Subject: Switches Vs Routers and EGP vs IPG

From: Betsy Brennan <[email-masked]>
Date: Fri, 24 Mar 2000 13:47:57 -0500

Can you help me understand when a router would be used instead of a
switch?   

Also, I need to understand the differences between EGP and IGP.
I know that IGP is for exchanging network info within a network
and EGP is for use between Autonomous systems, but what other
differences are there?
Respectfully, Betsy B.

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From: "Baghdad Barka" <[email-masked]>
Date: Fri, 24 Mar 2000 14:35:32 -0500

> and EGP is for use between Autonomous systems, but what other

To Betsy Brennan:

Historically,The use of routers in existing LAN infrastructures has
led the adoption of IP addressing schemes in which multiple IP subnets
exist within the LAN. Packets can only be forwarded between subnets by 
a routing function (Router capabilities), not by LAN switches.

Replacing routers by switches would require that the IP addresses of 
all the stations on the LAN be changed so that all the addresses are on
a single subnet identity, which is not a good approche .............

Unlike switches, most routers offer a range of access controls which 
can form a useful part of the entreprise LAN security policy.

A fully switches LAN which has no routing in it would have to operate
as a single large broadcast domain.

In the other hand switch reduces shared media contention ....

And we do have MLS " multilayer switch" that combines the performance
of switching with the intelligence of routing. There are several 
different approches to "Multilayer Switch" from
   - Cut-Thru Layer 2 "CTL2"
   - Packet-by-Packet Layer 3 "PPL3" 
   - and even some Layer 4 solutions. 

Switching at Layer 3 is actually routing ..

I hope that will help you Betsy to make a diffrence between 
router and switch ....

Baghdad Barka