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How to add two IP in one interface

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Hi everybody,

I have a problem from the last 3 weeks that I cannot resolve. I want to configure a NAT rule to redirect all IPSec traffic from a external device to my internal device (it is not a CP device).

The problem is that I have configured a NAT rule and PING packets arrives correctly to internal device (NAT configuration works). When IPSec is sended instead of PING traffic the CheckPoint device does not redirect the packets (but I can see them with arriving to CP device). So it seems CheckPoint catch all IPSec traffic.

Is it possible to redirect IPSec traffic in a CP device? How can I do that? I have a r80.10 in clusterXL (I think IP aliases are not allowed in clusterXL..).

Thanks beforehand,

Mike.

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Re: How to add two IP in one interface

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Maybe i don't understand your initial issue.

As i understood, you want to establish a VPN between an external VPN Gateway and an internal device.
So we suggested to use a unused external IP address which is not configured as physical node IP nor as cluster IP on the checkpoint. This is to avoid the checkpoint assuming that received IKE/IPSec packets are directed at the checkpoint device.
If i am right with my assumption about your ycenario then you

first create a host object using the unused external IP, lets call it host-nat. Original object is called host.
So you create a static nat rule like this
Original Source: any
Original Destination: host-nat
Original Service: any

Translated Source: Original

Translated Destination: host (static)
Translated Services: original
Install on: <policy target>
Next you configure a rule from any (or internal net/Group negated) to host-nat Service IKE/IPSec and from host to any (instead of any, you may as well use an object representing the external vpn device) next you configure the mentioned proxy arp at gaia level.

If i am wrong or something missing, any CheckMate may correct me, it's long ago i really configured that last time Smiley Happy

best regards

Vincent

and now to something completely different
23 Replies

Re: How to add two IP in one interface

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Hi Mike,

Why don't you use NAT traversal?

Even if you successfully manage to NAT the traffic to the "inside" VPN device, without NAT traversal I think you will have issues because of the phase 1 ID mismatch.

Regards,

Bence

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Re: How to add two IP in one interface

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Hi Bence,
first of all thanks for your answer. Internal device is a FortiGate device and I have the Nat Transversal option marked (I see UDP packets).

Regards,

Mike.

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Re: How to add two IP in one interface

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I would let TAC resolve this, looks like too many unknowns are involved here.

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Re: How to add two IP in one interface

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Yes, I have a ticket opened with CheckPoint but in this three last weeks they don't give me any solution. May some user know somwthing..

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Re: How to add two IP in one interface

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I beg your pardon, but i can not imagine that, with so few information given, anyone could provide help 😞

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Re: How to add two IP in one interface

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I think you don't need extra information to answer this: How to configure NAT rule to redirect IPSec traffic in r80.10. ClusterXL.

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Re: How to add two IP in one interface

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Configure an unused static NAT using a different external IP than physical IP addresses of cluster nodes or cluster IP. Then the CP should not catch the IKE/IPSec traffic.

and now to something completely different
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Highlighted

Re: How to add two IP in one interface

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Hi Vincent,

thanks for your answer. I think this is the right solution but, How can use a different external IP? I mean, the rest of IPs of the IP pool don't response and IP aliasing (to add multiple IP to the same interface) is not allowed in clusterXL.

Thanks,

Mike.

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Re: How to add two IP in one interface

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This is the right place to use Proxy ARP on the external interface.

Configuring Proxy ARP for Manual NAT 

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Re: How to add two IP in one interface

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Hi Miguel,

not an IP which is configured at an Interface, just a "normal" IP used in Network object for static NAT.

And if needed,proxy arp in gaia

best regards

Vincent

and now to something completely different
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Re: How to add two IP in one interface

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Hi Vincent,

thanks for your answer. I tried it but it didn't work. Currently my ClusterXL has 3 IP addresses: one for VIP and two for cluster members. CP device only reply traffic where it destination is one of these three IP addresses, so I have to configure CP to attend another public IP too.

Thanks,

Mike.

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Re: How to add two IP in one interface

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Hi Miguel,

If I understand correctly you  have a device behind your FW that you want to terminate IPsec.

a) Your FW external interface needs to get the request destined for the device behind it (Another IP address, i.e IP2.

b) As suggested by Vincent configuring proxy arp, you FW will pickup those requests for IP2.

c) Create an object for this external IP (IP2)

d) Create a rule destined for this external IP (IP2) to allow IPsec traffic

e) On the object of your internal device (Fortigate), on NAT create a Static NAT with the IP of the external Interface (IP2).

Thanks,

Charris Lappas

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Re: How to add two IP in one interface

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OK my explanation was bit short, sorry

and now to something completely different
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Re: How to add two IP in one interface

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Hi Charris,

first of all thanks for your answer. I think proxy arp is not needed in my environment because traffic will be dispatched to the public IP of my CheckPoint. Internal device has only private addresses.

