Routes for a tunnel must be available on both the source
and destination devices so that packets encapsulated with GRE can
be forwarded correctly. A route passing through tunnel interfaces
can be a static route or a dynamic route.
Context
The routes passing through a tunnel must be available
on both the local and remote devices so that packets encapsulated
by GRE can be forwarded properly. These routes can be static routes
or dynamic routes. When configuring tunnel routes, note the following:
A static route must be configured on both the source and destination
devices if it is to be configured. The destination address of the
route is the destination address of the packet that is not encapsulated
by GRE, rather than the destination address of the tunnel or the peer
tunnel interface address. The outbound interface is the local tunnel
interface.
When configuring a dynamic routing protocol, enable the protocol
on both the tunnel interface and the physical interface connected
to the private network. When you configure a route to the remote end
of a tunnel, the next hop cannot be the address of the tunnel interface.
Otherwise, GRE encapsulated packets cannot be forwarded properly.
As shown in Figure 3-1, the
source interface of Tunnel1 is interface1 on DeviceA, and the destination physical interface of Tunnel1 is interface2
on DeviceC. When configuring a dynamic routing protocol, you need to enable
the protocol on both the tunnel interface and the interface connected
to the PC. In the routing table, the outbound interface for the route
to interface2 on DeviceC cannot be Tunnel1.
In practical configurations, different
routing protocols or different processes of the same routing protocol
need to be used for tunnel interfaces and public network physical
interfaces. This prevents a tunnel interface from being selected as
an outbound interface of routes to the destination of the tunnel.
In addition, this also ensures that users packets are forwarded through
the tunnel instead of the physical interface.
Figure 3-1 Diagram of configuring the GRE dynamic routing protocol
Interfaces 1 through 4 in this example
are GE 0/1/0, GE 0/2/0, Tunnel 1, and Tunnel 2, respectively.
Perform the following steps on the devices at two ends
of a tunnel.
Procedure
Run system-view
The system view is displayed.
Choose one of the following methods to configure routes
passing through the tunnel interface.
Run the ip route-static ip-address { mask | mask-length } tunnel interface-number [ description text ] command to configure a static route.
Configure dynamic routes using IGP or BGP. Details for the
procedure are not provided here. For the configuration of dynamic
routes, see the NE40E Configuration Guide - IP Routing.
Run commit
The configuration is committed.
Follow-up Procedure
To implement millisecond-level fault detection
for a GRE tunnel, configure the following BFD functions on the GRE
tunnel interface:
Configure dynamic BFD
for RIP
Configure BFD for OSPF
on a specified interface
Configure dynamic BFD
for IS-IS
(Optional) Configuring a TTL Processing Mode for a GRE Tunnel
To enable a GRE tunnel to process
TTLs carried in packets, configure the GRE tunnel to process these TTLs
in pipe or uniform mode.
Context
Perform the following steps on Routers at both ends of a GRE tunnel.
Procedure
Run system-view
The system view is displayed.
Run slot slot-id
The slot view is displayed.
Run gre ttl-mode { pipe | uniform }
A TTL processing mode is configured for the GRE tunnel.
Run commit
The configuration is committed.
You can get more help from following link:
https://support.huawei.com/enterprise/en/doc/EDOC1100125452/5f674fbf/configuring-a-gre-tunnel
I hope it helps.
