Hello Brent,
why not just put another router between the POST router and your network?
Or connect the POST router to a dedicated network port of a linux "router"?
Best regards,
Michel
On 08/04/2019 16:46, Brent Frère wrote:
Let's say the firewall outside interface is
192.168.1.254/24. The general Internet access (vDSL modem) is 192.168.1.1/24, connected to
the firewall by Ethernet. It NATs all outgoing IP traffic to the Internet by replacing the
source IP address by its own public IP address (masquerading) to make it routable on the
World Wild Internet.
A new secondary Internet access is added. It is implemented by a Meraki, operated by
POST. I have NO ACCESS to its configuration, not even the pppoe credentials, so no ways to
circumvent it.
The Meraki LAN interface is, let's say, 192.168.1.100/24. It has a fixed public IPv4
WAN address. All incoming traffic (limited to IPv4, with a limited MTU and only ICMP, UDP
or TCP because of POST limitations) is forwarded to the firewall outside IP address,
192.168.1.254/24, by POST configuration.
This way, the general traffic works as usually and previously: through the general
Internet access, the default gateway, the vDSL modem. There is so in the firewall a
"default route" with 192.168.1.1 as default gateway.
Some selected traffic can be routed to the POST Internet access, depending on its
destination IP address or because of flagged traffic (iproute with marks and multiples
routing tables to select the appropriate gateway).
As example, all the traffic to youporn (216.18.168.116) could be routed through the POST
Internet access by adding a static route on the firewall:
# route add -host 216.18.168.116 gw 192.168.1.100
This traffic takes so the POST Internet access to reach its destination, and is NATed by
the Meraki (source IP address NAT), so the return traffic reaches back the POST Internet
access, and is reverse-NATed back to the firewall...
The problem is to try to _use the POST Internet access for INCOMING traffic_.
If a connection attempt comes from the Internet (let's say 1.1.1.1) through this
POST Internet access, the IP packet is forwarded to the firewall ("exposed
host") by the Meraki, because of POST configuration, and it is what is expected. But
as this packet has still 1.1.1.1 as source IP address, the answer to this request is
routed back to the Internet by the general Internet access, so will be NATed (masqueraded)
from a different public IP address.
The host 1.1.1.1 will then receive answer to it's connection attempt from a
completely different IP address, and so will not link it to the request, so it won't
work.
The solution would be to masquerade the source IP address of the incoming traffic
crossing the Meraki, so that the firewall would see it as coming from the Meraki internal
IP address, in this example 192.168.1.100/24.
The firewall will then answer the request apparently coming from 192.168.1.100, and the
Meraki should reverse-NAT it back to it's actual destination, in this example
1.1.1.1. The connection will establish.
For sure, I know that in this case, the firewall will not be able to filter incoming
traffic based on it's source IP address, but it's just about making it possible,
not (yet) clever or appropriate.
So I ask POST technical service to set-up this internal NAT, and they answer that
it's NOT SUPPORTED by the Meraki. I can't believe Cisco has became so bad that
they are not able to do this simple masquerading, especially as I suspect they use Linux
as underlying technology...
So I looked at Meraki documentation, but I didn't found anything else than a very
basic web-based configuration interface manual. That's why I ask if:
* Somebody knows Meraki
* Is Meraki based on Linux kernel ?
* Is there a way to access the Meraki CLI ?
* Is there a way to configure this very basic traffic masquerading rule ?
So that I could find a solution (at least limited so far) and learn POST help-desk again
something they didn't know...
Note: changing the default route IS NOT an acceptable solution, as changing the default
Internet access would have lots of other consequences, due to historical reasons.
The incoming traffic through the POST Internet access comes potentially from /any/ public
IPv4 routable address. It should be answered by the two Internet accesses.
Actually, the real situation is more complex: the firewall is exposed to incoming traffic
from already three Internet accesses, provided by various ISPs and technologies. And it
works, as I have control over those Internet accesses.
The problem occurs just because of this fourth "Internet access" by POST, which
is out of my control and apparently unable to provide this basic feature: masquerading the
incoming traffic.
By the way, I'm not even sure this "Internet access service" can be
qualified of "Internet access" as anybody knows (or should know) that what is
common on the Internet is... the IP protocol. However, this "Internet access"
service is strictly limited to IPv4, and to only the TCP, UDP and ICMP protocols. This is
so a very limited Internet access, somehow as you might have received from some hotels in
old times: a "Internet access" that was limited to web browsing, and blocked any
"unknown"
service, such as SSH, telnet, IMAP, and so on. This also happened in the very old days
(about 15 years ago) when some ISPs blocked SIP traffic or added intentionally jitter to
the VoIP audio streams...
Those limitations have been ruled as illegal already, but here in Luxembourg, there is a
delinquent company called POST that still apply such restrictions, apparently...
Practically, those restrictions prevents customers to access to:
* IPSec VPNs, as some implementations requires ESP and AH protocols (not TCP or UDP)
* GRE
* IPinIP
* PIM, IGMP (for multicast)
* various routing protocols
* IPv6
* RDP
* and so on...
which are _part of the Internet protocols_, even if unknown by POST commercial
management, apparently.
I notice that some other ISPs (LOL, MixVoIP, ...) do provide genuine Internet accesses,
with full 1500 MTU and all the services above IP, as expected...
Any help would be appreciated.
Le 08/04/2019 à 12:17, Gökdağ Göktepe a écrit :
I am trying to figure out your problem but French
is a bit complicated for me. As an instance I think it has sth to do with administrative
distance . But I don’t know if you have static routes defined for your secondary internet
access and how
Gökdağ
On 8 Apr 2019, at 11:56, Brent Frère <Brent.Frere(a)abilit.eu
<mailto:Brent.Frere@abilit.eu>> wrote:
> Not yet.
>
> Le 08/04/2019 à 11:17, Gökdağ Göktepe a écrit :
>> Hi Brent did you find any solution?
>>
>> Gökdağ
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