Can someone help me with Time Warner Cable subnet and 2621?

[commandlinekid]

Can someone help me?

I have a 2621 (with Cisco VLAN switch behind it but not relevant to conversation) into which I plugged a Time Warner Business Class cable connection.

It goes through a bridged (I set the modem to bridged myself) Arris dg1670.

My WAN IP on the 2621 is set to dhcp on FastEthernet 0/0. And it IS pulling from Time Warner. I can also ping from the 2621 the IP 8.8.8.8.

The LAN IP is set to my subnet (and I put it on FastEthernet 0/1.4 exactly the setup my DSL used to use except using a different subnet)assigned by Time Warner of (fake) 111.111.111.41 255.255.255.240 (so I have a /28). This is the first address in the subnet.

I set my default route on the 2621 to:

ip route 0.0.0.0 0.0.0.0 fastethernet 0/0 dhcp

And I took off any access-lists from the interfaces.

PROBLEM: The 2621 is not routing the subnet assigned to FE 0/1.4. My test for this was to ping From the 2621 out to 8.8.8.8 using the advanced ping out of the interface FE 0/1.4....and it's just not going.

Can anyone help me here? Thank you very much.

-Joe

[Jon Marshall]

When you use DHCP on the outside interface is the IP it gets assigned from your /28 subnet or from a different range ?

Jon

[commandlinekid]

Different range. Completely different Class A alltogether. And yes, from that WAN port I can then ping 8.8.8.8

Also, I added no ip proxy-arp but no change.

Is it a "non starter" if when I run ip debug packet I get Nothing? Especially when I say...try to ping the first address (assigned to FE 0/1.4) from the public internet and get nothing? Shouldn't they at least be "trying" to hit my router if they had a proper route in on the TW side?

[Aaron O'Hare]

They should be and this sounds like an issue on the TWC side but since they've been so unhelpful looking for alternative possibilities.

[Jon Marshall]

They should but it all depends how they set it up.

That modem is going to need a route to that subnet pointing to the outside interface IP of your router.

You may be able to add one assuming they are routing the subnet to you.

If you can't add a route then the alternative is usually to NAT all your server IPs to the outside interface of you router but that is for private IPs and you are using public ones so it defeats the purpose.

But you did mention if you used that /28 beween your router and the modem it worked (or I may have misundertstood that part).

If it did then you could use the /28 to connect your router to their modem and then you address your servers using private IPs.

The spare IPs in that subnet can then be used to do NAT for the servers and those IPs do not need to be assigned to any interfaces on your router.

You would need to reenable proxy arp for this to work.

Jon

[commandlinekid]

Thank you for helping me with a creative answer but I'm not using private IP's on the server side...there are providers I could switch to who take routing seriously. 

I have another trick I want to try with them. I'm going to tell them to setup the modem as a router, not A bridge. Right now it's a bridge but, although I can pull a WAN IP, it appears to Not be routing me my /28 right?

IF I told them to setup the router as an actual router so they are assigning me the first address in the subnet as the LAN IP on their acutal modem (ie....them expecting me to use them as the router), I could possibly get in there and reassign that LAN IP to a fake subnet and try to route the traffic to another fake IP I setup as the WAN IP on my router.

That way....since we know the new /28 actually "gets to my lan" with their routing setup, Whatever ROUTE they are setting to do that via a script or whatever....will still be set. 

Who knows, I'll try it. Thank you for all your help.

[Jon Marshall]

No problem, I understand why you wouldn't want to use private IPs.

It may be that they are using secondary IPs on their router ie. they have an IP from your /28 range on the same interface and so instead of routing to your subnet they simply send an arp for it which assumes you are using that IP subnet between your router and them.

I have seen this setup before

It obviously won't work if you have that IP subnet on a different interface.

Basically you are right when you say they appear not to be routing to your subnet.

Usually for your setup to work the ISP will assign you a separate subnet for your connection to them and then route the other range to your router.

The fact they are using DHCP suggests this won't work.

If you can get them to setup the modem as a router and you can add routes to it then yes you should be able to get it to work.

After all if they are assigning you a range then they should be able to route it to you.

Jon