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Understanding the network.pdf - Back to Home

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172.16.2.0 /25<br />

172.16.2.128 /26 or 255.255.255.192<br />

172.16.2.192 /27 or 255.255.255.224<br />

172.16.2.224 /28 or 255.255.255.240<br />

172.16.2.240 /28 or 255.255.255.240<br />

172.16.2.248 /30 or 255.255.255.240<br />

172.16.2.252 /30 or 255.255.255.240<br />

The /25 segment could be used for <strong>the</strong> LAN, and ei<strong>the</strong>r of <strong>the</strong> /30<br />

spaces could be used for <strong>the</strong> WAN link addressing. WidgetCo also<br />

plans <strong>to</strong> provide dial-in access at <strong>the</strong> Concord office, so one of <strong>the</strong> /28<br />

spaces could be used for dial-in address allocation, leaving Concord<br />

with plenty of addresses <strong>to</strong> add additional <strong>network</strong>s in <strong>the</strong> future.<br />

The second option is <strong>to</strong> use on <strong>the</strong> WAN interfaces.<br />

The IOS option allows an interface <strong>to</strong> share <strong>the</strong> IP<br />

address of ano<strong>the</strong>r interface. This effectively creates a virtual bridge,<br />

whereby <strong>the</strong> LAN interfaces appear <strong>to</strong> be directly connected <strong>to</strong> one<br />

ano<strong>the</strong>r. Because <strong>the</strong> serial interfaces are borrowing <strong>the</strong> IP addresses<br />

of <strong>the</strong>ir reference interfaces <strong>to</strong> exchange IP datagrams, this method is<br />

only practical for point-<strong>to</strong>-point serial links.<br />

Both of <strong>the</strong>se approaches have limitations. The subnetting option<br />

segments <strong>the</strong> address space in<strong>to</strong> spaces that may not have practical<br />

use, especially if <strong>the</strong> LAN segments have enough hosts <strong>to</strong> utilize <strong>the</strong><br />

larger address spaces. The unnumbered option can present problems<br />

with certain IP routing pro<strong>to</strong>cols. The unnumbered interface is not<br />

accessible with Telnet using a VTY line or directly moni<strong>to</strong>rable with<br />

SNMP as <strong>the</strong> interface has no IP address.<br />

As it turns out, <strong>the</strong> Concord office is quite large so <br />

is a better option. Now let's examine <strong>the</strong> LAN and WAN interface<br />

configurations for <strong>the</strong> Concord and Ridgefield offices.<br />

The Concord side:

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