Design question

Unanswered Question

Hello everyone -


I have a design question that involves a Cisco ASA firewalls (2 actually, one of them is for failover), a stack of 3750 switches and a Cisco 3845 router. I am a little confused about how the equipment should be connected for optimal routing and switching at our data center.


Here's the scenario. We will have 3 VLAN's hosting different kinds of servers. These servers need to be accessed by all sites that are connected to our MPLS cloud. The 3845 router too will be connected to the MPLS cloud from our data center. The ASA's (also at the DC) will be connected to an Internet router for Internet connectivity.


So here are my questions:


1. how should the 3845 router be configured so that it routes traffic to different sites, but also provides access to the internet from servers in all different vlan's?

2. would i need to create a trunk port on each switch in the stack or just 1 trunk port for the stack should be enough?

3. would I need a router interface and an ASA interface on each vlan?


I am a little confused about this thing...So any help would be greatly appreciated!!

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Jon Marshall Fri, 03/21/2008 - 02:52
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Hi


1) Yes the 3845 should be responsible for routing traffic between your MPLS sites.

No it should not provide access to the Internet for your servers. All your internal devices should go through the ASA to access the Internet.


2) Not sure i follow. Most of the ports on your 3750's will be access ports for your servers.


3) No you don't. What i would suggest is that you make the 3750 responsible for routing between the vlans in our DC.


Next you can create a L3 point to point link from your 3750 to the 3845 router.


Finally you create a dedicated vlan for connecting your 2 ASA firewalls to the 3750's and add a default-route on the 3750's pointing to the inside interface of the ASA.


HTH


Jon

Ok, to make things simpler, lets assume I have a single 3750 switch which needs 2 VLAN's on it. The respective VLAN IP addresses on the 3750 will be the default gateway for the servers in those two respective vlan's. The 3750 switch will need to be connected to a 3845 router (which is connected to the MPLS cloud). OSPF will be configured for dynamic routing between the 3845 router and the 3750 switch.


My question now is:


1.) Can I use the native VLAN on the 3750 switch to connect to the 3845 router? Or should I create another VLAN on the 3750 for communication with the router?

2.) If the 3750 switch needs to connect to an ASA 5510 for the Internet, should that connection be on the native VLAN or a separate VLAN as well?

3.) If I need 2 DMZ's on the ASA, can I create additional VLAN's on the 3750 for the 2 DMZ equipment? If yes, then would the equipment in the DMZ's use the vlan interface as the default gateway or the will they use the ip address of the dmz interface as their default gateway?


Thanks again!

Jon Marshall Fri, 03/21/2008 - 14:09
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1) I would make the connection between the 3750 and the 3845 a routed link rather than using a layer 2 link ie. on the port that the router connects to


int fa0/1

no switchport

ip address 192.168.5.1 255.255.255.252


on the router


int fa0/1

ip address 192.168.5.2 255.255.255.252


2) Make this a separate vlan dedicated for the 3750 and the ASA ie. not other devices should be on this vlan.


3) If you use the 3750 for your DMZ's then machines on the DMZ have to use the ip address assigned to the interface on the ASA, otherwise they could route around the ASA.


HTH


Jon

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