Increasing bandwidth to cable router

[ElQueue]

I have a 3750 multi-layer switch connected to an Arris Cable modem from Comcast. The modem has 4 switched ports on the back that I would like to "bundle" together to 4 ports on my switch. Since they are "unmanaged" switch ports on the modem, I can't simply plug them into my switch as they would simply cause a broadcast storm almost instantly, and of course EtherChannel is out of the question. So I thought to myself, "Why don't I just turn 4 ports into routers and then load-balance across them, giving me up to 400mbps of bandwidth out to the Internet?"

I turned ports 2/0/1 - 2/0/4 into "no switchport" ports and gave them DHCP IP bindings to get IP addresses from the modem using "ip dhcp" (since I also have wifi devices connecting to the built-in AP as well, this was necessary). When I plug the ports into the modem, they come up/up, but don't get assigned IP addresses. I enabled DHCP debugging and I see no messages about it even requesting any lease from the DHCP server. I can get devices to get IP addresses if I plug my wireless bridge into any of the 4 ports, so I know the DHCP server is working. And of course I can't even begin to load-balance traffic until the ports have IPs.

What am I missing?

[ElQueue]

I just discovered the "terminal monitor" command and realized that's why the debug info for DHCP wasn't coming to my SSH session. It keeps requesting a lease, filling my screen with more data than I can parse before the next loop goes. The last bits of info given are:
"*Mar 22 00:19:01.705: DHCP: SRequest- Requested IP addr option: 10.0.0.190
*Mar 22 00:19:01.705: DHCP: SRequest placed lease len option: 604800
*Mar 22 00:19:01.705: DHCP: SRequest: 314 bytes
*Mar 22 00:19:01.705: DHCP: SRequest: 314 bytes
*Mar 22 00:19:01.705: B'cast on FastEthernet2/0/2 interface from 0.0.0.0
*Mar 22 00:19:01.705: DHCP: Received a BOOTREP pkt
*Mar 22 00:19:01.705: DHCP: offer received from 10.0.0.1
*Mar 22 00:19:01.705: DHCP: offer received in bad state: Requesting punt
*Mar 22 00:19:01.747: DHCP: Received a BOOTREP pkt
*Mar 22 00:19:01.747: DHCP: rcv ack: Address in use..send DECLINE
*Mar 22 00:19:01.747: DHCP: SDecline attempt # 1 for entry:
*Mar 22 00:19:01.747: DHCP: SDecline placed Server ID option: 10.0.0.1
*Mar 22 00:19:01.747: DHCP: SDecline: 287 bytes
*Mar 22 00:19:01.747: B'cast on FastEthernet2/0/2 interface from 0.0.0.0
*Mar 22 00:19:01.747: DHCP: SDiscover attempt # 1 for entry:
*Mar 22 00:19:01.747: DHCP: SDiscover placed lease len option: 604800
*Mar 22 00:19:01.747: DHCP: SDiscover: sending 302 byte length DHCP packet
*Mar 22 00:19:01.747: DHCP: SDiscover 302 bytes
*Mar 22 00:19:01.747: B'cast on FastEthernet2/0/2 interface from 0.0.0.0
*Mar 22 00:19:01.747: DHCP: Received a BOOTREP pkt
*Mar 22 00:19:01.747: DHCP: rcv ack 10.0.0.1 is not our server 0.0.0.0
*Mar 22 00:19:01.781: DHCP: Received a BOOTREP pkt
*Mar 22 00:19:01.781: DHCP: offer received from 10.0.0.1
*Mar 22 00:19:01.781: DHCP: SRequest attempt # 1 for entry:
*Mar 22 00:19:01.781: DHCP: SRequest- Server ID option: 10.0.0.1
*Mar 22 00:19:01.781: DHCP: SRequest- Requested IP addr option: 10.0.0.191
*Mar 22 00:19:01.781: DHCP: SRequest placed lease len option: 604800
*Mar 22 00:19:01.781: DHCP: SRequest: 314 bytes
*Mar 22 00:19:01.781: DHCP: SRequest: 314 bytes
*Mar 22 00:19:01.781: B'cast on FastEthernet2/0/2 interface from 0.0.0.0
*Mar 22 00:19:01.781: DHCP: Received a BOOTREP pkt
*Mar 22 00:19:01.781: DHCP: offer received from 10.0.0.1
*Mar 22 00:19:01.781: DHCP: offer received in bad state: Requesting punt
*Mar 22 00:19:01.806: DHCP: Received a BOOTREP pkt
*Mar 22 00:19:01.806: DHCP: rcv ack: Address in use..send DECLINE
*Mar 22 00:19:01.814: DHCP: SDecline attempt # 1 for entry:
*Mar 22 00:19:01.814: DHCP: SDecline placed Server ID option: 10.0.0.1
*Mar 22 00:19:01.814: DHCP: SDecline: 287 bytes
*Mar 22 00:19:01.814: B'cast on FastEthernet2/0/2 interface from 0.0.0.0
*Mar 22 00:19:01.814: DHCP: SDiscover attempt # 1 for entry:
*Mar 22 00:19:01.814: DHCP: SDiscover placed lease len option: 604800
*Mar 22 00:19:01.814: DHCP: SDiscover: sending 302 byte length DHCP packet
*Mar 22 00:19:01.814: DHCP: SDiscover 302 bytes
*Mar 22 00:19:01.814: B'cast on FastEthernet2/0/2 interface from 0.0.0.0
*Mar 22 00:19:01.814: DHCP: Received a BOOTREP pkt
*Mar 22 00:19:01.814: DHCP: rcv ack 10.0.0.1 is not our server 0.0.0.0%Unknown DHCP problem.. No allocation possible
*Mar 22 00:19:01.982: DHCP: Waiting for 60 seconds on interface FastEthernet2/0/2
*Mar 22 00:19:01.999: DHCP: Received a BOOTREP pkt
*Mar 22 00:19:01.999: DHCP: offer received from 10.0.0.1
*Mar 22 00:19:01.999: DHCP: offer received in bad state: Purging punt
*Mar 22 00:19:01.999: DHCP: Received a BOOTREP pkt
*Mar 22 00:19:01.999: DHCP: offer received from 10.0.0.1
*Mar 22 00:19:01.999: DHCP: offer received in bad state: Purging punt"
When I use debug dhcp detail, it shows that it's sending me IP addresses that are in use, declining others, etc.

