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Network design questions - Layer 3 switches w/ ASAs

Posted on 2010-11-17
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Last Modified: 2012-05-10
Hi,

I am preparing an upgrade to our network, we have 2 x ASA 5510 Sec Plus devices, and 2 x Cisco 3560 L3 switches.

I am planning on doing Active/Passive with the ASAs at the edge, however, I'm worried about interVLAN routing on the layer 3 switches as far as ACL management. I want to use the 3560s as the default gateway (HSRP) for all the equipment behind in order to use wire speed transfers between VLANs. ACL management on the ASA is infinitely easier to manage than on the L3 switches. I'll need 2 sets of ACLs (which will be mostly the same since it is multi-tenant)... does anyone have any advice on this configuration?

Thank you!
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Question by:dkattan
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9 Comments
 
LVL 11

Expert Comment

by:DIPRAJ
ID: 34161798
better you go for HA mode for the ASA.
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Author Comment

by:dkattan
ID: 34161839
What do you mean? I am planning on using the 2 ASAs with Active/Standby mode would that be HA?
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Expert Comment

by:Alan Huseyin Kayahan
ID: 34162656
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LVL 7

Expert Comment

by:kellemann
ID: 34163637
Just so I understand correctly: Are you worried about traffic getting routed directly between vlans on the 3560s, instead of being handled by the firewalls, or is that your intention?
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Author Comment

by:dkattan
ID: 34164095
I am worried about both. Reason being, there are a dozen or so servers behind the 3560s that should not have access to each other, the sames rules on the firewall should apply to the 3650
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Accepted Solution

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kellemann earned 250 total points
ID: 34164384
You don't mention how many VLANs you have, and how complex the interaction between them is, so I'm not sure what the right strategy should be. If you can keep the rules simple, I would go with a blacklist strategy. Assume the following:
Vlan 10 is not allowed to communicate with vlan 20. Create an ACL where you deny traffic from vlan 10 to 20, and permit everything else:

ip access-list extended VLAN10-in
 deny ip 10.1.10.0 0.0.0.255 10.1.20.0 0.0.0.255
 permit ip any any

interface vlan10
 ip access-group VLAN10-in in

You can't have both ways though. Either you filter the vlans at the switch level or you do it at the firewalls. No need for identical rules on the ASAs. Keep the vlan specific stuff at the switches, and filter everything else at the firewalls.
Mind you, this is only if you want the fastest possible inter-vlan communication. If you would like more control, and don't mind taking a hit on speed, simply don't give the vlans ip addresses on the swithes, and handle everything at the firewalls.
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LVL 29

Assisted Solution

by:Alan Huseyin Kayahan
Alan Huseyin Kayahan earned 250 total points
ID: 34165254
Your setup is a common practise. Firewall has nothing to do with intervlan routing or intervlan filtering. It is handled (it should be) in L3 switch. Since active/standby pair replicates configurations between each other, all you have to worry about is to keep your switches with identical ACLs. If you cant afford ciscoworks, my above posted recommendation should work
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Expert Comment

by:Qlemo
ID: 34488504
This question has been classified as abandoned and is being closed as part of the Cleanup Program.  See my comment at the end of the question for more details.
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