asymmetric routing

[simsim]

Hi , 

If there is asymmetric routing how the  firewall process the packet if it is in routed mode . 

How it process the packet if it is in vwire mode  and there is asymmetric routing ? 

Thanks

[reaper]

the firewall makes it's primary forwarding decissions based on zones in the case of vwire, you would likely have 2 sets of vwires to handle each 'channel', if you configure both sets of vwires to the same zones, the sessions would remain intact and flow normally in Layer3 mode it becomes a little more difficult: on a single chassis you may need to set up policy based forwarding with symmetric return enabled (or may not need this, depending on the situation), the zones mentioned above still hold true a solution to asymmetry in layer3 is to set up a cluster in HA-Active/Active mode which was designed specifically to address asymmetric routing

[simsim]

Hi,

I think i don't understand all these stuffs . sorry for that 

can yo u explain the following ? 

1) you said "ou would likely have 2 sets of vwires to handle each 'channel',"

2) on a single chassis you may need to set up policy based forwarding with symmetric return enabled

Thanks 

[reaper]

---

1) you said "ou would likely have 2 sets of vwires to handle each 'channel',"

asymmetric routing has packets egressing via one path and returning via another. It is paramount that you get the firewall placed so that it is able to see both flows of data and can inspect the entire transaction, else the firewall is rendered useless

this could be achieved by placing a vwire in each path, having all zones matched up, to create a virtual 'double whammy' vwire

---

2) on a single chassis you may need to set up policy based forwarding with symmetric return enabled

when your firewall needs to perform routing and is receiving packets for the same conversation on different interfaces, things can get messy real quick. we have a feature called Policy Based Forwarding which allows you to bypass normal routing and force packets out of a different interface, and in this feature there's an option called symmetric return which 'fixes' asymmetry by forcing returning packets out of an interface that is not supposed to be used if you would follow regular routing

---