Applying an ACL policy to a tunnel interface
device(config)# interface tunnel 1
device(config-tnif-1)# tunnel mode gre ip
device(config-tnif-1)# ip access-group 10 in
Configuring an IP address for a tunnel interface
An IP address sets a tunnel interface as an IP port and allows the configuration of Layer 3 protocols, such as OSPF, BGP, and Multicast
(PIM-DM and PIM-SM) on the port. Note that the subnet cannot overlap other subnets configured on other routing interfaces, and both
ends of the tunnel should be in the same subnet.
To configure an IP address for a specified tunnel interface, enter commands such as the following.
device(config)# interface tunnel 1
device(config-tnif-1)# ip address 10.10.3.1/24
Syntax:
[no] ip address
ip-address
The
ip-address
is the IP address being configured for the specified tunnel interface.
Configuring a static route to a tunnel destination
If a route to the tunnel destination does not already exist on the tunnel source, create a static route and set the route to go through the
tunnel interface.
device(config)# ip route 131.108.5.0/24 10.0.8.1
device(config)# ip route 10.10.2.0/24 tunnel 1
Syntax:
[no] ip route
ip-address
tunnel
tunnel-ID
•
The
ip-address
variable is the IP address of the tunnel interface.
•
The
tunnel-ID
variable is a valid tunnel number or name.
Changing the MTU value for a tunnel interface
For important configuration considerations regarding this feature, refer to
GRE MTU configuration considerations
on page 107.
You can set an MTU value for packets entering the tunnel. Packets that exceed either the default MTU value of 1476/9192 bytes (for
jumbo case) or the value that you set using this command, are fragmented and encapsulated with IP/GRE headers for transit through the
tunnel (if they do not have the DF bit set in the IP header). All fragments will carry the same DF bit as the incoming packet. Jumbo
packets are supported, although they may be fragmented based on the configured MTU value.
NOTE
For the SX-FI8GMR6, SX-FI2XGMR6, SX-FI624HF, SX-FI624C, SX-FI624P, and the SX-FI62XG modules, all fragments will
carry the same DF bit as the incoming packet. For the SX-FI-24GPP, SX-FI48GPP, SX-FI-24HF, SX-FI-2XG, and SX-FI-8XG
modules and the FCX modules, the DF bit on the outer IP header after encapsulation will be set if the PMTU is enabled. If
PMTU is disabled, the DF bit will be unset irrespective of the DF bit of the incoming packet.
The following command allows you to change the MTU value for packets transiting "tunnel 1":
device(config)# interface tunnel 1
device(config-tnif-1)# ip mtu 1200
Syntax:
ip mtu
packet-size
The
packet-size
variable specifies the maximum size in bytes for the packets transiting the tunnel. Enter a value from 576 through
1476. The default value is 1476.
IPv4 point-to-point GRE tunnels
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