04-16-2012 04:21 AM - edited 03-04-2019 04:02 PM
HI all
Why do people mainly use GRE tunnels ?
do they support broadcast and Multicast ?
cheers
04-16-2012 04:44 AM
Hi Carl,
Yes..it does support Multicast & broadcast support compared to traditional IPsec tunnels. Search in your favourite browser to gather more information on GRE tunnels and the purpose. Below is link from Cisco website for OSPF (Multicast) across GRE .
http://www.cisco.com/en/US/tech/tk583/tk372/technologies_configuration_example09186a00800a43f6.shtml
hth
MS
04-16-2012 05:06 AM
GRE Tunnels enable you to run routing protocols over the tunnels which makes it attractive.and routing protocols like ospf, eigrp, rip need multicast capability which the GRE tunnels provide.
However, gre tunnels add some over head of 24 bytes to your over all MTU.
There is something called "VTI" which is like GRE but not GRE. its a ipsec tunnel but you can run ur routing protocols on it. below is the link
HTH
Kishore
04-16-2012 05:27 AM
"However, gre tunnels add some over head of 24 bytes to your over all MTU."
28 bytes if you use "tunnel key"
04-16-2012 06:45 AM
hi there
So is a VTI not using GRE? Does it just use IPsec Tunnel mode ?
also is it not the same as a GRE over IPsec tunnel ?
cheers
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