Brocade Communications Systems ICX 7250 Series Configuration Manual page 90

IPv4 point-to-point GRE tunnels
To configure a tunnel loopback port, enter commands such as the following:
device(config)# interface tunnel 1
device(config-tnif-1)# tunnel loopback 1/3/1
Syntax: [no] tunnel loopback unit / slot / port
The unit / slot / port parameter identifies the tunnel loopback port for the specified tunnel interface, for example, 1/3/1.
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
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.
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.
90
GRE MTU configuration considerations
Brocade FastIron Layer 3 Routing Configuration Guide
on page 86.
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