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Multiple GRE Tunnels

Robert Craig
Level 3
Level 3

I am trying to setup two different GRE multipoint tunnels. Tu0 is a regular GRE Multipoint with no IPSEC profile. Works like a charm. Now, I created another tunnel, Tu1 with the same configuration, except I changed the subnet of Tu1 to something different, changed the network-id, and also added an IPSEC profile (tunnel protection). As soon as I turn on Tu1, it kills all of the traffic terminating on Tu0 and I see errors about 'received unencrypted packet' and stuff. It's almost like the traffic starts heading towards Tu1 when it's on. Any ideas? Config is below if it helps. Thanks for any help.

interface Tunnel0

bandwidth 100000

bandwidth inherit

ip address 10.1.1.1 255.255.255.0

no ip redirects

ip mtu 1500

ip nhrp map multicast dynamic

ip nhrp network-id 1011

ip nhrp holdtime 600

ip nhrp registration timeout 30

ip tcp adjust-mss 1400

load-interval 30

qos pre-classify

tunnel source FastEthernet0/0

tunnel mode gre multipoint

tunnel bandwidth transmit 100000

tunnel bandwidth receive 100000

interface Tunnel1

bandwidth 100000

bandwidth inherit

ip address 10.1.2.1 255.255.255.0

no ip redirects

ip mtu 1500

ip nhrp map multicast dynamic

ip nhrp network-id 1012

ip nhrp holdtime 600

ip nhrp registration timeout 30

ip tcp adjust-mss 1400

load-interval 30

shutdown

qos pre-classify

tunnel source FastEthernet0/0

tunnel mode gre multipoint

tunnel bandwidth transmit 100000

tunnel bandwidth receive 100000

tunnel protection ipsec profile DMVPN


15 Replies 15

It is dependant on the hardware so it can vary.  But in some cases you can go past the "limit" (theoretically) if you do not have many routes per VRF.  But it is always best practice to stay within the limit of what your appliance is capable of.

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