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SH 2 in Modem Mode: Unable to ping 3rd party Mail Server

Set up:

SH 2 in Modem Mode

Ubiquity UDM Router

Pi Hole for DNS (OpenDNS)

I have a VPS that runs as a personal mail server.   I have just recent upgraded the VPS and its IP address has changed.  The new IP attached to the FQDN has propagated around to all the major DNS providers.   With the above setup I can no longer ping the IP address or FQDN of the VPS returns the standard "Request Timed Out".   I have gone through 2 VPN services I own and it all works fine.  Other family member on other networks have no issues getting to the server.

Through a process of elimination I have now gotten to the SH 2 being the issue. The SH 2 has been in Modem Modem since the day it was installed well over 5 + years now.  I put the SH 2 into its standard router mode and I can ping my server and access webmail through its FQDN.  This is not my preferred configuration. 

I am a cyber security professional with a good understanding of networks.  Can someone please explain why this work in one configuration but not another. I have checked to see if my Modem Mode IP was blacklisted for some reason but that's fine.  Its plain that the problem lies with the SH 2.

With all of the above, I would be grateful if the Mods could raise a ticket please to have my SH 2 replaced as it appears to be faulty.  More than happy and competent to do self install. Please DM/PM me for account details.

Many thanks 

Thyper

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Re: SH 2 in Modem Mode: Unable to ping 3rd party Mail Server

Hello

If the ping / webmail works in router mode I very much doubt that the issue is with the hub in modem mode as all traffic is passed to your your router.

If you ping from the pi Hole what happens ?

I don't know the Ubiquity UDM Router but is there any way you can ping from that device ?

When did the  IP address change on the VPS ?

Regards Mike

 

 

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Re: SH 2 in Modem Mode: Unable to ping 3rd party Mail Server

Hi Mike

Thanks for the quick response.

If you ping from the pi Hole what happens ? - In Modem Mode "Request Timed Out", In Router Mode pings fine.

I don't know the Ubiquity UDM Router but is there any way you can ping from that device ? again In Modem Mode "Request Timed Out", In Router Mode pings fine.

When did the  IP address change on the VPS ?  72 hour ago.  Used many of the DNS checker sites to monitor propagation which took about 48 hours to complete. Also raised a ticket with the VPS provider (UK Based) to check their DNS records and also to see if my original modem mode IP was being blocked.  They have confirmed all DNS records are correct and are NOT blocking traffic.

Also ran ping, pathping and a tracert against the new IP with DNS configured to each of the major DNS providers one at time in Modem Mode, again either request timed out or trace did not complete.  In Router Mode it pings and resolves.

Hence my conclusion it being an issue the SH 2.  In modem Mode it just passes traffic to the next hop ie acts as dumb switch/hub. That's what is baffling me and calling out the SH 2 as faulty.

Regards

Thyper.

 

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Re: SH 2 in Modem Mode: Unable to ping 3rd party Mail Server

Hello

The only other thing to check is the firewall logs on your router as something is blocking the IP when in modem only mode, this wouldn't be the hub it gotta be something on your network or at the host. Getting a replacement hub will not resolve that as you will have the same problem.

Regards Mike

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Re: SH 2 in Modem Mode: Unable to ping 3rd party Mail Server

Your SH2 is not faulty the IP you get when in modem mode is blocked connect a PC to modem mode to get a new WAN IP and try that if it works copy its MAC to the UDM Router.

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Re: SH 2 in Modem Mode: Unable to ping 3rd party Mail Server

OK I look at the firewall logs again. I do that as a day job!

Many thanks for your help.

Regards
Thyper
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Re: SH 2 in Modem Mode: Unable to ping 3rd party Mail Server

Legacy1

Thanks for the tip i'll give it a go.

Akin to old school MAC address security!

Regards
Thyper

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Re: SH 2 in Modem Mode: Unable to ping 3rd party Mail Server

Legacy1

Just tried, the Ubiquity UDM router does not allow MAC address cloning of a new address to it.

Do you know how long it takes for the DHCP lease to expire when in Modem Mode or am I stuck with a infinite DHCP lease to the original Modem Mode IP?

Regards

Thyper

 

 

 

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Re: SH 2 in Modem Mode: Unable to ping 3rd party Mail Server

Hello

Even once the Lease expires then due to the way that the Dynamic leases are handed out, you will most likely get the same IP address, the only way to renew a lease is too leave the router off for an indeterminate length of time, as the IP address will only change if a new device is add to your part of the VM network, or the network is re-segmented. Leases are issued based on the physical hardware address of the device attached to the hub when in modem only mode.

My lease has expire a number of times since install but I always have the same IP address.

Regards Mike

 

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Re: SH 2 in Modem Mode: Unable to ping 3rd party Mail Server


@Thyper wrote:

Do you know how long it takes for the DHCP lease to expire when in Modem Mode or am I stuck with a infinite DHCP lease to the original Modem Mode IP?

 


When you change the MAC all you have to do is power off the hub for 2mins and on with the new MAC and that will get you a new IP.

 

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