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GRE Protocol Interface
How GRE Interface Support Works
The GRE interface provides two types of data processing; one for ingress packets and another for egress packets.
Ingress Packet Processing on GRE Interface
Figure given below provides a flow of process for incoming packets on GRE interface.
Note that in case the received packet is a GRE keep-alive or a ping packet then the outer IPV4 and GRE header are not
stripped off (or get reattached), but instead the packet is forwarded as is to the VPN manager or kernel respectively. In
case of all other GRE tunneled packets the IPV4 and GRE header are stripped off before sending the packet for a new
flow lookup.
Cisco ASR 5x00 Packet Data Network Gateway Administration Guide ▄
How GRE Interface Support Works ▀
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