01-03-2014 11:33 AM - edited 02-21-2020 07:25 PM
Hello,
I beleive normal IPSEC site-to-site VPN can accomodate data and voip traffic. But I have seen many implementations with IPSEC/GRE implementations for voice over VPN. Why is the need for GRE in this case?
Thank you.
01-03-2014 12:59 PM
GRE is typically used when multicast is needed across the tunnel, such as paging or MoH.
01-03-2014 01:39 PM
Good point raised by Collin.
GRE over IPsec allows you to have one tunnel (IPsec SA) for all traffic, classic IPsec would typically require multiple SAs.
On IOS, GRE allows tunnel protection which is simpler and recommended.
Apart from transporting multicast, GRE can carry any traffic on top IPv4, IPv6, IPX(?)...
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