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Secondary IP addressing

Answered Question
Nov 18th, 2002
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Is adding a second IP address to a router with only one ethernet interface the best solution when more IP addresses are needed on a LAN and the other subnet being used has had all the IP addresses exhausted? Will there be a performance issue if I add 12 more hosts from a different subnet on the same switch where there are 35 other hosts from another subnet within the same VLAN? I cannot use subinterfaces and ISL trunking since the ethernet interface is not a fastethernet interface.


Thanks,

RJ

Correct Answer by thisisshanky about 14 years 9 months ago

Since you dont have a fast ethernet interface, the only option you have is to use secondary ip addresses.


Adding 1 more subnet to the router ethernet interface as secondary shouldnt be a problem.


One thing to be noticed is that, the bandwidth of the link between the switch and the router will be shared with 12 more additional hosts, during communication between the 2 subnets. ( this case arises when all hosts are communicating simult., which is less likely).


Obviously there is a small percentage of load on the router, because it has to route more packets, not only to the wan, but also between the subnets.



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Correct Answer
thisisshanky Mon, 11/18/2002 - 18:33
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Since you dont have a fast ethernet interface, the only option you have is to use secondary ip addresses.


Adding 1 more subnet to the router ethernet interface as secondary shouldnt be a problem.


One thing to be noticed is that, the bandwidth of the link between the switch and the router will be shared with 12 more additional hosts, during communication between the 2 subnets. ( this case arises when all hosts are communicating simult., which is less likely).


Obviously there is a small percentage of load on the router, because it has to route more packets, not only to the wan, but also between the subnets.



jeffrey.zhou Wed, 11/20/2002 - 01:07
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In some higher IOS version, you can configure the ethernet to trunk dot1q. I ever test the configuration, and it work well.

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