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Failover between 2 SDSL lines

Posted on 2006-10-22
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Last Modified: 2012-05-05
Hi -

I have the following configuration on a new site:
2 RTRs Cisco 1841 with SDSL interface + 2 ASA 5510 firewalls + two 3750 switches (stacked). We want a solution completely redundant (not interested in load-balancing) and I was interested by the following case:

http://www.experts-exchange.com/Hardware/Routers/Q_21592805.html

however in this scenario the main concern is the firewall which is not redundant.

few questions:

- Will OSPF work with SDSL lines?
- If I configure the ASAs in a Failover configuration and connect the 2nd SDSL ISP to another ASA's Interface, which automate routing options will I have?

Thanks for any tips

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Question by:Matsco
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by:lrmoore
ID: 17784960
Yes, OSPF will work regardless of the WAN link. You're only talking OSPF between the 1841's, the ASA's and the 3750 stack.
You need a switch between the two 1841 routers and the 2 ASA's in order to have full redundency. Actually, you'd need two for total redundancy. Something like 2x2950/2960
ASA's in Active/Active or Active/Standby failover mode
1841's broadcast default to ASA
ASA broadcasts default to 3750

DSL1                       DSL2
1841-1                    1841-2
FA0/0  FA0/1 --X-- FA0/1  FA0/0
  |                                    |
SW1 ---x-over-x2---------SW2
    |      (OSPF area0)      |
    |                               |
ASA1 Eth0                    ASA2 Eth0
ASA1 Eth1                    ASA2 Eth1
           |  (OSPF area1)  |
           |                        |
           3750 switch stack
           3750 switch stack


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by:Matsco
ID: 17787228
Thanks lrmoore,

sorry but I don't understand your scenario above, would I require 4 ASAs in total?  If I use my two ASAs  in Active/Standby configuration, I don't understand how to work out this without connecting the 2nd DSL router/VLAN to an additional IF of the Active ASA.
ASA2 as "stand-by" firewall would not  be considered in this implementation, would it?

thanks in advance
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Expert Comment

by:lrmoore
ID: 17787796
2xASA - I was just trying to illustrate the interfaces being in different OSPF areas.

By putting a switch between the 2x 1841 routers and the 2x ASA's, both ASA's "outside" interfaces connect to both DSL lines. This is preferred over one ASA connecting to one line and the other to the 2nd line.
By using 2 cross-connected switches, and also cross-connecting the two routers you have 100% hardware redundancy.
It works best with ASA2 in standby mode, but works equally well in Active/Active mode.
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by:Matsco
ID: 17791650
Lrmoore

I apologise, probably I didn't give  full details; My routers are both configured "no NAT", each one with  a different Public Net Id on the Eth0 interface.

1842-1 using Net id 87.224.22.88/255.255.255.248 on Eth0 side
1841-2 using Net id 88.96.149.96/255.255.255.248 on Eth0 side

The ASA firewall does static and dynamyc NAT. At the moment on the outside IF of the firewall I have a Public IP of my primary connection using 1841-1

DSL1                                                     DSL2
1841-1 (Eth0 87.224.22.89/29) -----X---- 1841-2 (Eth0 88.96.149.97/29)
 ¦                                                            ¦
SW1  -------------------X--------------------SW2
¦                                                             ¦
ASA1 (Out 87.224.22.94/29)                   ASA2 (stand-by)

As ASA1 will be the primary active firewall with outside IF set to 87.224.22.94, in this scenario it will never "talk" with 1841-2, Am I wrong?
How would you work this out?


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lrmoore earned 250 total points
ID: 17791842
This does, indeed change things. My solution above would only work if you have your own subnet, or double-nat through the second DSL line. Inbound failover is a challenge..

I would still do Active/Standby and use a 3rd interface of the ASA to connect to DSL2 in a vlan
No reason to X-over between the 2 routers

Switch1 + switch2 have vlans DSL1 and DSL2
1841-1 Eth0/0 = DSL1
ASA1 outside = DSL1
ASA2 outside = DSL1

1841-2 Eth0/0 = DSL2
ASA1 BackupIf = DSL2
ASA2 BackupIf = DSL2

Since the ASA pair appears as just one appliance, you can use this configuration to support failover routing to the second DSL line. In this case, you don't even need OSPF unless you want to run it between your 3750 stack and the ASA pair.
http://www.cisco.com/en/US/products/hw/vpndevc/ps2030/products_configuration_example09186a00806e880b.shtml

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Author Comment

by:Matsco
ID: 17792429
that's what I was looking for,  Cisco should really reward you Man!

I have to Upgrade IOS to 7.2(1) and will test it in the next couple of days

thanks a lot

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Expert Comment

by:lrmoore
ID: 17792483
You'll really like the newest ASDM GUI with 7.21
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