I would like to configure a GRE tunnel interface between his CloudEngine CE6850-48S4Q-EI and CISCO 6509. I have L3 connectivity between the source and destination IP addresses but the tunnel interface is down on the CE.

Configuration on CE6850:

interface Tunnel0

mtu 1476

ip address 192.168.121.1 255.255.255.252

tunnel-protocol gre

source 10.163.50.14

destination 10.34.75.2

Configuration on CISCO 6509:

interface Tunnel0

ip address 192.168.121.2 255.255.255.252

tunnel source 10.34.75.2

tunnel destination 10.163.50.14

Check to tunnel and is down:

<SCC-Niciman-C01>dis int t0

Tunnel0 current state : DOWN (ifindex: 156)

Line protocol current state : DOWN

Description: ** Niciman VNOC Staff **

Route Port,The Maximum Transmit Unit is 1500, Current BW: 65.53Kbps

Internet Address is 10.255.255.1/30

Encapsulation is TUNNEL, loopback not set

Tunnel source 10.163.50.14 (Vlanif1073), destination 10.34.75.2

Tunnel protocol/transport GRE/IP, key disabled

keepalive enable period 10 retry-times 3

Checksumming of packets disabled

Current system time: 2017-08-08 09:45+01:00 DST

    300 seconds input rate 0 bits/sec, 0 packets/sec

    300 seconds output rate 0 bits/sec, 0 packets/sec

    0 seconds input rate 0 bits/sec, 0 packets/sec

    0 seconds output rate 0 bits/sec, 0 packets/sec

    0 packets input,  0 bytes

    0 input error

    0 packets output,  0 bytes

    0 output error

    Input:

      Unicast: 0 packets, Multicast: 0 packets

    Output:

      Unicast: 0 packets, Multicast: 0 packets

    Input bandwidth utilization  : --

    Output bandwidth utilization : --

I configured the keepalive to 10 seconds and retried but the interface tunnel status was still down.

On CISCO:

interface Tunnel0

keepalive 10 3

On CE:

interface Tunnel1

keepalive period 10

Then removed the MTU 1476 from the Cloud Engine and test again, the tunnel interface ststus was still down.

interface Tunnel0

undo mtu

Root cause: There is a software limitation for V100R003C00 version and a loopback eth-trunk must be configured for the GRE tunnel. After this version there is no need to configure the service type tunnel on the Eth-trunk interface.

The loopback eth-trunk must be configured for the GRE tunnel. Configure an eth-trunk for GRE tunnel (The eth-trunk must have some member ports but no need to connect the port.)

[~SwitchA] interface eth-trunk 1

[*SwitchA-Eth-Trunk1] service type tunnel

[*SwitchA-Eth-Trunk1] quit

Binding the eth-trunk to the tunnel.

[*SwitchC-Tunnel0] binding interface eth-trunk 1