Cisco CCNA Study Guide - Router Alley

More documents

Recommendations

Info

CCNA Study Guide v2.62 – Aaron Balchunas 274 DNS Zone File Example There are two types of zones in DNS: • Forward Lookup Zones - translates a host name to an IP address. • Reverse Lookup Zones - translates an IP address to a hostname (otherwise known as the IN-ADDR.ARPA zone). The following is an example zone file for the fictional example.com domain: $ORIGIN example.com $TTL 86400 @ IN SOA dns1.example.com. hostmaster.example.com. ( 2001062501 ; serial 21600 ; refresh after 6 hours 3600 ; retry after 1 hour 604800 ; expire after 1 week 86400 ) ; minimum TTL of 1 day IN NS dns1.example.com. IN NS dns2.example.com. IN MX 10 mail.example.com. IN MX 20 mail2.example.com. IN A 10.0.1.5 server1 IN A 10.0.1.5 server2 IN A 10.0.1.7 dns1 IN A 10.0.1.2 mail IN CNAME server1 mail2 IN CNAME server2 www IN CNAME server2 Entries within a zone file are referred to as DNS records. There are a variety of DNS record types, including: • NS (Name Server) – identifies a DNS server for the domain. • SOA (Start of Authority) – identifies the primary (authoritative) DNS server for the domain. • A (Address) – identifies an individual host in the domain. • CNAME (Canonical Name) – assigns an alias for another host name. • MX (Mail Exchanger) - identifies a mail server in the domain. • PTR (Pointer) - used for reverse DNS lookups. The number defined in the MX record is a priority. A lower priority is more preferred. * * * All original material copyright © 2013 by Aaron Balchunas (aaron@routeralley.com), unless otherwise noted. All other material copyright © of their respective owners. This material may be copied and used freely, but may not be altered or sold without the expressed written consent of the owner of the above copyright. Updated material may be found at http://www.routeralley.com.
CCNA Study Guide v2.62 – Aaron Balchunas 275 DNS Process DNS follows a strict process when performing a query. The process is as follows: 1. The local DNS cache on the host is queried first. 2. If there is no entry in the local cache, the local HOSTS file is queried next. 3. If there is no entry in the local HOSTS, the query is forwarded to any configured DNS servers on the host. If no DNS servers are configured, the query will fail. 4. If the configured DNS server is not authoritative for that domain, and does not have that DNS entry locally cached, the query will be forwarded up the DNS hierarchy. DNS servers can be configured with one or more forwarders. Organizations often point to their ISP’s DNS servers for DNS forwarding purposes. 5. If no forwarders are available, the query is forwarded to the Root DNS server(s), which will likely have the entry cached. 6. In the rare circumstance that the Root servers do not have a cached entry, the query will be forwarded back down the hierarchy to the authoritative DNS server for that domain. Dynamic DNS allows DNS to be integrated with Dynamic Host Configuration Protocol (DHCP). When DHCP hands out an IP address lease, it will automatically update the DNS entry for that host on the DNS server. * * * All original material copyright © 2013 by Aaron Balchunas (aaron@routeralley.com), unless otherwise noted. All other material copyright © of their respective owners. This material may be copied and used freely, but may not be altered or sold without the expressed written consent of the owner of the above copyright. Updated material may be found at http://www.routeralley.com.
Page 1 and 2:
CCNA Study Guide v2.62 - Aaron Balc
Page 3 and 4:
Page 5 and 6:
Page 7 and 8:
Page 9 and 10:
Page 11 and 12:
Page 13 and 14:
Page 15 and 16:
Page 17 and 18:
Page 19 and 20:
Page 21 and 22:
Page 23 and 24:
Page 25 and 26:
Page 27 and 28:
Page 29 and 30:
Page 31 and 32:
Page 33 and 34:
Page 35 and 36:
Page 37 and 38:
Page 39 and 40:
Page 41 and 42:
Page 43 and 44:
Page 45 and 46:
Page 47 and 48:
Page 49 and 50:
Page 51 and 52:
Page 53 and 54:
Page 55 and 56:
Page 57 and 58:
Page 59 and 60:
Page 61 and 62:
Page 63 and 64:
Page 65 and 66:
Page 67 and 68:
Page 69 and 70:
Page 71 and 72:
Page 73 and 74:
Page 75:
Page 78 and 79:
Page 80 and 81:
Page 82 and 83:
Page 84 and 85:
Page 86 and 87:
Page 88 and 89:
Page 90 and 91:
Page 92 and 93:
Page 94 and 95:
Page 96 and 97:
Page 98 and 99:
Page 100 and 101:
Page 102 and 103:
Page 104 and 105:
Page 106 and 107:
Page 108 and 109:
Page 110 and 111:
Page 112 and 113:
Page 114 and 115:
Page 116 and 117:
Page 118 and 119:
Page 120 and 121:
Page 122 and 123:
Page 124 and 125:
Page 126 and 127:
Page 128 and 129:
Page 130 and 131:
Page 132 and 133:
Page 134 and 135:
Page 136 and 137:
Page 138 and 139:
Page 140 and 141:
Page 142 and 143:
Page 144 and 145:
Page 146 and 147:
Page 148 and 149:
Page 150 and 151:
Page 152 and 153:
Page 154 and 155:
Page 156 and 157:
Page 158 and 159:
Page 160 and 161:
Page 162 and 163:
Page 164 and 165:
Page 166 and 167:
Page 168 and 169:
Page 170 and 171:
Page 172 and 173:
Page 174 and 175:
Page 176 and 177:
Page 178 and 179:
Page 180 and 181:
Page 182 and 183:
Page 184 and 185:
Page 186 and 187:
Page 188 and 189:
Page 190 and 191:
Page 192 and 193:
Page 194 and 195:
Page 196 and 197:
Page 198 and 199:
Page 200 and 201:
Page 202 and 203:
Page 204 and 205:
Page 206 and 207:
Page 208 and 209:
Page 210 and 211:
Page 212 and 213:
Page 214 and 215:
Page 216 and 217:
Page 218 and 219:
Page 220 and 221:
Page 222 and 223:
Page 224 and 225: CCNA Study Guide v2.62 - Aaron Balc
Page 304: CCNA Study Guide v2.62 - Aaron Balc
show all

Cisco CCNA Study Guide - Router Alley

Create successful ePaper yourself

Delete template?

Save as template?