till you can find a rock" Wynn Catlin

 

[mmcgurty]

We know where the bottlenecks are, specifically we run mostly CAT3 in the building which works, but seems to intensify problems with cabling. Nothing can be done about this at the time. All the workstations come from old Synoptics 3000 or 5000 hubs. Of course, in a network like this there are hubs hanging from the Synoptics also, violating ethernet laws. To do it all right, it would cost in the neighborhood of $100,000, which the company is unwilling to spend at this time.

As far as the protocols, we run very little. IP and IPX in some, IP, IPX, and DECnet in others. It mostly IP and IPX traffic. We can't run all ports full duplex since almost everything that isn't in the same room is on a hub. We connect all of the servers to the switches as 100/full duplex. However, I have never heard about this Etherchannel. Do you need a router to do this? I am sure some of the servers could benefit from this. Also, we do daisychain the switches by using a crossover cable. Is this a bad idea? I don't understand why it would be a problem. Should we be buying switches that have fiber or gigabit ports (Cisco 2922XL-M)?

I appreciate the reply...gives me a lot to look at but little I can do without the money.

 

[wybnormal]

Etherchannel is something you can do for "free" assuming you have the extra ports to use. It's a poor mans "gig" backbone ;-) Myself, I would get the switches with the gig backbone IF you have the option.;but.. if not.. then read this :

http://www.cisco.com/univercd/cc/td/doc/product/lan/c2900xl/29_35xu/scg/kiconfig.htm#xtocid5747

Search the text on etherchannel

THis one is just for the 2900 series..

http://www.cisco.com/warp/public/473/44.html

You need to know how much traffic there is on the chain..

switch1----switch2----switch3= total

Add the total traffic from switch 1 and 2 to see what 3 has to pass along with ITS own traffic. This is where you get into trouble with the daisy chain.

One idea is to

hub----------S
hub----------w
hub----------i
hub----------t
hub----------c
hub----------h

This breaks up the collision domains on the hubs. It can also give you some control by using vlans on the 2900s and a 2621 router as the "router on a stick"

Put CAT5 in place or Fiber for at least the backbone connections. A few cheap (??) routers could help alot by breaking up the broadcast domains and using access lists to control what broadcasts you do need to pass back and forth.. vlans do the same but they might be more difficult to setup. For example.. IPX is very..very noisy on the network with all the SAP traffic. Check and see if there is any Netbuei on the wire.. get if off if you can.

MikeS


"Diplomacy; the art of saying 'nice doggie' till you can find a rock" Wynn Catlin

 

[mmcgurty]

Some of our switches have open ports, others do not. The places we need it on for sure do not. Since they like to "keep it simple" they will only purchase 2924XL's. This is to keep from getting devices that we do not have spares for.

How can I check how much traffic is being generated on that chain? Any utilities (Solarwinds) that does this? We could probably do the VLANS if someone knew the correct way to do it and could implement it without much downtime or changes to users. In fact, VLANS is something I have suggested for a long time. The things you showed about the hubs wouldn't work. Let me explain.

12 floors in the building, 300-400 users spread throughout. Floor 2 contains the networking equipment, racks, servers, punch downs, and PBX. On floors, 5-7-9-11 there are Synoptics hubs with at least 5 CAT5 or coax cards in them which run on a single cable back to either Floor 2 or the closest Synoptics which will run back (to stay within cabling length specs). However, almost all PC's go to a 66 punchdown block which goes to Floor 2 where they are punched down again to an octopus cable into a Synoptics which runs to a switch. It really is a mess that CAT5 or Fiber backbones would do a lot to help, but its a money factor. No one seems to think this idea is worth while, that the system will run (limping) the way it is.

No NetBUI whatsoever...just IP and IPX in this particular building.

 

[Guntha]

I was just reading this thread and was hoping someone could explain to me why a crossover cable is needed in linking switches? I have a 3524 with two Fiber optic GIG uplinks that go to other 3524 switches. I also run regular CAT 5 cable with 568B wiring to a couple D-link switches (read no crossover cable) everything seems to be fine, granted there are not alot of users on the D-Link switches, that's why we went with D-Link instead of more CISCO switches. What am I missing here? Sorry to jump on someone elses thread.

Thanks!!

 

[wybnormal]

A crossover is just flipping the transmit and receive pairs. Many switches will do this either by a switch or automatic. Some do not depending on a vendor. It's safe to *assume* that switch to switch needs a crossover cable unless wise shown that you dont.

You gig uplinks do roughly the same thing as there are two fibers used.. one is Tx and the other Rx. They either flip at the other end or the equipment flips them for you. More then likely since it's fiber, you do the flip.. Tx to Rx and Rx to Tx.

MikeS
"Diplomacy; the art of saying 'nice doggie' till you can find a rock" Wynn Catlin