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I want to ask whether it is possible to configure Layer 3 Tunnel with the two end points/interfaces have dynamic IP address?

If the interface IP change, the tunnel will have to be re-negotiated, is that right?

The two L3 Tunneling protocol I know are GRE and IPSec. GRE definitely need static IP. Does IPSec need static IP as well?

Thank you

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    A tunnel is really just sending packets between two hosts, and if the address of one of the hosts changes, the tunnel is broken. – Ron Maupin Mar 20 '18 at 1:19
  • The tunnel would break , yes. One solution might be to have a protocol propagate these changes in IP for you. While the tunnels might break, they would be renegotiated. Try looking up DMVPN(uses P2MP GRE with NHRP) – surya Mar 20 '18 at 5:25
  • Did any answer help you? If so, you should accept the answer so that the question doesn't keep popping up forever, looking for an answer. Alternatively, you could provide and accept your own answer. – Ron Maupin Apr 1 '18 at 22:53
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The short answer to answer your question is No. IPSEC needs at least one endpoint with a static IP.

The slightly longer answer is: I have seen at least one SOHO router that allowed you to specify a DNS entry as the endpoint, so if you find a router that has this feature you may be able to get around this limitation with a Dynamic DNS service to track at least on of the two dynamic IPs and map them to a resolvable hostname.

  • Thanks Benjamin. So how does IPSec tunnel remain reachable when one out of the two end points use dynamic IP? Its algorithm allow it to figure out the dynamic IP interface? – td16 Mar 23 '18 at 4:08
  • It's actually simpler than that - only the dynamic end initiates the connection. – Benjamin Dale Mar 26 '18 at 1:09
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If your equipment supports it, you can set up the tunnel endpoints by DNS name rather than IP address, and using some dynamic DNS service keep the names up to date when the addresses change. It can be made to work, but note that the failure modes are likely to be awful. (Might have to tune timeouts to detect the broken link.)

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Apart from dynamic dns as mentioned in the other answers, another technique is to use a 3rd device that both tunnel endpoints register with, and which informs the endpoints of the peer's address. E.g. in DMVPN the hub performs this role, in Viptela SEN (now Cisco SDWAN) the vSmart controller does.

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