Dhcp IP via GRE Tunnel

[taimoor4engg]

Hey Guys,

I have a question regarding the GRE Tunnel, simple GRE usually works for me but this time I have different requirements.

We have 100 users in Australia, they would like to use my network in USA. so I define GRE Tunnel which is working fine but they want IP assigned via DHCP.

Current Config:

interface Tunnel101
 description GRE Tunnel to Aus
 ip address 192.168.60.21 255.255.255.252
 keepalive 10 2
 tunnel source 10.159.7.8
 tunnel destination 10.90.6.6

User in Australia wants DHCP scope should be 10.89.2.0/24, now I would like to know who do I do that, this is router so I have no option for VLAN.

Any help will be appreciated.

Thanks

[paul driver]

Hello

How are these clients obtaining their addressing at present?

res

Paul

[Richard Burts · Accepted solution]

I have not implemented this particular set of functions but it should work ok. You have showed us one tunnel configuration and I assume that this is probably your end of the tunnel. Is that correct? Is the other end of the tunnel configured in a similar way?  Am I correct in assuming that the site in Australia has a LAN which somehow connects to a router which has the GRE tunnel that connects to you? And I assume that you have a DHCP server available which can be used for this. Is that correct? And I assume that using  10.89.2.0/24  for Australia does not overlap any addressing that you use or cause any other problems for you. Is that correct?

Here is what I am thinking that you need to do for this to work:

- on your DHCP server you need to configure an appropriate scope for 10.89.2.0/24.

- you need to provide routing logic in your network that will reach 10.89.2.0/24 via this GRE tunnel. In an ideal situation I would think that you would run a dynamic routing protocol over the GRE tunnel that would advertise 10.89.2.0/24 to your network and you would advertise your networks to them over the tunnel.

- on the Australia router they need to configure an interface with an IP address in subnet 10.89.2.0/24.

- and on that interface they need to configure an ip helper-address that points to your DHCP server.

- on the Australia router they need to have routing logic that makes your DHCP server address reachable via the GRE tunnel.

- if the Australia site does not have subnet 10.89.2.0/24 as a connected interface on the router but is connected to something that connects to their router then it probably is still possible but it becomes more complex. So we will not discuss that possibility unless we need to.

HTH

Rick

[taimoor4engg]

This sounds very interesting to me but still have one question, in Australia side they use NATing so instead of configuring 10.89.2.0/24 on interface they could point internal scope to 10.89.2.0/24 and apply into the tunnel. what do you think .

[Richard Burts]

Perhaps I am not understanding something in your question or perhaps you did not fully understand my suggestion. How will Australia hosts use addresses in 10.89.2.0 if there is not some router interface configured with an address in that subnet?

I am also a bit puzzled about the use of NAT in Australia. Are you suggesting that the addresses will be translated as it goes through the tunnel? I can certainly understand that they might do address translation as their traffic goes out to the Internet. But I do not understand how (or why) they would translate traffic going to you through the tunnel.

HTH

Rick

[taimoor4engg]

This is a new design

[jason.loera]

You can configure your router to hand out DHCP addresses. Check this document out.

http://www.cisco.com/c/en/us/td/docs/ios/12_2/ip/configuration/guide/fipr_c/1cfdhcp.html