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IPSec Manual and SPI question

Unanswered Question
Nov 14th, 2002
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Hi all,


We are impelementing IPSec manual site to site because other site doesn't

support IKE. I know that if you implement IPSec manual keying

-- ACL's for crypto map entries tagged as ipsec-manual are restricted to as

single permit entry and subsequent entries are ignored.

-- The SAs established by a manual crypto map entry are only for a single

data flow.


IKE doesn't have any restrictions like that. Is this because of IKE

automatically assigns SPI numbers to the other permit entries for the same

access-list. Or is there any other reason?


I know the solution for the IPSec manual restriction of permit entries. I

want to know why is this restriction. Because of one SPI for one permit

entry?


Any help will be really appreciated.


Best regards,

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gfullage Mon, 11/18/2002 - 19:56
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  • Cisco Employee,

Basically yes. Each line in your ACL actually builds a separate tunnel, with unique SPI's. If you use manual keys, you can only provide one set of SPI's, and therefore, the router/firewall can only build one tunnel, hence only one line in your ACL.


With IKE, it dynamically creates unique SPI's per tunnel/ACL line, and therefore you're not limited.

btimuralp Tue, 11/19/2002 - 00:46
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I was expecting this answer, thanks.


Best regards,

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