HPE MSR3000 - Mgre Support for NAT Traversal; Mgre Configuration Task List

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An NHC-NHS tunnel is permanent. An NHC can establish permanent tunnels to any number of
NHSs.
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NHC-NHC tunnel establishment process:
a. In a full-mesh network, when an NHC receives a data packet but finds no tunnel for
forwarding the packet, the NHC (initiator) sends an address resolution request to the NHS.
b. After receiving the request, the NHS looks up the local NHRP mapping table to find the peer
NHC (responder) and forwards the request to the peer NHC.
c. After receiving the request, the peer NHC creates a temporary tunnel and sends an address
resolution response to the initiator.
An NHC-NHC tunnel is dynamic. If no data is exchanged within the NHC-NHC tunnel idle
timeout, the tunnel will be deleted.
Route learning and packet forwarding
mGRE nodes learn private routes by using dynamic routing protocols.
Dynamic routing must be configured for all private networks and mGRE tunnel interfaces to ensure
IP connectivity among the private networks. From the perspective of private networks, an mGRE
tunnel is a link that connects different private networks. A dynamic routing protocol discovers
neighbors and updates routes over mGRE tunnels, and establishes a routing table.
When an NHC receives a packet destined for a remote private network, it performs the following
operations:
1. Searches the routing table for the next hop address to the target private network.
2. Looks up the local NHRP mapping table to obtain the public address that corresponds to the
next hop address.
3. Uses the public address as the tunnel destination address to encapsulate the packet.
4. Sends the encapsulated packet to the peer NHC over the mGRE tunnel.
mGRE support for NAT traversal
An NHC-NHC tunnel can traverse a NAT gateway. The tunnel can be established when the tunnel
initiator, receiver, or both ends reside behind the NAT gateway.
mGRE configuration task list
To set up an mGRE network, first configure the NHSs and then the NHCs.
IMPORTANT:
The device can act only as an NHC. It cannot act as an NHS.
To configure mGRE on an NHC: