Cisco CCNA Study Guide - Router Alley

More documents

Recommendations

Info

CCNA Study Guide v2.62 – Aaron Balchunas 300 Section 27 - Network Address Translation - NAT (Network Address Translation) The rapid growth of the Internet resulted in a shortage of available IPv4 addresses. In response, a specific subset of the IPv4 address space was designated as private, to temporarily alleviate this problem. A public address can be routed on the Internet. Thus, devices that must be Internet-accessible must be configured with (or reachable by) public addresses. Allocation of public addresses is governed by the Internet Assigned Numbers Authority (IANA). A private address is intended for internal use within a home or organization, and can be freely used by anyone. However, private addresses can never be routed on the Internet. In fact, Internet routers are configured to immediately drop traffic with private addresses. Three private address ranges were defined in RFC 1918, one for each IPv4 class: • Class A - 10.x.x.x /8 • Class B - 172.16.x.x /12 • Class C - 192.168.x.x /24 It is possible to translate between private and public addresses, using Network Address Translation (NAT). NAT allows a host configured with a private address to be stamped with a public address, thus allowing that host to communicate across the Internet. It is also possible to translate multiple privately-addressed hosts to a single public address, which conserves the public address space. NAT provides an additional benefit – hiding the specific addresses and addressing structure of the internal (or private) network. Note: NAT is not restricted to private-to-public address translation, though that is the most common application. NAT can also perform public-to-public address translation, as well as private-to-private address translation. NAT is only a temporarily solution to the address shortage problem. IPv4 will eventually be replaced with IPv6, which supports a vast address space. Both Cisco IOS devices and PIX/ASA firewalls support NAT. * * * 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 301 Types of NAT NAT can be implemented using one of three methods: Static NAT – performs a static one-to-one translation between two addresses, or between a port on one address to a port on another address. Static NAT is most often used to assign a public address to a device behind a NAT-enabled firewall/router. Dynamic NAT – utilizes a pool of global addresses to dynamically translate the outbound traffic of clients behind a NAT-enabled device. NAT Overload or Port Address Translation (PAT) – translates the outbound traffic of clients to unique port numbers off of a single global address. PAT is necessary when the number of internal clients exceeds the available global addresses. NAT Terminology Specific terms are used to identify the various NAT addresses: • Inside Local – the specific IP address assigned to an inside host behind a NAT-enabled device (usually a private address). • Inside Global – the address that identifies an inside host to the outside world (usually a public address). Essentially, this is the dynamically or statically-assigned public address assigned to a private host. • Outside Global – the address assigned to an outside host (usually a public address). • Outside Local – the address that identifies an outside host to the inside network. Often, this is the same address as the Outside Global. However, it is occasionally necessary to translate an outside (usually public) address to an inside (usually private) address. For simplicity sake, it is generally acceptable to associate global addresses with public addresses, and local addresses with private addresses. However, remember that public-to-public and private-to-private translation is still possible. Inside hosts are within the local network, while outside hosts are external to the local network. * * * 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:
Page 226 and 227:
Page 228 and 229:
Page 230 and 231:
Page 232 and 233:
Page 234 and 235:
Page 236 and 237:
Page 238 and 239:
Page 240 and 241:
Page 242 and 243:
Page 244 and 245:
Page 246 and 247:
Page 248 and 249:
Page 250 and 251: CCNA Study Guide v2.62 - Aaron Balc
Page 304: CCNA Study Guide v2.62 - Aaron Balc
show all

Cisco CCNA Study Guide - Router Alley

You also want an ePaper? Increase the reach of your titles

Delete template?

Save as template?