Can egress data pass through the same WAE twice

Unanswered Question
Oct 22nd, 2008

I recently tried to install a WAE-512 at one of our sites as an inline deployment.

The site has 2 routers, one is the main data router and is the HSRP active router for the data vlan. The other router is the main voice router and is the HSRP active router for the voice VLAN. The reason we have different routers as the gateway for each VLAN is that we need all voice traffic to go through the voice router as it has SRST capabilities, therefore under normal operating conditions, we expect voice traffic to hit the voice router, and then go over to the data router to get onto the WAN/Call manager.

I planned on optimising both connections using the WAE, thus utilising all ports on the inline adaptor.

What's occured to me is that voice traffic will actually be passing through the WAE twice at this site - once through inline pair 1 to get to the backup router, then through inline pair 0 to get to the main router.

When we installed it this morning, there were connectivity problems between the switch and the voice router.

What I need to know is, what are the effects of the traffic passing through the same WAE twice? Is this not a good idea? Could it potentially have caused the problems we had?

The voice traffic itself is UDP so I wouldn't expect the WAE to do anything with it in any case.

Many Thanks in advance,


I have this problem too.
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Zach Seils Thu, 10/23/2008 - 05:20

Hi Dom,

For optimized connections, the flow you describe could result in the WAE thinking the traffic is looping (and dropping the connection). Since you are specifically talking about VoIP traffic, which should be handled as pass-through, it may work. That being said, I would not recommend it. What you'll need to do is create a transit connection between the routers over which no interception occurs. You can do this one of two ways:

1. Directly connect the routers using a spare physical interface on each router. This crossover should be the preferred path from a routing perspective for traffic going between the routers.

2. If you don't have a free physical interface on the routers, you can trunk the existing LAN connections and create a new VLAN for router-to-router traffic. This VLAN should be the preferred path from a routing perspective for traffic going between the routers. You would then need to exclude this VLAN from interception in WAAS (ex: no inline vlan X').



d-fillmore Thu, 10/23/2008 - 06:26

Many Thanks Zach, Yeah the UDP traffic should be passthrough but it's been pointed out to me that the call setup traffic is TCP.

Cheers, Dom

Zach Seils Fri, 10/24/2008 - 06:19

True, although VoIP control traffic is set to pass-through by default. In any case, we should design for the looping condition I described.




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