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A wildcard mask is a mask of bits that indicates which parts of an IP address are available for examination. In the Cisco IOS, [1] they are used in several places, for example: To indicate the size of a network or subnet for some routing protocols, such as OSPF. To indicate what IP addresses should be permitted or denied in access control lists ...
For example, to do a reverse lookup of the IP address 8.8.4.4 the PTR record for the domain name 4.4.8.8.in-addr.arpa would be looked up, and found to point to dns.google. If the A record for dns.google in turn pointed back to 8.8.4.4 then it would be said to be forward-confirmed.
Packet Tracer is a cross-platform visual simulation tool designed by Cisco Systems that allows users to create network topologies and imitate modern computer networks. The software allows users to simulate the configuration of Cisco routers and switches using a simulated command line interface.
In standard unicast IP routing, the router forwards the packet away from the source to make progress along the distribution tree and prevent routing loops. In contrast, the router's multicast forwarding state runs more logically by organizing tables based on the reverse path, from the receiver back to the root of the distribution tree at the ...
When performing a reverse lookup, the DNS client converts the address into these formats before querying the name for a PTR record following the delegation chain as for any DNS query. For example, assuming the IPv4 address 208.80.152.2 is assigned to Wikimedia, it is represented as a DNS name in reverse order: 2.152.80.208.in-addr.arpa.
EDNS support is also needed to allow for the much larger packet sizes that DNSSEC transactions require. When the resolver receives an answer via the normal DNS lookup process, it then checks to make sure that the answer is correct. Ideally, the security-aware resolver would start with verifying the DS and DNSKEY records at the DNS root.
DHCP has a higher priority than DNS: if DHCP provides the WPAD URL, no DNS lookup is performed. This only works with DHCPv4. In DHCPv6, there is no WPAD-Option defined. When constructing the query packet, DNS lookup removes the first part of the domain name (the client host name) and replaces it with wpad. Then, it "moves up" in the hierarchy ...
The Neighbor Discovery Protocol (NDP), or simply Neighbor Discovery (ND), is a protocol of the Internet protocol suite used with Internet Protocol Version 6 (IPv6). [1]: §1 It operates at the internet layer of the Internet model, [2] and is responsible for gathering various information required for network communication, including the configuration of local connections and the domain name ...