is452exam3review

• Flash
• NVRAM
• RAM

• Memory where IOS image is kept
• copies of the configuration can also be kept in this space

Maintains the configuration of the device

• Volatile memory where the running configuration is kept
• CPU executes IOS software
• Routing tables are maintained

• Console Port
• Auxiliary (Aux) port
• VTY Virtual terminal line (Telnet)

A terminal connection attached to a computer

Used for out-of-band access via a modem

Access to device through telnet session

• Saving Configuration
• § Running Configuration
• ○ The configuration that is used while the system is on
• § Start-up Configuration
• ○ The configuration that is loaded onto the system when the system is started
• ○ Once started, the configuration becomes running configuration
• § copy running-config startup-config is the syntax used to save the configuration

The configuration that is used while the system is on

• The configuration that is loaded onto the system when the system is started
• Once started, the configuration becomes running configuration

• An access point to the Internet
• A router is required to interface with the service provider
• § A CSU/DSU is required for leased lines
• § CSU/DSU is a hardware device that converts a digital data frame used on the LAN into one that is appropriate for the WAN or Internet
• Demarcation point is where the ISP company ends and the private network of the customer begins
• Last mile handled by local LEC
• A circuit can be a partial T1 to an OC-255(13.21 Gbps)

Is where the ISP company ends and the private network of the customer begins

Is a hardware device that converts a digital data frame used on the LAN into one that is appropriate for the WAN or Internet

• A segment or subnetwork that sits between a trusted internal network and an untrusted external network
• ○ Typically DMZ include web, FTP, SMTP, and DNS servers
• ○ A DMZ can reside off of a router or firewall
• ○ *diagram

• DS1 (T1) Circuit
• E1 Circuit (Used in Europe)
• DS3 (T3)Circuit
• E3 Circuit (Used in Europe)
• OC3 Circuit
• OC12 Circuit

• A connection supporting data rate of 1.544Mb (Actually consists of 24 channels each being 64Kb)
• Acquiring multiple or fractional T1s are options.
• ○ Half of a T1 – 768Kb
• ○ Two T1s – 3.088Mb

A connection supporting data rate of 2.048Mb (32 channels)

A connection supporting data rate of 44.736Mb (28 DS1s, plus management overhead)

A connection supporting data rate of 34.064Mb (16 E1s, plus management overhead)

A connection supporting data rate of 155Mb

A connection supporting data rate 622Mb

• Time interval between the transmission of a packet and the reception at its destination – usually measured as Round Trip Time
• Network Latency is a component of “response time”
• ○ Response time also includes delays inherent in applications, servers and clients

• Distance – Speed of Light (Fiber length)
• Serialization Delay (very small contribution to delay)
• • Time to place a frame on the network
• Queuing Delay - Network Congestion
• • Waiting till other packets finish transmission for an opportunity to transmit
• • Varies from less than 1 mS to over 10,000 mS

Time to place a frame on the network

• Waiting till other packets finish transmission for an opportunity to transmit
• Varies from less than 1 mS to over 10,000 mS

• Set Expectations
• • Some applications are not meant to work over high latency
• Avoid Congestion
• Use adequate Data Rates

• Is the act of moving information from a source to a destination
• Routing occurs at layer 3 of the OSI model

• Determining optimal path to destination
• • Metrics are used by routing protocols to determine path
• • Path information is kept in routing tables
• ○ These tables can vary depending on what protocol was used to acquire path
• ○ Routers communicate with each other and maintain their routing tables through the exchange of messages
• Transporting packets across network
• ○ This is same across most routing protocols

Various different algorithms exist and each has a different impact on network and router

• Optimality
• Simplicity
• Robust
• Convergence
• Flexibility

This is the capability and criteria in selecting the optimal path

These algorithms are overhead so they must not take up to many resources of the router

They should be able to determine correct paths in cases of high load, hardware failure, and incorrect implementations

This the process of agreement, by all routers, on optimal paths. This process must occur quickly

They should be able to adapt quickly to changing circumstances

• Static Routing vs Dynamic
• Single Path vs Multipath
• Flat vs Hierarchical
• Link State vs Distance Vector

• Static
• ○ These are mappings that the network engineer has manually coded into the routing device
• ○ These mappings do not change unless they are manually changed
• ○ Simple to design and work well where network design is simple
• Dynamic
• ○ Uses a routing table
• ○ Path changes and routing table updates are made automatically

Does the routing protocol allow for multiple paths to the destination

• In a flat environment all routers are all peers
• In hierarchical some routers form the backbone
• ○ Some routers can talk to all while other routers can only talk to their specific area

• In link state routers send their own routing information to all routers within the network
• In distance vector routers send their routing table information only to their neighbors
• Link state have faster convergence but use more resources of the router

