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GRE Tunnels

DANMOH009DANMOH009 Member Posts: 241
in CCNA & CCENT
I get that GRE tunnels are great for transferring routing protocols, as of the broadcast/multicast feature. Was wondering what else they are used for in the real world. Has anyone got any real life examples that will just help me clarify?

Thanks

Dan
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    networker050184networker050184 Mod Posts: 11,962 Mod
    They are used when you need to encapsulate something and send it across a network where the actual IP headers can not be used.

    Traffic across the internet, multicast across a non native multicast network, DMVPN etc.
    An expert is a man who has made all the mistakes which can be made.
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    DANMOH009DANMOH009 Member Posts: 241
    Can you create a GRE tunnel between 2 switches? or is that a stupid question.
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    networker050184networker050184 Mod Posts: 11,962 Mod
    You need to route traffic through the tunnel. So it depends on the switch really. Only the very high end switches support them as far as I know.
    An expert is a man who has made all the mistakes which can be made.
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    DANMOH009DANMOH009 Member Posts: 241
    Cool, Thanks Networker. Knew i could count on your response icon_smile.gif
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    powmiapowmia Users Awaiting Email Confirmation Posts: 322
    Cisco 3750 supports GRE tunnels... so even the low end switches can do it. It's the majority of tunnel types and features that are limited to routers/high end switches. For example, you can use a 3750 to route multicast, or OSPF/EIGRP over a GRE tunnel to extent you routing domain. If you want to encrypt the tunnel or do something like MPLSoGRE, you'll need an actual routing platform.
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