The document provides an overview of routing concepts, including the importance of metrics like hop count, bandwidth, and latency in determining optimal routing paths. It discusses techniques for route aggregation to manage routing tables efficiently and highlights high availability methods such as HSRP and VRRP to prevent network downtime. Educational qualifications and expertise related to IT management and network administration are also detailed.

1. Introduction
to routing
concepts II.

2. Page 2
Instructor, PACE-IT Program – Edmonds Community College
Areas of Expertise Industry Certifications
 PC Hardware
 Network Administration
 IT Project Management
 Network Design
 User Training
 IT Troubleshooting
Qualifications Summary
Education
 M.B.A., IT Management, Western Governor’s University
 B.S., IT Security, Western Governor’s University
Entrepreneur, executive leader, and proven manger
with 10+ years of experience turning complex issues
into efficient and effective solutions.
Strengths include developing and mentoring diverse
workforces, improving processes, analyzing
business needs and creating the solutions
required— with a focus on technology.

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PACE-IT.
– Routing metrics.
– Route aggregation.
– High availability.

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Introduction to routing concepts II.

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There may be more than one
route available to a remote
network. Routing protocols use
metrics to determine which
route is the best route to use.
Each routing protocol will use its own set of metrics
in determining which routes to which networks are
placed in its routing table.
The same basic metric may be used by different
routing protocols. When this occurs, the metric is
usually implemented in a different manner through
the use of different algorithms.
Introduction to routing concepts II.

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Introduction to routing concepts II.
– Hop count.
» The number of routers between two end points.
• Determined from the sending router’s perspective.
– Maximum transmission unit (MTU).
» The maximum allowed size of a packet, measured in bytes.
• The standard MTU for Ethernet is 1500 bytes.
» Packets that exceed the MTU must be fragmented into small
pieces, leading to more packets, leading to slower connection.
– Bandwidth.
» A measure of the speed of the network connection.
• The speed can be measured in Kbps, Mbps, or Gbps.
– Latency.
» A measure of time that a packet takes to traverse a link.
• When implemented by routing protocols, the total amount of
latency (or delay) to go end to end between two points is
used.

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Introduction to routing concepts II.
– Administrative distance (AD).
» The believability of a routing protocol’s advertised routes.
• Different routing protocols are considered to be more
believable (trustworthy) than others.
» Routers use the AD to help determine which routing protocol to
use when more than one protocol is installed on the router.
» The lowest AD of an advertised route will determine the
protocol used.
» Common standard ADs:
• Directly connected route = 0 (no protocol required).
• Statically configured route = 1 (no protocol required).
• E-BGP = 20.
• Internal EIGRP = 90.
• OSPF = 110.
• IS-IS = 115.
• RIP = 120.
• External EIGRP = 170.
• I-BGP = 200.
• Unknown = 255 (not believable).

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Introduction to routing concepts II.

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Without some mechanism
put in place, routing tables
soon become very large and
highly inefficient.
Through careful planning, network administrators
use a process called route aggregation to condense
the size of routing tables. They do so through the
use of Classless Inter-Domain Routing (CIDR) to
summarize routes to different networks. Route
aggregation is common in networking.
Introduction to routing concepts II.

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Introduction to routing concepts II.
– Example of route aggregation.
» Networks connected to interface S/0/1:
• 10.1.1.0/24.
• 10.1.17.0/24.
• 10.1.32.0/24.
• 10.1.128.0/24.
» These routes could be summarized (aggregated) by a common
CIDR entry in a routing table:
• 10.1.0.0/16.
– Warning on route aggregation.
» Route aggregation takes careful planning during the network
design phase.
• The above example would not work if interface s/1/1 on the
same router was connected to network 10.1.2.0 (this is an
example of non-contiguous networks).

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Introduction to routing concepts II.

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Part of a network
administrator’s job is to
ensure that networks
remain up and active for the
maximum amount of time.
In an effort to ensure that networks don’t go down,
administrators often remove single points of failure.
A single point of failure in a network is the point where a
single failure will cause the network to cease functioning.
Network administrators often use high availability
techniques in order to remove those single points of
failure. An example of a high availability technique is the
use of redundant links to outside networks.
Introduction to routing concepts II.

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Introduction to routing concepts II.
– Hot Standby Router Protocol (HSRP).
» HSRP is a proprietary Cisco method of creating a fault tolerant
link using two or more routers with connections outside of the
local subnet.
• The two routers are connected together as well as having
connections outside of the local network.
• A virtual IP address is created and shared between the
routers.
• Devices on the network are configured to use the virtual IP
address as the default gateway for packets leaving the
network.
• If a router goes down, the link outside of the network is still
available.
– Virtual Router Redundancy Protocol
(VRRP).
» VRRP is an IETF (Internet Engineering Task Force) standard
that is similar in operation to HSRP.

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Routing protocols use metrics to determine which route is the best route to
use to reach remote networks. Routing protocols can use the same metrics,
but will use different algorithms to populate their routing tables. Common
metrics include: hop count, MTU, bandwidth, latency, and AD.
Topic
Routing metrics.
Summary
Without some planning, routing tables can become large and inefficient.
Route aggregation is a method of summarizing routes to different networks
through the use of CIDR. Care and caution must be used when non-
contiguous networks are present.
Route aggregation.
Network technicians use high availability techniques in an effort to remove
single points of failure from networks. HSRP and VRRP are examples of
high availability techniques that are implemented to reduce the chances that
a single router going offline will create a problem for the network.
High availability.
Introduction to routing concepts II.

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