ACE 4700 one-arm design with SSL termination

Question

Hi,
We are evaluating the one-arm design for the ACE 4700 and need some clarifications:
1. Are there any limitations in the one-arm design and the SSL offloading
2. Can the ACE be configured with an IN and an OUT vlan to the router
CLIENT -> Router -> ACE IN -> ACE OUT -> Router -> Server Vlan
so that the SSL and the clear text traffic is in a separate Vlan?
3. In some sample configuration i saw SNAT configuration on the ACE to modify the client IP. This i assume is for instructing the return traffic from the server to go through ACE? Using SNAT we eliminate the requirement for NAT or PBR on the router? Will i still be able to insert the client IP address after the SSL offload?
I would appreciate if you can share some sample configs
Regards,
George Georgiou

Answer 1

There are two ways to implement One Arm topology.
1. One Arm with PBR & 2.One Arm with SRC NAT
PBR/Source Nat is needed to ensure that the return traffic from Real Servers should not bypass ACE.
1. Are there any limitations in the one-arm design and the SSL offloading
The limitations/config issues I can think of are following
One ARM with PBR:
Direct access to Servers require the enabling of Assymtric routing (by turning off Normalization). If direct server access is not required then you dont need to enable assymtric routing. Now for these assymetric connection (Direct Server Access return traffic) its required to purge idle connections more frequently (default being one hour).
One ARM with SRC NAT:
You will loose the client information. Server logs will show the connections initiated from NAT IP Pool configured on ACE.
2. Can the ACE be configured with an IN and an OUT vlan to the router
CLIENT -> Router -> ACE IN -> ACE OUT -> Router -> Server Vlan
so that the SSL and the clear text traffic is in a separate Vlan?
Yes you can do that but wouldnt it make it routed mode topology?
3. In some sample configuration i saw SNAT configuration on the ACE to modify the client IP. This i assume is for instructing the return traffic from the server to go through ACE? Using SNAT we eliminate the requirement for NAT or PBR on the router? Will i still be able to insert the client IP address after the SSL offload?
As I said earlier you loose the Source IP address with SRC NAT. But with ACE you have an option to use header-insert and insert this source ip as an HTTP Header.
Details at
http://www.cisco.com/en/US/docs/interfaces_modules/services_modules/ace/v3.00_A1/configuration/slb/guide/classlb.html#wp1040008
HTH
Syed Iftekhar Ahmed