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2 Messages

Thursday, September 28th, 2023 9:52 PM

BGW320 Assign Multiple Public Static IPs to Devices

We have a /29 static IP block from AT&T and would like to assign a public IP from our allotted subnet to 2 separate devices within our local network. 

Both devices are connected via ethernet to the Ethernet/5G Ethernet ports on the router

Followed the guide described here for allocating a public address to each device: https://forums.att.com/conversations/att-internet-features/how-do-i-setup-an-att-internet-static-ip/5defee02bad5f2f606ea4054

Aattempted a few different configurations to get this to work to no avail.

We're able to assign public static IPs to both devices, but:

- unable to access anything outside of the local network

- unable to receive requests from the public network

Neither device can be pinged or tracerouted from the public network. 

Traceroute attempts to either of the public static addresses stop at the address identified as the "Broadband IPv4 Address" on the router: 75.7.XX.X7 

BGW320 - Primary Broadband Status

Broadband Network Type iPAG
Broadband IPv4 Address 75.X.3X.X7
Gateway IPv4 Address 75.X.3X.1

BGW320 - Home Network Status

Device IPv4 Address 192.168.1.254
DHCPv4 Netmask 255.255.255.0
DHCP Server On
DHCPv4 Start Address 192.168.1.64
DHCPv4 End Address 192.168.1.253
DHCP Primary Pool Private
Secondary Subnet Enabled
Public Subnet 76.2XX.XXX.214/255.255.255.248
Cascaded Router Status Disabled
IP Passthrough Status Off (private IP address)

BGW320 - Subnets & DHCP

Private LAN Subnet

Device IPv4 Address 192.168.1.254
Subnet Mask 255.255.255.0

DHCP Server

DHCP Server Enable On
DHCPv4 Start 192.168.1.64
DHCPv4 End 192.168.1.253

Public Subnet

Public Subnet Mode On
Allow Inbound Traffic On
Public Gateway Address 76.2XX.XXX.214
Public Subnet Mask 255.255.255.248
DHCPv4 Start 76.2XX.XXX.209
DHCPv4 End 76.2XX.XXX.213
Primary DHCP Pool Private

- The 2 devices that were allocated public static IPs are using addresses within the public block above (i.e.76.2XX.XXX.211 and 76.2XX.XXX.212).
- These IPs are specified with the expected mac address within the IP Allocation tab on the router.

- All firewall options are turned off/set to No. 



I noticed that the public IP of the router isn't in the same subnet as the public subnet we were assigned. Is that normal/expected?
For example:

- router broadband gateway IP: 75.X.3X.1 
- public subnet gateway IP: 76.2XX.XXX.214
75. vs 76.

Given where the traceroutes stop, it seems like the router doesn't know how to route properly between the router and the public subnet.

ACE - Expert

 • 

34.4K Messages

5 months ago

I noticed that the public IP of the router isn't in the same subnet as the public subnet we were assigned. Is that normal/expected?

Yes, this is expected.  I don't see anything that jumps out at me as clearly wrong. 

How exactly are your two devices configured?  Are they statically configured with 76.2XX.XXX.211 and 76.2XX.XXX.212 respectively?

Is their netmask set up for 255.255.255.248

Is their Default Gateway setting for each 76.2XX.XXX.214?

What happens when you ping 76.2XX.XXX.214 from the two nodes?

What happens when you ping the two nodes from the Gateway?

What happens when you traceroute 8.8.8.8 from the two nodes?

Where does a traceroute from "elsewhere on the Internet" lose its way when aiming for 76.2XX.XXX.211?

(edited)

2 Messages

5 months ago

@JefferMC 

How exactly are your two devices configured?  Are they statically configured with 76.2XX.XXX.211 and 76.2XX.XXX.212 respectively?

Is their netmask set up for 255.255.255.248

Is their Default Gateway setting for each 76.2XX.XXX.214?

    • Both devices are configured via DHCP, but statically assigned public IPs from within the router IP allocation menu.
    • Netmask and default gateway are configured correctly as you stated.

What happens when you ping 76.2XX.XXX.214 from the two nodes?

    • They ping successfully to the 214 address.

What happens when you ping the two nodes from the Gateway?

    • If by gateway, you mean the ATT router, then using the diagnostic tool, pinging the two nodes is successful.

What happens when you traceroute 8.8.8.8 from the two nodes?

    • This succeeds from both nodes.

Where does a traceroute from "elsewhere on the Internet" lose its way when aiming for 76.2XX.XXX.211

    • Traceroutes from outside the network consistently stop at the "Broadband address" for the ATT router: 75.X.3X.X7
    • However, traceroutes from outside the network to the subnet gateway 76.2XX.XXX.214 succeed. Although, it does not traverse the broadband address where the traceroute above stops. 

ACE - Expert

 • 

34.4K Messages

5 months ago

Are your two nodes configured to respond to ICMP?

Do they have software firewalls?  Are their software firewalls configured to pass ICMP?  Can you see if the ICMP packet from traceroute is getting dropped?

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