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The IP Tunnel - GRE Key Entropy Support feature enables load balancing of tunnel packets in the Generic Routing Encapsulation (GRE) mode of a core network.
You can enable tunnel entropy calculation only on Generic Routing Encapsulation (GRE) mode of the tunnel interface.
You must configure the tunnel key value before you enable tunnel entropy calculation.
You must not configure a tunnel key with a value that is more than 24 bits. The configuration of tunnel entropy calculation fails if the tunnel key value is more than 24 bits.
You cannot disable tunnel entropy calculation unless you remove the configured tunnel key.
The IP Tunnel - GRE Key Entropy Support feature enables load balancing of tunnel packets in the Generic Routing Encapsulation (GRE) mode of a core network. You can configure the tunnel entropy calculation feature only on the GRE mode of the tunnel interface.
In order to configure tunnel entropy calculation using the tunnel entropy command, you must first configure a tunnel key using the tunnel key command in interface configuration mode. The tunnel key has a maximum size of 32 bits. If you configure tunnel entropy calculation, 24 bits are reserved for the GRE key and 8 bits for entropy.
 Note |
If you configure a GRE tunnel key of 32 bits, you cannot configure tunnel entropy calculation. You must remove the tunnel key and then configure a key of the size of 24 bits or less. To disable an already configured GRE tunnel entropy, remove the GRE tunnel key value first. |
Entropy bits are calculated by 6 tuples, which are virtual routing and forwarding (VRF) ID, source IP address, destination IP address, source port, destination port, and protocols of the private IPv4/IPv6 packets in a network.
Perform this task to configure GRE tunnel entropy calculation:
| Command or Action | Purpose | |
|---|---|---|
| Step 1 |
enable Example: |
Enables privileged EXEC mode.
|
| Step 2 |
configure terminal Example: |
Enters global configuration mode. |
| Step 3 |
interface tunnel tunnel-number Example: |
Specifies a tunnel interface and number, and enters interface configuration mode. |
| Step 4 |
tunnel source {ipv4-addr | ipv6-addr | interface-type interface-number | dynamic} Example: |
Specifies the source IP address for a tunnel interface. |
| Step 5 |
tunnel destination {ipv4-addr | ipv6-addr | hostname | dynamic} Example: |
Specifies the destination IP address for a tunnel interface. |
| Step 6 |
tunnel mode gre ip Example: |
Configures the encapsulation mode for a tunnel interface. |
| Step 7 |
tunnel key key-number Example: |
Enables an ID key for a tunnel interface. |
| Step 8 |
tunnel entropy Example: |
Achieves load balancing of tunnel packets in a network. |
| Step 9 |
end Example: |
Returns to privileged EXEC mode. |
| Step 10 |
show interfaces interface-type interface-number Example: |
Displays statistics for all interfaces configured on a device or access server. |
The following example shows how to configure tunnel entropy calculation for GRE mode of the tunnel interface:
Device> enable
Device# configure terminal
Device(config)# interface tunnel 21
Device(config-if)# tunnel source 10.1.1.1
Device(config-if)# tunnel destination 172.168.2.1
Device(config-if)# tunnel mode gre ip
Device(config-if)# tunnel key 4683
Device(config-if)# tunnel entropy
Device(config-if)# end
The following is sample output from the show interfaces tunnel command, which displays that tunnel entropy calculation is enabled with a 24-bit key:
Device# show interfaces tunnel 21
Tunnel21 is up, line protocol is up
Hardware is Tunnel
MTU 17864 bytes, BW 100 Kbit/sec, DLY 50000 usec,
reliability 255/255, txload 1/255, rxload 1/255
Encapsulation TUNNEL, loopback not set
Keepalive not set
Tunnel source 10.1.1.1, destination 172.168.2.1
Tunnel protocol/transport GRE/IP
Key 0x124B, sequencing disabled
Checksumming of packets disabled
Tunnel Entropy Calculation Enabled (24-bit Key)
Tunnel TTL 255, Fast tunneling enabled
Tunnel transport MTU 1472 bytes
Tunnel transmit bandwidth 8000 (kbps)
Tunnel receive bandwidth 8000 (kbps)
Last input never, output never, output hang never
Last clearing of "show interface" counters 00:03:07
Input queue: 0/375/0/0 (size/max/drops/flushes); Total output drops: 0
Queueing strategy: fifo
Output queue: 0/0 (size/max)
5 minute input rate 0 bits/sec, 0 packets/sec
5 minute output rate 0 bits/sec, 0 packets/sec
0 packets input, 0 bytes, 0 no buffer
Received 0 broadcasts (0 IP multicasts)
0 runts, 0 giants, 0 throttles
0 input errors, 0 CRC, 0 frame, 0 overrun, 0 ignored, 0 abort
0 packets output, 0 bytes, 0 underruns
0 output errors, 0 collisions, 0 interface resets
0 unknown protocol drops
0 output buffer failures, 0 output buffers swapped out
| Related Topic | Document Title |
|---|---|
| Cisco IOS commands | Cisco IOS Master Command List, All Releases |
| Tunnel commands: complete command syntax, command mode, defaults, command history, usage guidelines, and examples | Cisco IOS Interface and Hardware Component Command Reference |
| Cisco IOS XE Interface and Hardware Component configuration modules |
Cisco IOS XE Interface and Hardware Component Configuration Guide |
| RFC | Title |
|---|---|
|
RFC6790 |
The Use of Entropy Labels in MPLS Forwarding |
| Description | Link |
|---|---|
|
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http://www.cisco.com/support |
The following table provides release information about the feature or features described in this module. This table lists only the software release that introduced support for a given feature in a given software release train. Unless noted otherwise, subsequent releases of that software release train also support that feature.
Use Cisco Feature Navigator to find information about platform support and Cisco software image support. To access Cisco Feature Navigator, go to www.cisco.com/go/cfn. An account on Cisco.com is not required.|
Feature Name |
Releases |
Feature Information |
|---|---|---|
|
IP Tunnel - GRE Key Entropy Support |
Cisco IOS XE Release 3.11S |
The IP Tunnel - GRE Key Entropy Support feature enables load balancing of tunnel packets in the Generic Routing Encapsulation (GRE) mode of a core network. The following commands were introduced or modified: tunnel entropy tunnel key show interfaces |
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