READ Free Dumps For CISCO- 100-105
| Question ID 14619 | Under which circumstance should a network administrator implement one-way NAT?
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| Option A | when the network must route UDP traffic
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| Option B | when traffic that originates outside the network must be routed to internal hosts
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| Option C | when traffic that originates inside the network must be routed to internal hosts
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| Option D | when the network has few public IP addresses and many private IP addresses require outside access
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| Correct Answer | B |
Explanation Explanation: NAT operation is typically transparent to both the internal and external hosts. Typically the internal host is aware of the true IP address and TCP or UDP port of the external host. Typically the NAT device may function as the default gateway for the internal host. However the external host is only aware of the public IP address for the NAT device and the particular port being used to communicate on behalf of a specific internal host. NAT and TCP/UDP "Pure NAT", operating on IP alone, may or may not correctly parse protocols that are totally concerned with IP information, such as ICMP, depending on whether the payload is interpreted by a host on the "inside" or "outside" of translation. As soon as the protocol stack is traversed, even with such basic protocols as TCP and UDP, the protocols will break unless NAT takes action beyond the network layer. IP packets have a checksum in each packet header, which provides error detection only for the header. IP datagrams may become fragmented and it is necessary for a NAT to reassemble these fragments to allow correct recalculation of higher-level checksums and correct tracking of which packets belong to which connection. The major transport layer protocols, TCP and UDP, have a checksum that covers all the data they carry, as well as the TCP/UDP header, plus a "pseudo-header" that contains the source and destination IP addresses of the packet carrying the TCP/UDP header. For an originating NAT to pass TCP or UDP successfully, it must recompute the TCP/UDP header checksum based on the translated IP addresses, not the original ones, and put that checksum into the TCP/UDP header of the first packet of the fragmented set of packets. The receiving NAT must recompute the IP checksum on every packet it passes to the destination host, and also recognize and recompute the TCP/UDP header using the retranslated addresses and pseudo-header. This is not a completely solved problem.
| Question ID 14620 | Which routing protocol has the smallest default administrative distance?
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| Option A | IBGP
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| Option B | OSPF
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| Option C | IS-IS
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| Option D | EIGRP
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| Option E | RIP
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| Correct Answer | D |
Explanation Explanation: http://www.cisco.com/c/en/us/support/docs/ip/border-gateway-protocol- bgp/15986-admin-distance.html Default Distance Value TableThis table lists the administrative distance default values of the protocols that Cisco supports: Route Source Default Distance Values Connected interface Static route Enhanced Interior Gateway Routing Protocol (EIGRP) summary route External Border Gateway Protocol (BGP) Internal EIGRP IGRP OSPF Intermediate System-to-Intermediate System (IS-IS) Routing Information Protocol (RIP) Exterior Gateway Protocol (EGP) On Demand Routing (ODR) External EIGRP Internal BGP Unknown* 255