Network Configuration Oddities

[claytoncarney]

I have the following network setup:

* Actiontec M1000 DSL Modem/Router - configured as the network gateway:
- ISP Protocol: PPPoE
- Modem IP Address: 192.168.0.1
- Subnet Mask: 255.255.255.0
- DHCP Server: On
- DHCP Start: 192.168.0.3
- DHCP End: 192.168.0.254
- DHCP Subnet Mask: 255.255.255.0
- Dynamic DNS: On
- NAT: On

* Linksys WRT54G2 Wireless Router - configured as an access point:
- Internet Connection Type: Automatic Configuration - DHCP
- Local IP Address: 192.168.0.2
- Local Subnet Mask: 255.255.255.0
- DHCP Server: Off
- Operating Mode: Router (not Gateway)
- RIP: Disabled

The M1000 is connected to the WRT54G2 via CAT5 cable between the Ethernet ports on each device (not the WRT54G2 WAN port). The NIC on my Windows 7 PC is connected to the WRT54G2 via CAT5 cable between the Ethernet ports on each device.

This setup works (connects to internet, connects to wireless devices, etc.) but there are some oddities that I do not understand:

1. The Network Map (Control Panel -> Network and Sharing Center -> See Full Map) shows a device chain of PC -> WRT54G2 -> Gateway -> Internet (which is correct). However, when I right-click on the Gateway, it shows two devices: Actiontec M1000 and Actiontec TR64 M1000. This makes absolutely no sense to me.

2. The MAC Addresses reported by the Network Map for the WRT54G2 and the Gateway are off by one from the values reported by the device Management URL (e.g. WRT54G2 - Network Map says 00:23:69:7e:ac:4b; Management URL says 00:23:69:7e:ac:4c). Weird.

3. Running 'ipconfig /all' reports the primary DNS Server is 192.168.0.1 (the gateway) and the secondary DNS Server as one of the ISP's DNS servers. When I run an 'nslookup' on a domain name, I always get two 'DNS request timed out' errors (presumably from the gateway) before it returns the addresses (presumably from the ISP's DNS server). I don't understand why the gateway is being set as a DNS server rather than the ISP's DNS servers which are normally set via DHCP.

Does anyone have a clue what would cause these oddities?

Thanks

 

[Johnathan Lyman]

1. The Network Map (Control Panel -> Network and Sharing Center -> See Full Map) shows a device chain of PC -> WRT54G2 -> Gateway -> Internet (which is correct). However, when I right-click on the Gateway, it shows two devices: Actiontec M1000 and Actiontec TR64 M1000. This makes absolutely no sense to me.

Windows may be trying to understand your Actiontec the only way it can and given it's a modem AND a router (and can be one but not the other, as well) It may have two technical names?

2. The MAC Addresses reported by the Network Map for the WRT54G2 and the Gateway are off by one from the values reported by the device Management URL (e.g. WRT54G2 - Network Map says 00:23:69:7e:ac:4b; Management URL says 00:23:69:7e:ac:4c). Weird.

See answer #1. 4b may be router, 4c may be modem?

3. Running 'ipconfig /all' reports the primary DNS Server is 192.168.0.1 (the gateway) and the secondary DNS Server as one of the ISP's DNS servers. When I run an 'nslookup' on a domain name, I always get two 'DNS request timed out' errors (presumably from the gateway) before it returns the addresses (presumably from the ISP's DNS server). I don't understand why the gateway is being set as a DNS server rather than the ISP's DNS servers which are normally set via DHCP.

Does anyone have a clue what would cause these oddities?

Thanks

Not really a big deal. If you have manual IP settings, I'd suggest using different DNS servers altogether. I like google's: 8.8.8.8 and 8.8.4.4.

I agree with you, all odd stuff.

 

[claytoncarney]

Thanks Johnathan!

Was not aware of Google DNS.

Interesting discovery. Changed the modem DHCP Server DNS setting from Dynamic to Static and entered the Google IPs. After DHCP renew, found primary DNS was still the Gateway and secondary DNS was the primary Google DNS.

Appears the answer to Oddity #3 is that the M1000's DHCP Server is simply returning the wrong values for DNS. Probably the firmware stores Gateway, Primary DNS, and Secondary DNS sequentially in memory and the DHCP Server is using the wrong memory offset to return the DNS values. Have the latest firmware available, so the only fix is setting static DNS in the Windows TCP/IPv4 stack.

 

[chev65]

Thanks Johnathan!

Was not aware of Google DNS.

Interesting discovery. Changed the modem DHCP Server DNS setting from Dynamic to Static and entered the Google IPs. After DHCP renew, found primary DNS was still the Gateway and secondary DNS was the primary Google DNS.

Appears the answer to Oddity #3 is that the M1000's DHCP Server is simply returning the wrong values for DNS. Probably the firmware stores Gateway, Primary DNS, and Secondary DNS sequentially in memory and the DHCP Server is using the wrong memory offset to return the DNS values. Have the latest firmware available, so the only fix is setting static DNS in the Windows TCP/IPv4 stack.

If you don't like the oddities you could simply upgrade your modem to a modem only not a combo modem-router then get a wireless N router that can handle both wired and wireless connections.

 

[joeldbenson]

The real answer to Oddity #3 is that the M1000 acts as a caching DNS server (as most DSL modems do) and its DHCP Server configures your network devices to use it rather than going out to an internet DNS server because it is faster.
So setting static DNS in the Windows TCP/IPv4 stack will only slow down your internet accesses.