Thursday, July 14, 2016

Leave a Comment

Layer 2 vs. Multilayer Switches (CCNP)

Ethernet Switch:-A Device that make forwarding decision based on Layer2 or Mac-address information 

  Remember the Structure of MAC Address
Its 48 bits in length and first portion of mac-address identifies Vendor(That manufacture that device).This Vendor identification called OUI(Organizationally Unique Identifier) and remainder of  24 bits are assigned by Vendor and this help keep all the different network devices in the world unique from one another base on the unique mac address and 

Layer2 switch can use this mac-address information to make forwarding decisions 

                         Switch Populates the mac-address table also called as “CAM TABLE” and it can make forwarding decisions based on destination mac-address. That’s the general theory of Ethernet switch operation

Switch Inspection:- 

Here if we Layer2 Switch if this switch trying to determine at which port it should forward the frame it can inspect multiple things:-

1. Layer2 Forwarding information (information in CAM table)
2. May be we have some “ACL for security” and also “ACL for Qos
So Cisco Switch take those “Security ACL” and “Qos ACL” and some other information and merge that together logically and put that information to table referred to “TCAM Table

Router vs. Switches

Ø         Router have Auxiliary Port
Ø         Switch will not
Ø         Router tend to have more flexibility in interface type
Ø         Many switches only support “Ethernet” connection
Ø         Router might be able to support serial connection like T1,E1 interfaces also might have analog interface(for telephony)
Ø         Some high and catalyst switches have similar set of connection 

Ø Switch uses ASIC that give switches very fast performance 

Layer Structure:-
Ø  Building Access Layer:- End user devices connected to the network in this layer might have L2 or L3 switches and these access layer switches may connect to the switches that reside at the network “building distribution layer”

Ø  Building Distribution Layer:- Probably Layer3 or Router which have multiple connection between switches and we have “red oval” going around the connection that called “etherchannel” 
Ø  Campus backbone: - concern with speed, getting traffic from one building distribution layer switch to other building distribution layer switch. We don’t do much packet manipulation at campus backbone. Some higher level switch cisco catalyst 6500 or other


Post a Comment