CompTIA Chapter 5 Topic A... Explain Characteristics of Routing
Interior Gateway Routing Protocol (IGRP)
Provides a routing protocol for routing within a domain or autonomous system.
Routing algorithm metrics - MTU (Maximum transmission unit)
How large a packet can be sent without the need for fragmentation
Derive the network ID
Masking the full IP address against a network prefix or subnet mask
The maximum hop count is (To prevent looping)
15
Routing algorithm metrics - Load
A metric that bases routing decisions on how busy a route is
Black hole
A packet is discarded without notificiation back to the source
Metric
A preference balue assigned to the route, with low values being preferred over high ones. The value of the metric may be determined by different parameters.
Learned route
A route that was communicated to the router by another router by using dynamic routing protocol
route aggregation
A supernet configuration implemented for the purpose of reducing the number of routing table entries by combining several entries, one for each network, into one entry that represents multiple networks.
Distance vector
Algorithms require that routers periodically propagate their entire routing table to their immediate neighbors.
Classless Inter-Domain Routing (CIDR)
Allows network administrators to expand the number of network nodes assigned to an IP address.
Open shortest path first (OSPF)
An interior gateway routing protocol developed for IP networks based on the shortest path first or link-state algorithm.
BGP port
BGP works over TCP on port 179
Backbone (Area 0)
Created by the collection of border routers.
Routing table entries category
Default routes, which are used when a better network or host route is not found.
Switches
Devices communicate with different network segments through these. They are limited to hosts within the same broadcast domain (link-local)
Routing table entries category
Direct network routes, for subnets to which the router is directly attached
Modern routers use
Dynamic Routing Protocol
Enhanced Interior Gateway Routing Protocol (EIGRP)
Enhanced version or IGRP which allows classless addressing, replaced IGRP making IGRP obsolete
Routing algorithm
Formula that is stored in the router's memory. Makes decisions for the router concerning the best path for data.
Routing table entries category
Host routes, for routes to a specific IP address
End systems (ESs)
Hosts with no capcity to forward packets to other IP networks are refferred to as
Routing Table
Information about the location of other IP networks and hosts is stored in this.
Routing algorithm metrics - Latency
It takes time for a packet to traverse an internetwork. Delay-based metrics measure transit time. This metric is most important if the route is used to carry time-sensitive data, such as voice or video
Dynamic Routing Protocol
Learn about remote networks and the most efficient route to these networks.
Static routing
Means that you manually add routes to a routing table, and they change only if you edit them. Configuring static routing entries can be useful in some circumstances, but it can be problematic if the routing topology changes often, as each route on each affected router needs to updated manually.
IP datagram (89)
Messages sent using OSPf's own datagram format
Routing algorithm metrics - Bandwidth
Metrics based on bandwidth look at the maximum achievable bandwidth on a link and do not consider the available bandwidth. This is a less efficient metric than delay-based metrics
Steady state
Network where all the routers share the same topology
Routing algorithm metrics - Reliability
Over time, it might become obvious that some links between routers are more reliable than others. You can assign a value for this reliability that routers can assess when determining an effective path
OSPF also supports
Plain text or cryptographic authentication
Ases
RFC 1930
Routing table entries category
Remote network routes, for subnets and IP networks that are not directly attached
Area borer routers
Routers that can connect to multiple areas
Intermediate systems (ISs)
Routers that interconnect IP networks and can perform this packet forwarding process are known as
Destination IP address and netmask
Routes can be defined to specific hosts but are more generally directed to network IDs
Flood broadcast traffic
Switches
Routing
Takes place when a host needs to communicate with a host on a different IP network or a different subnet
Rip considers only one route to a given destination network
That with the lowest HOP count
Gateway/next hop
The IP address of the next router along the path
Routing algorithm metrics - Path length
The end-to-end cost of using a route(hop count). You might assign a value to a path between router A and B and between B and C. The end-to-end path length is the sum of A-to-B and B-to-C
Interface
The local port to use to forward a packet along the chosen route
Prefixes are allocated in a hierarchical manner
The smaller prefix blocks, which contain more networks, going to internet registries, who then allocate mid-size blocks to ISPs who then allocate the blocks with the largest network prefixes to end users.
0.0.0.0/0
This is the all 0s default route. if a packet's destination address does not match any of the other entries, this is the route that will be used. The gateway for the route is Router A
192.168.1.255/32
This is the broadcast address for the 192.168.1.0/24 IP network
192.168.1.22/32
This is the host's own address, so any traffic for it, is directed ot the loopback itnerface
127.0.0.1/8
This is the loop back address for directing any communications back to the same host. This is used mostly for toubleshooting
192.168.1.0/24
This represents the host's local IP network, so it uses its 192.168.1.22 interfaces as the gateway to deliver packets to hosts on the same subnet, resolving IP addresses to MAC addresses by using ARP
BGP
Type of exterior gateway protocol
link-state advertisement (LSA)
Used to update a routing table. "Advertise" what routers they know of
RIP uses the what?
User Datagram Protocol (UDP port 520)
Riping(IPv6)
Uses UDP port 521
Early routers
Were manually configured with routing information.
Packet delivery
When a router receives a packet, it goes through the same process that the source host did to calculate if the packet needs to be routed to another router or it can be delivered locally to another interface(Directly connected route)
Routing algorithm metrics (Price/costs)
You can assign a monetary cost to various links, and the router using a cost metric will try to select the cheapest link available. This is useful for organizations routing on a budget.
High level network routing prefixes (CIDR blocks), /8
are allocated by the IANA to RIR, such as ARIN and RIPE. Few are held by private companies such as IBM, HP, AT&T
Routing Information Protocol (RIP)
is a long-established distance vector-based routing protocol. It uses a hop count metric to determine the distance to the destination network.
All IP hosts are capable of functioning as routers
but most workstation and server computers are configured with a single network adapter connected to only one network.
Loop
causes a packet to be forwarded around the network until its TTL(Time to live) expires
Border Gateway Protocol(BGP)
designed to be used between routing domains, or Autonomous Systems (ASes)
Routers (Interconnect)
desinged to connect inner networks and support connectivity to distant networks. 1. They use a routing table to determine the next hop interface to use to forward a packet 2. They can connect dissimilar layer 2 network segments. This strips the layer 2 header of an incoming packet and replaces it with the appropriate layer 2 header for the destination interface.
Classless IPv4 routing uses a mix of
flat and hierarchical structures to make more efficient use of the limited address space compared tot he old method of classful address allocation
EIGRP
is a native IP protocol, which means that it is encapsulated directly in IP datagrams, rather than using TCP or UDP.
Router Interface
is a seperate broadcast domain. Routers do not typically forward broadcast traffic, though this can be overridden vy config specific router setting (DHCP relay)
IPv6 interface
is always 64 bits
Interior gateway protocol (IGP)
is one that performs routing within a network under the administrative control of a single owner (Autonomous system (AS)
IPv6 network prefix
is only given in slash notation
Convergence
is the process whereby routers running dynamic routing algorithms agree on routes through the internetwork
Ethernet switches
make forwarding decisions based on layer 2 MAC addresses
Routers
make forwarding decisions based on layer 3 network addresses. These are typically IP addresses.
Exterior gateway protocol (EGP)
one that can perform routing between autonomous ystems.
Next hop
the destination router indicated by the outgoing interface entry in the routing table
In IPv4 the network prefix can be increased
to make more network numbers available(At the expense of the number of host IDs left available for each network.