I have a problem with my Cisco 5508 ASA Firewall and it is connected via site to site VPN to my Sonicwall firewall. Every time the internet on the other (Sonicwall) peer goes down or switched from Primary to Secondary and vice versa only (not all) certain VLANs can communicate to and from the Cisco Firewall.
my Site A (Cisco): 1 VLAN only -192.168.0.0/24
my Site B (Sonicwall): 6 VLANS - 172.20.1.0/24,172.20.3.0/24, 172.20.5.0/24, 172.20.7.0/24, 172.20.9.0/24 and 172.20.30.0/24
when the internet switched from primary to secondary on the sonicwall side sometimes only 1-3 VLANs can communicate to and from the Cisco (only these vlans went through 172.20.1.0/24,172.20.3.0/24, 172.20.5.0/24) and all the reset were dropped. what i always do is to logout the session and initiate it again so that all vlans can be contacted again.
what should be the possible reason for this?
I hope someone can help me with this one. I am using ASDM by the way i seldom use CLI.
There could be many. You need to describe the VPN. Are you using dynamic ipsec of static? Do you have dynamic routing in place which can be causing this? Do you have multiple links to exist VPN? Check if you are having incorrect nat statements which are forcing the traffic is certain directions.