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TOPIC: Routing Design

Routing Design 10 years 4 months ago #15658

  • jwj
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So I have a friend who called me recently asking for some help. He rushed into a project without planning, and frankly I'm having troubles coming up with a good solution for him.

Scenario: company connects to 2 different ISP's using static routes. Each ISP has assigned a few Class C networks to them. Currently, in order for ISP A address space to communicate with ISP B address space, it is routed completely out to the internet and back.

They have recently purchased a small Dell layer 3 switch, to have these subnets route to each other without going out the internet and back. They also want ISP A's outbound to go out to ISP A only and ISP B's to go out ISP B only. This part has me stuck. I'm not sure there's a way for a default route to do this from the Dell switch. Any suggestions?
-Jeremy-
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Re: Routing Design 10 years 4 months ago #15663

  • jwj
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I was thinking today that an access list on the egress interfaces for the Dell would do the trick. Anyone else with a better suggestion please post. Thanks.
-Jeremy-
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Re: Routing Design 10 years 4 months ago #15812

  • Brandonh
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Are you saying that you have two neworks with their own internet connection in the same building and you want them to use their own internet but yet beable to send packets between both networks without going out of the internet ? So you basically want theese two networks on the same LAN but remaining different subnets?
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Re: Routing Design 10 years 4 months ago #15829

  • TheBishop
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Can you use the default gateway entries on each side? If the default gateway points to the appropriate ISP then the traffic will go there unless some other route applies. Then if you add static routes for the other subnet pointing to the Dell switch you will get connectivity between the two subnets. However since it's a specific route it will only aplly to inter-subnet traffic and not to traffic destined for the internet.
Or have I misunderstood it completely?
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Re: Routing Design 10 years 4 months ago #15834

  • eylli
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I think you should do something like Bishop said. So on the ege router of each other isp add an eth interface, add static routes

create vlans on the switch and route them on the dell switch.

Regards

Ps. If I also have understood well.
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Re: Routing Design 10 years 4 months ago #15843

  • jwj
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I've got the LAN side worked out with inter-VLAN routing for the networks. That wasn't the problem. I was just looking, for example, at getting just VLAN 1-5 to go out to ISP A for the internet and VLAN 6-10 to go out to ISP B.

Here's a quick layout.

Dell -> 2 Cisco 2600's -> ISP A & B
-Jeremy-
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