Enterprise LAN

802.3 is the IEEE for ethernet  base-T
distance is 100 meters for copper
802.3U  is for 100 Mbps
Base-TX is the CAT 5
Base-T4  is for Cat 3  full duplex is not possible.
base-FX is fiber
Class 1 repeater 1 hop
Class 2 repeater can have a max of 2 hops.

gig is 802.3z  1000 Mbps
802.3ab  is 1000 Mbps over copper CAT cables.

In general 100 meters for cat cables
550  for multimode
Single mode can go 10  40 or 70

SX is multimode
LX is singlemode / multimode
CX  is coax like the antennas cables.

802.3ae  is 10GigE
SR is multimode
LR is multi/single
er is single 40 KM
ZX  is  70
10gbase-t  is 100meters

Etherchannel can bundle links.
So if one fails the other ones still send data.
Links must be same speed, same duplex, same vlan or trunk

The tables in the book are antiquated.

Repeaters - dead , they repeat the signal can't have more than 5 segments 4 repeaters 3 populated.

HUbs are a single broadcast domain , single collision domain . they are dead too.

Bridge is a switch that is using software.  2 or more collision domains

Switch is a bridge that uses hardware chips to forward the data. So more ports and faster.
Each port is a collision domain .  Each Vlan is a broadcast domain.

Routers remove the L2 and add their L2 . they work on layer 2
So each port is a broadcast domain and a collision domain.

repeater + hubs  work on bits.
Bridge + switch   work on frames
L3 switch + router    work on packets

LAN design
Network characteristic  is the application protocol
Infrastructure charactersitics is the L2 L3 switching routing
Environmental characteristics  are the geography and distances.

Peer to peer   messaging
client local   80% is local 20% goes out.
Client  server farms     80% is south to north   20% is internal.
client  to enterprise edge.  like exchange or other public servers in the Internet Edge.

Client to server farms has the highest cost and reliability required.


Best Practices.
Access Layer
Limit Vlan to the Rack.       -so you can layer 3 from the access layer.
use RSTP  as it is better than STP faster times.
Set trunks to ON on  no negotiate.
Prune   unused vlans to minimize the traffic.
use VTP  to sync the vlan database.
Use PortFast and label host ports as access ports.
Consider putting   Layer 3 at the access to improve load balancing and convergence.
Use switchport host   to enable portfast on ports so they go to forwarding quicker.
Use Cisco tools.
1. portfast  skip learning and listening.
2. loop guard b  so the port won't switch to forwarding and create a loop.
3. root guard  to mark that port as one that will not allow a switch there to become root.
4. bpdu guard    to disable the port if someone connects a switch.


Distribution layer
Qos Security filtering  policy and redundant links.
If you use L2  then use HSRP, VRRP, GLBP
Use Layer 3 if you can to improve convergence.
Peer on links that will transit data.
Build triangles and not square.
Try to keep layer 2 vlans in the distribution instead of sending them to core.
summarize routes to offload that from the core.
use VSS  to eliminate STP and HSRP
VSL is the VSS link.


Core layer 
Use layer 3
Use same cost links
Use routing
use triangles.

Each building should have the addresses summarized.

Medium size is two layers  200-1000
Distribution and core are collapsed.

Small
One layer.

Server connect.
Single Link NIC
Single NIC two ports  one to each switch    then you bond then in an etherchannel
Two NICs going to TWO switches.
Content switches.


Datacenter 3.0
Load balancer
SSL offload
Firewall
IPS

At access layer you can always stick a QoS classification.

VLANS
ISL is cisco  it tags before and after the packet.
802.1Q  is Vlan  it marks it inside the packet.
802.1P  uses 3 bits for Priority.

Mark 802.1P as close to the source as you can.

Multicast.
To avoid flooding the hosts use.
CGMP   Cisco
IGMP   iEEE

CGMP the switch will query the router for the MACs of recipients.
IGMP the switch listens to messages from the hosts  to the router like  join or leave