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20 Cards in this Set
- Front
- Back
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What were some TCP/IP developments that helped deal with the limited number of IPv4 addresses available?
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Network Address Translation (NAT), along with private addressing, allowed organizations to use unregistered IP addresses internally and still connect to the internet. Classless Interdomain Routing (CIDR) allowed ISPs to reduce waste by assigning a company a small subnet of a network rather than an entire network. CIDR also allows ISPs to summarize routes which helps reduce the size of the routing tables on the internet routers.
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What are the private address spaces reserved for internal use at organizations?
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A - 10.0.0.0 to 10.255.255.255 B - 172.16.0.0 to 172.31.255.255 C - 192.168.0.0 to 192.168.255.255
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Define static NAT
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The gateway router has a static one-to-one mapping for private addresses and public addresses. For every internal computer that needs to connect to the internet you need a separate public IP to use.
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What terms does Cisco use to refer to NAT addresses?
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inside local refers to the private IP address, and inside global refers to the public IP address.
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When are outside local and outside global used?
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When you are performing NAT translation on packets entering the network, and representing an internet host as being on the local network.
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Define dynamic NAT
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The gateway router has a pool of public (inside global) IP addresses. As inside hosts connect to outside hosts, the router temporarily maps each inside local IP address to an inside global IP address.
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How many concurrent connections can dynamic NAT support?
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The number of IP addresses defined in the NAT pool
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How can you increase the number of concurrent connections supported by dynamic NAT translation?
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Using Port Address Translation (PAT) (also called NAT overload by Cisco) to translate port numbers as well as IP addresses. Because the port number field hsa 16 bits, NAT overload can support up to 65,000 concurrent connections using a single inside global IP address.
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How would you enable dymanic NAT with a pool of 200.200.153.1 to 200.200.153.254?
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ip nat inside; ip nat pool fred 200.200.153.1 200.200.153.254 mask 255.255.255.0;
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How would you clear the NAT translation table?
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clear ip nat translation *
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How would you enable IP NAT overload, using ACL list 1 to match packets, and using the IP address assigned to the Serial0/0 interface as the inside global IP address?
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ip nat inside; ip nat inside source list 1 interface Serial0/0 overload;
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What are the different kinds of ICMP messages?
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Internet Control Message Protocol messages: Destination unreachbale, time exceeded, redirect, and echo.
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What are the different kinds of destination unreachable codes sent by ICMP?
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Network unreachable, host unreachable, can't fragment, protocol unreachable, and port unreachable.
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When is a network unreachable code used?
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By a router, to inform the sender that there is no match in a routing table for the destination address.
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When is a host unreachable code used?
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By a router, to inform the sender that the packet can be routed to the destination subnet but the host is not responding.
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When is a can't fragment code used?
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By a router, when the "Don't fragment" bit is set on the packet, to inform the sender that it must fragment the packet to forward it.
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When is a protocol unreachable code used?
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By the endpoint host, to inform the sender that the packet arrived but there is no transport layer protocol available.
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When is a port unreachable code used?
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By the endpoint host, to inform the sender that the packet arrived but the destination port has not been opened by an application.
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What is the trace command and how does it work?
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It does the same thing as traceroute. It sends packets starting with TTL 1 and incrementing by 1 each time. That way it can map the routing path the packets travel.
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What is secondary addressing?
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Assigning multiple IP addresses to the same interface on a router.
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