Access layer to Distribution layer connection and thoroughput

Chitownjedi

Hey guys,

Currently studying for ICND2...

This is not a question that seems as if it will be covered this is more of... when I get into something I start wondering about how it works so here is my question...

You have access layer switches with end users between 250-500 users... and they feed up to distribution layer switches... Now these switches usually have a faster or should have a faster packet forwarding capability correct? Since they are processing all of the information from the access layer switches and possibly forwarding them up to a core switch.. how does one eliminate bottlenecks? Do they put the links between access layer switches and distribution layer switches into etherchannels? Or do link aggregation? Just wondering how does one combat having multiple access layer switch with tons of information and users flooding the distro level capabilities to the point of slow/failure....

networker050184

You can do etherchannel yes. Most access switches aren't going to be maxing out their bandwidth though. If they are then something is probably broken!

When you design a network you have multiple options. The expensive option is to go full out and ensure that even if all devices send at max throughput at the same time the network can still handle it. This is an expensive option and not usually implemented. Especially when it comes to internet bandwidth at the edge.

The more common option is the over subscribed model. In this model you realize that not every device (or access layer switch) is going to be using all of its bandwidth at all times. For example you have 46 gig ports on an access layer switch yet you only have a two gig etherchannel going up to the access. It's a pretty safe assumption that at any given time you will not have more than 2 gigs coming from this single access switch to the distribution layer. Same with distribution up. You may have 20 x 2 gig etherchannels from access switches and a single 10 gig up to the core.

Chitownjedi

networker050184 wrote: »

You can do etherchannel yes. Most access switches aren't going to be maxing out their bandwidth though. If they are then something is probably broken!

When you design a network you have multiple options. The expensive option is to go full out and ensure that even if all devices send at max throughput at the same time the network can still handle it. This is an expensive option and not usually implemented. Especially when it comes to internet bandwidth at the edge.

The more common option is the over subscribed model. In this model you realize that not every device (or access layer switch) is going to be using all of its bandwidth at all times. For example you have 46 gig ports on an access layer switch yet you only have a two gig etherchannel going up to the access. It's a pretty safe assumption that at any given time you will not have more than 2 gigs coming from this single access switch to the distribution layer. Same with distribution up. You may have 20 x 2 gig etherchannels from access switches and a single 10 gig up to the core.

Thanks for the information helps my understanding tremendously.

sratakhin

You can either use 10 gbit links (very expensive!) or just use something like Etherchannel \ Link Aggregation.