I have to configure CP to attend another public IP because the device doesn't redirect IPSec traffic if it is dispatched to current IPs.

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Re: How to add two IP in one interface

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Hello Miguel,

maybe you misunderstood me and Charris.
Regarding Proxy Arp.

When a packet arrives at your next hop (your Internet router), the router first sends an arp request to its Interface wich it choses by its Routing table. This arp request, asking for a mac address of the destination IP of the arriving packet is received by the Checkpoint.
Unless it's not done automatically, the proxy arp setting tells the Checkpoint to Reply to the arp request by sending the mac of the configured Interface.
Then the router receives this reply, adds the CP to his arp table and sends out the packet to the Checkpoint Interface.
Now the Checkpoint begins sending the packet through its chain.

best regards

Vincent

and now to something completely different
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Re: How to add two IP in one interface

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Hi Vincent,

thanks again for your answer. I think I understand it. Proxy arp is to reply arp request with your mac when arp request is not requesting for your ip. Packets are dispatched to CheckPoint address, not to internal device, so CP doesn't have to be configured proxy arp because IP destination is the CheckPoint address, not internal device address.

Is that correct? If not, I am misunderstanding you.

Thanks,

Miguel.

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Re: How to add two IP in one interface

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Maybe i don't understand your initial issue.

As i understood, you want to establish a VPN between an external VPN Gateway and an internal device.
So we suggested to use a unused external IP address which is not configured as physical node IP nor as cluster IP on the checkpoint. This is to avoid the checkpoint assuming that received IKE/IPSec packets are directed at the checkpoint device.
If i am right with my assumption about your ycenario then you

first create a host object using the unused external IP, lets call it host-nat. Original object is called host.
So you create a static nat rule like this
Original Source: any
Original Destination: host-nat
Original Service: any

Translated Source: Original

Translated Destination: host (static)
Translated Services: original
Install on: <policy target>
Next you configure a rule from any (or internal net/Group negated) to host-nat Service IKE/IPSec and from host to any (instead of any, you may as well use an object representing the external vpn device) next you configure the mentioned proxy arp at gaia level.

If i am wrong or something missing, any CheckMate may correct me, it's long ago i really configured that last time Smiley Happy

best regards

Vincent

and now to something completely different

Re: How to add two IP in one interface

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My configuration (and my issue) is what you explain but I didn't configure any proxy arp because, as you say, traffic is dispatched to CheckPoint (host-nat), not to host. It means router is asking for the host-nat's MAC, not for the mac of the internal device.


Up to this point NAT rule and security policies are configured, but I don't know why CP is going to catch packets with a different IP than IPs it has configures. Should it?

Thanks,

Miguel.

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Re: How to add two IP in one interface

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as the ip host-nat is just an Network object (host), you have to add Proxy arp leading to the external Interface of the checkpoint

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Re: How to add two IP in one interface

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Hi Vincent,

you are right. I read about proxy arp but with a different point of view and I got confused with that. This solution solve my problem!

Thanks for your help:)

Regards.

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Re: How to add two IP in one interface

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if I understand correctly, the topology is as the following  

Fortigate----------Checkpoint GW------------Internet --------------peer

You want to build the tunnel between Fortigate and the peer through checkpoint firewall. The first question is IPSEC blade enabled on checkpoint firewall (if yes, you need another public IP to terminate the tunnel on because checkpoint firewall is listening on ports udp 500 and udp4500, it is expecting to form vpn) in this scenario you need to get another public IP and statically NAT the Fortigate firewall behind it.

If IPsec blade not enabled on checkpoint firewall you might create manual NAT rules for the ports udp 500, 4500 to forward them to Fortigate and this might work.

Thanks  

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Re: How to add two IP in one interface

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Hi Houssameddine,

IPSec was enabled yes. Thanks for your answer. Proxy arp was the solution to this issue.

Regards.

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Re: How to add two IP in one interface

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I'm Glad you fixed the problem. I wanted to clarify more,

1- If you have an IPsec enabled on the checkpoint you will not be able to use the public IP of checkpoint to terminate the vpn on the internal fortigate firewall, because checkpoint listenning on the vpn ports and it thinks all vpn traffic is directed to it.

2-  The proxy arp configuration (Proxy arp is an arp reply without a request). you needed this configuration because you use manual static NAT to another public ip doesn't belong to checkpoint firewall and the upstream router doesn't know  how to reach the new public IP because it doesn't know the Mac address. If you used automatic static NAT for the new public IP you don't need to use proxy arp configuration.beside the NAT you need Firewall rules on the checkpoint firewall to allow IKE, ISAKMP and ESP or NAT-T to go pass through to the internal device.

Thanks

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