Will my AD Trust be affected by raising the forest level?

We have two different forests.

Forest 1 = domainA.local
Forest 2 = domainB.com

These are two separate forests but there is a trust between the two of them in order to allow access to certain systems and services on the domainB.com network.  There is also a Site to Site VPN between the two locations.  You can see the entire directory in the attached image.

domainB.com has all domain controllers with 2008 R2.  domainA.local has 2003 Domain Controllers.  The forest level of domainB.com has been left at 2003 due to not knowing if raising the forest level will affect the trust in any way.  

Is it safe to say I can raise the function level of the domainB.com trust to 2008 R2 without affecting the domainA.local domain.  I would like to take advantage of other features in a 2008 R2 domain level.  

Any assistance is appreciated.
Forest.jpg
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Shawn CøadySVP Information SystemsAsked:
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MaheshArchitectCommented:
I don't see any problems in raising functional level to 2008 R2
This is totally for internal AD configuration purpose and it decide which version of DC (2003 \ 2008 \ 2008 R2) can be placed in domain or forest. Also it will add new functionalities with AD.
It has nothing to do with trust. Trust will work as it is.
U already have 2003 functional levels.
https://social.technet.microsoft.com/Forums/windowsserver/en-US/9d127cd7-9d0a-4bbb-9586-014f46d004c6/risks-of-raising-domainforest-functional-level-from-2003-mixed-to-2008-native?forum=winserverDS

Only if you have any legacy application servers which are also integrated with active directory, just ensure that they are working with 2008 R2 active directory.
If they are working, raising functional levels will not make any difference
U might want to go through below links to understand other impacts if any

Check below link for possible impact
http://blogs.technet.com/b/askpfeplat/archive/2012/04/09/a-few-things-you-should-know-about-raising-the-dfl-and-or-ffl-to-windows-server-2008-r2.aspx
http://blogs.technet.com/b/askds/archive/2011/06/14/what-is-the-impact-of-upgrading-the-domain-or-forest-functional-level.aspx
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Shawn CøadySVP Information SystemsAuthor Commented:
Thanks for the insight and documentation.  I didn't think it would matter but thought I would confirm by ideas first.  I will still give your articles a read to see if there is any additional info I might want.  Again much appreciated.
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