Enterprise Network Architecture Flashcards
Hierarchical Lan Design
A Hierarchical Lan design model divides the enterprise network architecture into modular layers.
Each Layer implements a specific Function
Makes the network easier to scale
Provides fault isolation
Facilitates easier troubleshooting
Access Layer
The network edge, where end-user devices or endpoints connect to the network
Modular Building Blocks
Access Layer > Gives endpoints and users direct access to the network
Distribution Layer > Provides an aggregation point for the access layer and acts as a services and control boundary between access layer and the core layer.
Core Layer (Backbone) > Provides connections between distribution layers for large environments
Tier 2 Design or Collapsed Core
Single Building may require only distribution and Access Layers
Scale Out Core Layer
Scale boxes horizontally
Scale up means increate the capacity of an individual box vertically
Access Layer
PC, IP Phones, wireless access points, Printers, IP cameras
High bandwidth Access
First hop QoS trust points
Segmented using VLANS, different logical network
Communication between access blocks through distribution blocks
Distribution Layer (Aggregation BLock)
Aggregate access layer switches in the building
Distribution switches should be deployed in pairs for redunduncy
Stateful Switch Over (SSO) supported in chassis basis solutions
Same for core layer
Interconnect with each other with layer 2 or layer 3
THe Core Layer
Backbone and aggregation point for multiple networks
High speed connectivity between distribution blocks
- THe WAN
- The Internet
- The Datacenter
- THe network Service Layer
Enterprise network Design
2 Tier Design
3 Tier Design
Layer 2 Access (STP from access to distribution)
Layer 3 Access (Layer 3 routing from access to distribution)
Simplified Campus Design
Software Defined Access (SD-Access)
2 Tier Design
Smaller Networks May not require a core layer
Distribution layers acts as the core layer
connects southbound to access layer switches
connects northbound to WAN, Serve Farm, Internet and network services
3 Tier Design
Core Switches connect t pairs of distribution switches using a layer 3 protocol, OSP or EIGRP
Layer 2 Access
Distribution Layer hosts default gateways for end stations
Loops in the layer 2 network cause STP to block links, redundant uplinks from access to distribution remain unutilized
Recommendation is to limit a VLAN to an individual access switch
Loops can be removed using layer 3 links between distribution switches
not possible IF VLAN s need to span between multiple access switches
FHRP (First Hop Redundancy Protocol)
Layer 2 Access, distribution switches are the default gateways for end hosts
FHRP should be run between Distribution switches to provide default gateway redundancy
Hot Standby Router Protocol (HSRP)
Virtual Router Redundancy Protocol (VRRP)
Gateway Load Balancing Protocol (GLBP)
HSRP
Active/Standby redundancy of DG
Switches aggree on VIrtual IP AND Virtual Mac Address of DG
End Stations ARP (address resolution protocol) request and returned a virtual mac address
One distribution switch is the active forwarder and one is standby gateway
redundant links may be underutilized
multiple copies of HSRP, under utilized links
VRRP
Open Standard equivalent of HSRP
Switches aggree on VIrtual IP AND Virtual Mac Address of DG
End Stations ARP (address resolution protocol) request and returned a virtual mac address
One distribution switch is the active forwarder and one is standby gateway
redundant links may be underutilized
multiple copies of HSRP, under utilized link
GLBP
Active/Active FOrwarding for both distribution switches
Switches agree on Virtual IP and multiple MAC ADDRESS of the DG
End stations ARP for Default gateway and re returned one of the virtual mac address
load balancing occurs because some end sataions point to one MAC address other point towards second mac address
still not he best solution as end host traffic is not always 50/50 split eng traffic is load balanced per host not per flow
Layer 3 access
Access to distribution trunk links are replaced with layer 3 routed links
access layer switches now participate in routing protocols eg, ospf eigrp
access switches are now DG for end hosts
removes the need to FHRP
Removes the need for SPaning tree protocol
Load balancing based on layer 3 routing
load balacing can now occur per flow
increases uplink bandwidth utilization
Easier troubleshooting
faster convergence now function of OSPF and EIGRP
No spanning vlan bwtween multiple access switches
Simplified Campus Design
Uses clustering techniques such as virtual switching system VSS or Stackwise where multiple switches act as one
NO FHRP
NO STP
access layers uses port-channel
Incrase ulink utilistion
reduce convergece time
distributed VLANS
simplified management
