Network+ N10-007 ExamNotes for sub-objective 1.3 Explain the concepts and characteristics of routing and switching – Part 2 of 3
CompTIA Exam Sub-objective 1.3: “Explain the concepts and characteristics of routing and switching.”
Routing protocols (IPv4 and IPv6) – Distance-vector routing protocols – RIP – EIGRP – Link-state routing protocols – OSPF – Hybrid – BGP – Routing types – Static – Dynamic – Default
Addressing – Tunneling – Dual stack – Router advertisement – Neighbor discovery
For the rest of the 1.3 objectives go to Part 3.
Distance-vector Routing protocols (IPv4 and IPv6)
Routers use routing protocols to determine the best path for communication. The protocols evaluate the reliability and the priority of data using three metrics.
- Administrative distance (AD) assigns a numeric rating value to the protocol for prioritization. The lower the number the higher the priority. Administrators can modify this value to give one protocol precedence over another.
- Convergence time. This measures the time it takes the protocol to determine the best path when there are changes or outages along the route.
- Overhead measures the amount of resources needed to support the protocol.
Distance-vector routing protocols
Distance –vector routing protocols can use metrics as simple as the number of hops or they can calculate the latency and congestion. Neighboring routers can exchange this route information with each other. The protocols rely heavily on the routes they receive because they can’t measure network conditions more than two hops away. RIP (Routing Information Protocol), RIPv2 (Routing Information Protocol, version 2) and EIGRP (Enhanced Interior Gateway Routing Protocol) are distance-vector protocols. EIGRP is generally preferred over RIP.
See Distance-vector routing protocols.
See Distance-vector routing protocols.
Link-state routing protocols
Link-state protocols allow routers to communicate with routers beyond the two hop limit of distance-vector protocols. OSPF (Open Shortest Path First) is a link-state routing protocol. The best path to a destination can be determined using a network map it creates from the other routers. Link-state protocols adapt quickly to network changes. OSPF was developed to improve RIP. OSPF is stable, converges quickly, and supports large networks.
The Border Gateway Protocol is considered a hybrid protocol in the CompTIA objectives as it employs elements of both Link-state and distance-vector protocols. Technically it is classified as an advanced protocol.
When using static routing a network administrator specifies the paths between networks in the routing table. This is efficient and has low overhead, but it cannot compensate for network failures without manual intervention.
Dynamic routing has the capability of determining the best path between networks. This method also allows the router to detect and compensate for network issues like congestion by rerouting the communication. When new routers are discovered or added their routing tables are updated.
Default routing is a variant of static routing. A normal static route specifies communication between two known networks. A default route is configured to send packets destined to any unknown destination to the next hop address.
IPv6 addresses consist of eight hexadecimal blocks separated by colons. Each block contains 16 bits making the IPv6 address 128 bits in length.
Here’s an example: 2001:0db8:85a3:0000:0000:8a2e:0370:7334
If an IPv6 address block contains all zeroes it can be truncated using double colons (::). The example address can be truncated to 2001:0db8:85a3::8a2e:0370:7334.
Tunneling aids the transition from IPv4 to IPv6 by allowing IPv6 routers and hosts to communicate with each other over the existing IPv4 infrastructure. To accomplish these IPv6 datagrams are encapsulated within IPv4 packets and travel on the IPv4 network. The IPv6 datagram is extracted by the IPv6 destination device.
A network that uses both IPv4 and IPv6 is called dual stacked. Dual-stacked packets will not be handled by networks that do not support it. The solution is to tunnel these packets. The best example is the internet which is not completely dual stacked. All IPv6 internet traffic uses tunneling.
Router advertisement is used as part of IPv6 autoconfiguration. An IPv6 host can auto-configure its own address. In this process, the host uses a standard prefix with its interface ID based on the host MAC address. The host requests configuration information from the router in a message called a router solicitation (RS). The router responds with a router advertisement (RA) containing the necessary configuration information.
The Neighbor Discovery Protocol (NDP) is part of the IPv6 protocol suite. It serves as a replacement for IPv4 for ARP and ICMP and others. NDP uses five message types:
- Router Solicitation-The Router Solicitation message is sent by IPv6 hosts to discover the presence of IPv6 routers on the link.
- Router Advertisement – The Router Advertisement message contains the information required by hosts to determine whether or not to use address autoconfiguration, the link prefixes, MTU, specified routes.
- Neighbor Solicitation – IPv6 nodes send the Neighbor Solicitation message to discover the link-layer address of an IPv6 node on-link.
- Neighbor Advertisement – The Neighbor Advertisement contains the information required by nodes to determine the sender’s role on the network, and typically the link-layer address of the sender.
- Redirect – An IPv6 router will send a Redirect message by to inform a host of a better first hop address for a specific destination.