No route between two public IP addresses obtained from one modem.

[johnqhu]

Hi guys,

I managed to get two public IP addresses from my modem in bridge mode. I attached one unmanaged switch to the modem first and then connected my two own routers to the switch. Thus I got two IPs. And I tried to get more and found out only two available.

Each of them works fine, both could be used to setup private networks. But I found a problem, there is no direct route path between the two IPs. Let's name the two IPs(or subnets) as A and B. That is, if I setup a server in B (port forwarding to open port to internet), I cannot access it from A directly. Vice versa. However, if I use NordVpn or Cloudflare Warp client in A, I can access B from A. And there is no problem to access the server in B from other people's home or use cell phone data.

I tried traceroute (from A to B), the result is:

C:\> tracert (IP of B)

Tracing route to pool-xxx-xxx-xx-xxx.cpe.net.cable.rogers.com [IP of A]
over a maximum of 30 hops:

1 <1 ms <1 ms <1 ms 192.168.1.1
2 13 ms 14 ms 11 ms pool-xxx-xxx-xxx-xxx.cpe.net.cable.rogers.com [gateway of A]
3 * * * Request timed out.
4 * * * Request timed out.

.........
30* * * Request timed out.

It seems there is no route after the gateway.

I contacted the tech support of Rogers, they just refuse to solve the problem. Always insist:

"out of support scope"

Anyone have the same problem?

***Edited Labels***

[-G- · Accepted solution]

@johnqhu Which modem/gateway are you using?  If you are an Ignite Internet customer (with an XB6, XB7 or XB8 gateway) you can only have ONE external router attached or else the configuration will be very unstable.

See the following recent discussion about this: https://communityforums.rogers.com/t5/Internet/Getting-only-one-IPv6-address/m-p/530288

[Datalink]

@johnqhu the issue where there's no route between the addresses most likely isn't a problem, unless of course that is exactly what you're attempting to do.  Rogers modems have in the past provided two IP addresses from the modem when its operating in Bridge mode, taking note of @-G-'s comments regarding the Comcast XBx modems.  I don't use Ignite TV, so, I've been able to run two separate IP addresses without issue from the modem, however, those are IPv4 addresses only.  I didn't check for two independent IPv6 addresses, so, I'll have to put that on my list of things to do.  

For your complaint regarding lack of access between the two addresses, Rogers modems have always operated in that way, treating the two addresses and networks as completely independent networks.  The previous Hitron modems operated in that manner.  That goes back as far as 2013/2014, and the previous Cisco modem before that probably operated in the very same manor.  Very very few customers have ever indicated that they want two IP addresses while at the same time indicating that they wanted complete access back and forth between the two networks.  

[johnqhu]

Read that post. For me, I didn't use IPv6. I made two pure IPv4 networks. The two work both no problem solely. And only issue is to access each other.

[johnqhu]

Currently, I don't need IPv6. So it's not a problem for me now. I got two IPv4 and they work fine just as what you described. Now I know the two addresses can never be accessed from each other. Thanks for the information. Just wondering why Rogers did that way? It should be easy to solve. Just need to modify the route rules. 

[-G-]

Let me put it a different way.:

With the old Hitron CODA gateways, when you enable Bridge Mode, it shuts off all the internal services and (for the most part) reduces it to a simple cable modem.  Rogers lets you obtain public IP addresses for 2 devices and both are available for external routers.

With the Ignite gateways, "Bridge Mode" bridges the LAN and WAN interfaces so that an attached external router can obtain public IPv4 and IPv6 addresses.  However, it still has internal services running.  The Ignite Gateway takes one of the IP address allocations that you are allowed, and that leaves you with only one that can be used by an external device.  If you connect two external routers, you will end up with three devices (the two routers and the Gateway) competing with each other for the two addresses that are allowed.

[johnqhu]

I understand what you mean. But it seems it never happened to me. The two networks of mine never have problem when work separately. Maybe it's because I only have IPv4 network. No IPv6.

[-G-]

Well, there is definitely something weird going on from a routing perspective.  I tried a slightly different test where I pinged the WAN IP address of an Ignite gateway that was connected to the same CMTS, and I got the following results:

% ping [IP address redacted]

PING [IP address redacted]: 56 data bytes

ping: sendto: No route to host

ping: sendto: No route to host

Request timeout for icmp_seq 0

ping: sendto: No route to host

Request timeout for icmp_seq 1

ping: sendto: No route to host

Request timeout for icmp_seq 2

ping: sendto: No route to host

Request timeout for icmp_seq 3

ping: sendto: No route to host

Request timeout for icmp_seq 4

ping: sendto: No route to host

Request timeout for icmp_seq 5

ping: sendto: No route to host

And on the next ping test to the same IP address, a few seconds later, I saw this:

% ping [IP address redacted]

PING [IP address redacted]: 56 data bytes

Request timeout for icmp_seq 0

Request timeout for icmp_seq 1

Request timeout for icmp_seq 2

Request timeout for icmp_seq 3

Request timeout for icmp_seq 4

Request timeout for icmp_seq 5

I don't know whether this is due to a quirk in Casa's implementation or deliberate configuration on Rogers' part.

@johnqhu Unless Rogers has loosened some restrictions, I still maintain that having two routers connected to an Ignite Gateway (that is in Bridge Mode) will result in an unstable configuration.

That said, I can still replicate the connectivity issues that you described in your initial post, and this was done between two homes that are in a 100% Rogers-supported configuration.

[-G-]

Just a followup.  Did some more testing and I'm not seeing any routing weirdness at the moment.

I should have made it clear in my last post that it's normal for my pings (ICMP Echo Requests) to be ignored.  I can do some proper connection tests when time permits.  However, at least I am not getting any unexpected ICMP responses with the limited testing that I can do at this time and the Rogers network seems to be functioning normally.