Secondary Interfaces

[ersofgeorgia]

I am looking to break up a flat network into separate subnets according to function. How many secondary IP addresses can be used on a routers ethernet interface?

[mahmoodmkl]

Hi

Will u be going to use vlans in this scenario.if yes then u can go ahead and use sub-interfaces instead of secondry address if u r router supports IP PLUS feature.

U can many secondry address not sure abt the number.

Thanks

Mahmood

[ersofgeorgia]

Thats a great Idea. I did not even think of going the sub interface route. That may be the answer I was seeking. I knew about them and have used them when dealing with Frame relay but did not think to use them for this.

-Joe

[ankbhasi]

Hi Friend,

The documents says unlimited number of secondary ip addresses can be defined on any interface but even if it is not unlimited it will support many which will definetely be more than your requirement.

However I will recommed you to have a look at this link for correct usage of secondary ip address

http://www.cisco.com/univercd/cc/td/doc/product/software/ios124/124tcr/tiad_r/adressht.htm#wp1135431

HTH

Ankur

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[ersofgeorgia]

I am looking to buy 2 2800 series routers with gigabit interfaces and use the secondary interface feature. Unfortunately the person before me purchased 3Com gig switches that do not have the ability for etherchannel that I have found. I also want to use HSRP to have redundancy failover so I am researching the use of HSRP on multiple subnets using secondary interfaces. I am trying to verify it can be done before I make the purchase. I appreciate the responses s far.

-Joe

[ankbhasi]

Hi Joe,

Yes HSRP can be configured with secondary ip addresses.

When you define the standby virtual ip address in HSRP for secondary address you will also get an option to configure "secondary" keyword which will define that standby virtual ip address for secondary ip address on your interface.

HTH

Ankur

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