• Path length
• Reliability
• Routing delay
• Bandwidth
• Load
• Communication cost

This calculates the cost associated with each link

The dependability of a network link

The amount it takes to move a packet from source to destination

The traffic capacity of the link

Determines how busy a router is

The cost in dollars for moving a packet across the line

• Routers add directly connected subnets to their routing table
• Routers send updates to neighbors with their routing tables
• Routers listen for routing updates from neighbors
• Routing information includes a subnet number and a metric
• When possible routers use broadcasts or multicast to send updates
• If multiple paths are learned it will use the one with the best metric
• Routers send and expect to receive periodic updates
• If update is not received it results in the removal of the route

*diagram

Once a link has failed, a very large metric is used for that route

• Routing information is never sent out the interface it was received on.
• *diagram

• When learning that a route has failed, ignore any information about an alternative route to the subnet for a time equal to the hold-down timer.
• *diagram

• SOHO, Branch Office, Central Site
• • Different size sites will have different requirements
• • Some of the determining factors in selecting a router are cost, availability, throughput, and additional features
• • Service Providers (ISP) have a different line of routers available to them
• • Cisco has added the 800, 1900, 2900, and 3900 Integrated Service routers
• • Integrated routers allow one box to be the router, security device, VPN Gateway, WAP, Switch, IP Telephony Call Manger, etc…

• RIP updates are sent every 30 seconds
• A router updates its routing table once it receives an update and increments the path metric to the destination network by 1
• RIP only maintains the best path to the remote network which is based on hop metric
• • Could case unoptimal paths
• Routing updates are sent independently of the regularly scheduled updates
• RIP is very easy to configure
• RIP does not support VLSM

• RIP only uses the hop count metric
• • Each hop has a value of 1
• The maximum number of hops allowed in a path are 15
• • If a router receives an update that increases the metric for a network to be 16 then that network is considered to be unreachable

• RIP only requires two commands to be enabled
• *table

• IGRP was developed by Cisco in the mid 80s
• The goal was to provide a robust routing protocol with an autonomous system
• • Autonomous system is collection of networks under a common administration sharing a common routing strategy
• • Can also be thought of as a routing domain
• IGRP uses a metric that factors delay, bandwidth, reliability, and load
• • Network administrators can change these values and influence route selection
• • Bandwidth metric is set on the specific interface
• IGRP permits multipath routing
• IGRP does not support VLSM

• IGRP only requires two commands to be enabled
• *table

Access lists are used to filter traffic that passes through a router

• Packets can be filtered as they enter an interface
• Packets can be filtered before they exit an interface
• Deny is the term used in Cisco IOS to block a packet at the interface that is doing the filtering
• Permit is the term used in Cisco IOS to allow a packet through the interface that is doing the filtering
• At the end of every ACL is an implied “deny all traffic” statement. Therefore, if a packet does not match any of your access list statements, it is blocked

IP, TCP, and UDP headers in the packet

• The standard ACL only examine the source IP address
• The extended ACL can examine the source and destination IP address, as well as the source and destination port numbers

• ACLs use a wildcard mask instead of a subnet mask
• Wildcard masks are the inverse of the subnet mask, the 1s are 0s and the 0s are 1s

1 to 99 or 1300 to 1999

• “access-list|number|permit/deny|ip address|wildcard mask”
• “access-list 1 permit 172.16.0.0 0.0.255.255”
• “access-list 1 deny 165.31.0.0 0.0.255.255”
• Configuration is done in configuration mode

• The command used to apply an ACL to an interface is “ip access-group”
• • This command is run under the interface mode
• • To enable an ACL The interfaces on router need to be designated as the “inside” and “outside” interface
• • “ip access-group 1 out” or “ip access-group 1 in”

100 to 199 or 2000 to 2699

• “access-list|number|permit/deny|protocol|source IP address|source wildcard mask|destination IP address|destination wildcard mask|eq|port number”
• “access-list|101|permit|tcp|172.16.0.0|0.0.255.255|165.33.15.0|0.0.0.255|eq|23”
• “access-list 101 deny udp host 130.85.5.5 209.80.1.0 0.0.255.255 eq 80”
• • “host” can be used to specify one ip address
• • “eq” stands for equal and is telling the exact port to filter traffic on
• • Ports can be compared by using less than (lt) or greater than (gt)
• • Configuration is done in configuration mode

• The command used to apply an ACL to an interface is “ip access-group”
• • This command is run under the interface mode
• • To enable an ACL The interfaces on router need to be designated as the “inside” and “outside” interface
• • “ip access-group 101 out” or “ip access-group 101 in”

“access-list 101 remark this access list is used to deny web traffic”