Equipment (Modems,Gateways)
Back to Top

Netgear CG3000DCR and Static Routes

Guitardood
Visitor

Netgear CG3000DCR and Static Routes

Have been using Comcast's SMC for a long time with no issues. Recently upgraded speed to 150 and was told the SMC wouldn't support it so they brought out a Cisco.  The Cisco's Static Routing did not work and had extremely high latencies just pinging from my main intranet router to the local Cisco's local interface.  Ping times as high as 25ms where it typically should be between 0 and 1.

 

So I had them come out and replace the Cisco with a Netgear CG3000DCR.  Ping times now back to what is normally expected, however, this modem's static routes do not behave properly either.  I have the Comcast/Netgear's local pointing interface set at 172.31.3.1/30 with my router's internet facing interface at 172.31.3.2/30.  Netgear's DHCP is disabled.  I've added the static routes in the Netgear pointing the entire class A subnet 10.0.0.0/8 to 172.31.3.2.  The 10.x.x.x subnets are to be handled on my side of the equation.  However, it seems that the Netgear is completely ignoring these static routing table entries and any communications (ping from 10.x.x.x equipment to 172.31.3.1, ping from Netgear's diagnostic screen ping utility to one of my local machines) fails.  The comcast seems to only respond to our true static IP or the 172.31.3.2.

 

I spoke with a tier 2 technician who is telling me that Comcast doesn't support the static routing, despite it being a configuration screen in the modem and a required part of normal network connectivity.  This is also exactly how everything was configured with the previous SMC modem and was functioning perfectly.

 

Can somebody please respond regarding this supposed policy change at Comcast, regarding their disabling and/or not supporting a standard networking protocol like static routing?  Also, how you reconcile this lack of support with Title II.

 

Regards,

guitardood

curtisv
New Contributor

Re: Netgear CG3000DCR and Static Routes

Guitardood,

 

Please read RFC 1918 "Address Allocation for Private Internets".  Nets 10/8, 172.16/12, and 192.168/16 cannot be routed by Comcast (or any provider).  You have to have a NAT (network address translator) to connect to the rest of the Internet.  See RFC 1631 "The IP Network Address Translator (NAT)".

 

You should be setting up a NAT on your cable modem, not static routes.  Your cable modem is correctly ignoring static routes to addresses that have no significance in the global routing space.  The NAT will take requests to the outside world and translates the 10/8 address and port to the NAT's public side address and a randomly selected port and saves that mapping so it can do the reverse mapping.  The other side (a web server or whatever) responds to your NAT's address and port and the NAT translates back to the 10/8 address and port and send packets back to the device with the 10/8 address.

 

Curtis

 

Guitardood
Visitor

Re: Netgear CG3000DCR and Static Routes

Thanks for the response.

 

Actually, I have my own router on my side of the Comcast which handles all of my networks static ip assignments, routing and/or NAT'ing.  I don't want the Comcast to do anything except look at my single solitary router as the boss of my network.  I see all kinds of traffic coming in from Comcast on 10.x.x.x addresses and if I ping any of my 10.x.x.x addresses from the modem's utility page, they cannot be reached.

 

Best,

guitardood

Labels
Discussion stats
  • 2 replies
  • 612 views
  • 0 kudos
  • 2 in conversation