[Joseph W. Doherty]

Your 4 routed ports, on your 3750, need to be in different networks. Your Arris might not support that. If it does, you should be able to "load balance" across then. Which may allow you to accept ingress of over 100 Mbps. Unfortunately, you won't be able to effectively shape your egress to the Internet, where generally Comcast cable modems offer only 5 to 20 Mbps.

A "better" approach might be to . . .

If your Arris cable modem only provides FE ports, upgrade it to a cable modem that provide gig.

If your 3750 doesn't support gig, either consider replacing it with a model that does, or consider placing a small gig L2 switch between the (gig) cable modem and the 3750, and run Etherchannel between the two switches.

[ElQueue]

My Arris modem has the 4 GB ports, but my 3750 only has FE ports. It has 2 modular ports for gigabit, but I'd have to buy them (Not too crazy, but since I'm training for my CCNA I thought I'd give a shot at this arrangement). My allotted bandwidth is 150mbps, so even if I only got 2 working I could load balance across the 2 ports and get close to no congestion internally at peak.

As for the different networks thing, I thought that as long as I had 2 routes with the same cost I could load balance across them regardless of the network they were on. So if I had 2 ports on the 10.0.0.0 network getting IPs from the modem, I thought the switch (with L3 routing enabled) would send data out both those ports either based on source MAC/IP, destination MAC/IP, IP port, etc.

Either way, until I can get the DHCP thing figured out, this is going nowhere.

Something that just came to me is this: Is DHCP having an issue because the ports have the same MAC address even though they're different ports? If so, would I be able to use 2 3750s Etherchanneled together to perform this (yes, I have 2)?

[Joseph W. Doherty]

"Something that just came to me is this: Is DHCP having an issue because the ports have the same MAC address even though they're different ports? "

Each routed port, I believe, would have its own unique MAC. Again, though, you cannot have multiple interfaces in the same network.