no auto summary

[carl_townshend]

when I use this command on my router, say I am advertising a 10.1.0.0/16 network, will other routers see it as 10.0.0.0/8 ?

[stephtchoko]

no auto summary is used with only RIP, EIGRP and IGRPP router.

>if you are using rip version 1(classful protocol), it can't adverstise a subnet mask in the routing.

>if you are using rip version 2 or eigrp (classless protocol), the router will advertise the subnet at classfull boudary.

But with eigrp, you can summarize manually on interface.

Please don't forget to rate this post.

Regards.

[carl_townshend]

Hi there I will be using eigrp on this router, can you tell me what this will be advertising to my other networks ? will it be 10/8

[ankurbhasin]

Hi Carl,

Nice to see that you have started appreciating and rating all the posts.

If you are using EIGRP, bydefault auto summarisation is enable so it will advertise as /8 but if you issue a command "no auto summary" under eigrp process it will advertise as /16.

Have a look at this link for clear understanding with topolgy and example for auto summarisation

http://www.cisco.com/warp/customer/103/eigrp-toc.html#auto

HTH, if yes please rate the post.

Ankur

[carl_townshend]

Hi Ankur

I cant open the doc, thanks, if I advertise a 10.1/16 address on my router and use no auto-sum on that router, another router has learnt this subnet but has auto sum switch on, would the router after that just see the 10/8 because it has auto sum on ?

[ankurbhasin]

Hi Carl,

EIGRP performs an auto-summarization each time it crosses a border between two different major networks.

So answer to your question is YES the router after that where auto summary is not diabled will advertise it as 10/8.

Try to open the link again as I made it public link now

http://www.cisco.com/warp/public/103/eigrp-toc.html#auto

HTH, if yes please rate all post.

Ankur