"IP passthrough" for cellular/dialer connection

[Laz Peterson]

Hello there community,

I really don't know how to approach this, but I am trying to achieve an "IP passthrough" type of functionality from our 2901 with EHWIC-4G-LTE-V to our 7201.

Our Verizon account has a single static IP, and we have no problems setting up the dialer, connecting, or using the 2901+LTE for inside clients to reach the internet.

Since we have many VPN connections and no hardware encryption on the 2901, we want to use our 7201 with SA-VAM2+ for all of the communications, but the 2901 simply for its ability to use the LTE.  (When using the 2901 for our VPN connections, the CPU is so burdened that it very seriously affects the networking performance, even just LAN to router.)

The functionality we are trying to achieve would be similar to a CradlePoint that connects to the Verizon network, and then hands the static IP address over using DHCP.  In one of our locations, we have it setup this way.  Let's say the static IP is "166.60.60.153", then the result is a DHCP lease on the non-CradlePoint router at 166.60.60.153 with a subnet mask of 255.255.255.252 and gateway of 166.60.60.154.

I have tried setting up a transparent bridge, but the only documentation I can find is for PPPoE connections.  And nothing I have tried works.  All I want to do is pass our external static IP through the 2901 on to the 7201 router, and give it the static IP on one of its Ethernet interfaces so that it can maintain all of the VPN and failover routes.

Is this even possible?  If so, what type of configuration should I be looking at?

I have tried all sorts of bridge configurations with "bridge irb" and "no ip routing", while also setting "bridge 1 route ip" and setting "no dialer-list 1 protocol ip permit" with "dialer-list 1 protocol bridge permit", but also "dialer-list 1 protocol ip permit" and "dialer-list 1 protocol bridge permit".  And adding Dialer0 and GigabitEthernet0/0 to the bridge group.  Needless to say, I'm a little lost -- but would like to know whether or not this is even possible before I invest too much more time into it.

Any help would be greatly appreciated.  Thank you all.

~Laz Peterson

[BrianSekleckiGE]

I’ve been wondering for a while if anyone made this function work in IOS/XE.  Similar to Netgear LB2120 (Cradlepoint alternative)

[Georg Pauwen]

Hello,

the original post did not get a single reply...which does not necessarily mean that this functionality cannot be achieved. I looked at the CradlePoint and alsi the Netgear LB2120 you mentioned, and just for my understanding: these devices get a public IP address, and you want this (the same) IP address to be used by another device (router) connected to the CradlePoint/Netgear ?

[paul driver]

Hello

IOS bridging should indeed work, unless you are inadvertently trying to route instead, Just to confirm-.

bridge irb
bridge 1 protocol ieee
bridge 1 bridge ip

int x/x
bridge-group 1

[BrianSekleckiGE]

I haven't personally tried it, but some have reported failure making IRB/CRB work as you describe.

In this configuration, the wired client would static IP program, instead of the faux-DHCP server emulation (DHCP-to-IPCP gateway) created by the Netgear or Cradlepoint devices.

The economics are also questionable, based the model of Cisco router used.

Today there are alternatives to using a Cat1000 or Cisco 800 ISR with an LTE NIM; there is the new [ Catalyst Cellular Gateway ]:

https://www.cisco.com/c/en/us/products/routers/catalyst-cellular-gateways/index.html

Model CG522-E

 or

CG418-E

Equivalent function, but with 10GB wired ethernet to handle up to 5G  (LTE cat18, etc.) speeds, and POE power source, etc.

[BrianSekleckiGE]

To further clarify: The Netgear and Cradlepoint devices are doing some crazy thing where they convert DHCP client from the wired to issue the IPv4 address obtained from LTE network (via IPCP?).

With a hypothetical working Cisco IRB/CRB config, one would not need DHCP Client on the wired side, just static IP addressing.