Chapter 2 - section 2.1 - Explain charactersistics of routing technologies

section 2.1

Objective – Routing and Address Translation

• Static routing
• Dynamic routing
▸ Border Gateway Protocol (BGP)
▸ Enhanced Interior Gateway Routing Protocol (EIGRP)
▸ Open Shortest Path First (OSPF)
• Route selection
▸ Administrative distance
▸ Prefix length
▸ Metric
• Address translation
▸ Network Address Translation (NAT)
▸ Port Address Translation (PAT)
• First Hop Redundancy Protocol (FHRP)
• Virtual IP (VIP)
• Subinterfaces

Routing – Static Routing

• Routes manually configured by administrator
• No automatic updates
• Low overhead and predictable
• Not scalable for large networks
• Used in small or simple networks (N10-009)

Routing – Dynamic Routing

• Routes learned automatically
• Uses routing protocols
• Scales well in large networks
• Adapts to network changes
• Requires more resources than static routing

Dynamic Routing Protocol – BGP

• Border Gateway Protocol
• Exterior Gateway Protocol (EGP)
• Used between autonomous systems
• Path-vector protocol
• Common on the internet (exam critical)

Dynamic Routing Protocol – EIGRP

• Enhanced Interior Gateway Routing Protocol
• Cisco proprietary (now partially open)
• Hybrid routing protocol
• Uses composite metric
• Fast convergence

Dynamic Routing Protocol – OSPF

• Open Shortest Path First
• Link-state routing protocol
• Uses cost metric
• Fast convergence
• Common IGP in enterprises (exam critical)

Route Selection – Administrative Distance

• Trustworthiness of a routing source
• Lower value is preferred
• Static routes usually have lower AD
• Used when multiple protocols advertise same route

Route Selection – Prefix Length

• Also called longest prefix match
• More specific route is preferred
• Example: /24 preferred over /16
• Evaluated before metric

Route Selection – Metric

• Cost value used by routing protocols
• Lower metric is preferred
• Metric type depends on protocol
• Used after AD and prefix length

Address Translation – Network Address Translation (NAT)

• Translates private IPs to public IPs
• Conserves public IPv4 addresses
• Allows internet access for private networks
• Common on edge routers (N10-009)

Address Translation – Port Address Translation (PAT)

• Many private IPs share one public IP
• Uses different source port numbers
• Also called NAT overload
• Most common NAT implementation

Redundancy – First Hop Redundancy Protocol (FHRP)

• Provides gateway redundancy
• Prevents single point of failure
• Hosts use a virtual gateway address
• Examples: HSRP, VRRP, GLBP

Redundancy – Virtual IP (VIP)

• Shared IP address among routers
• Used by FHRP
• Clients use VIP as default gateway
• Automatically fails over

Routing Configuration – Subinterfaces

• Logical interfaces on a physical interface
• Used for VLAN routing
• Common with router-on-a-stick
• Enables inter-VLAN routing

N10-009 Sample Questions – Routing and NAT

• Q: Which routing protocol is used on the internet?
▸ A: BGP
• Q: Which route is preferred: /24 or /16?
▸ A: /24
• Q: Which NAT type allows many devices to share one public IP?
▸ A: PAT
• Q: Which protocol provides gateway redundancy?
▸ A: FHRP
• Q: What is required for router-on-a-stick?
▸ A: Subinterfaces