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Multiple internet connections on one network

Good evening:

I apologize in advance for the word vague here.   Have a client with a rather elaborate network consisting of a T1 connection on a Cisco Router (that we are not allowed to touch) This has a gateway address on the unnumbered ethernet.  

This plugs into what they call a "core" router a Cisco 3560G on a Vlan 78.  They have all of their workstations on this vlan 78; which is a network (mask /24).  There are 18 other vlans based upon the 10. (so it's a A vari-netted.)  

The "core" also utilizes a default gateway of ..

The idea was to install a 35/5MB link from time warner cable. This has a static IP and a subnet of .252  

Tried creating a port on the Cisco 3560G, called it vlan 802; set it as a trunking port; with access to all the vlans including vlan 78 (where the workstations site.)

Changed the default route on the switch to (time warner connection.)

I can ping the gateway; and interface address from a serial connection into the 3560G. I can ping the vlan address from vlan 78 workstations. However, anytime I originate traffic; it keeps coming back as  

The question being: the switch is IP routing enabled; is it that the time warner device (a motorola bit surfer pro) is too dumb...  why does traffic continue to point back the way it does (the VLAN 78 default gw is .. btw.

Sorry for the lack of information; it's been a long 2 days without sleep ... any help is voluminiously appriciated.
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Have you setup 802.1q (vlan tagging)?
If you are using IP unnumbered the IP address of the Ethernet Interface is used, which is why you are seeing that IP address reported.
You need to configure a static TimeWarner IP address on the interface connected to TimeWarner.  Then the IP that will be reported will be the TimeWarner IP address vs. the internal Ethernet IP address.  

I wouldn't recommend having their internal network connected directly to the internet router.  They need a firewall between the router and their internal network for protection.
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Gsmartin -

I have the time warner IP assigned to the router via vlan configuration. (interface vlan 802 - Ip address timewarner .) switchport access vlan 802.

I can ping time warner from that router;

the issue here is when the other vlan 78 has a workstation on it as a for example) default gateway (which is the ip of the 10.x network on the switch vlan)

Can't go from that vlan to the 802 vlan and get traffic; it wasnts to traceroute back to (which is a router I don't have control over) (t1 connection) that previously provided. Even though; the switch gateway of last resort was changed to the TW connection.

The IOS is 12.2.35(se5) which should route vlans ... even so I can ping from a serial connection to google for example. If i take my laptop (on that same switch though) put it in vlan 78 ... no good.   Perhaps, tagging is the issue   I did setup the time warner connection as a trunk ... dot1q; and did switchport access vlan 78 on the port i have the workstation connected too.  

I'll try it again and let you know. again, thank you for the input; it is valueable to me.  

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