ASA5520 is capable of running up to 750 IPSec VPN tunnels, so if you have no more than 750 IPSec VPN tunnels, you can definitely consolidate them into 1 ASA5520.
However, ASA can't have 2 default gateway configured on 1 box, so you can't have 2 different ISP if you would like to configure 2 default gateways. But if you are using 1 ISP just for the site-to-site VPN tunnel and the other ISP just for normal internet access and remote access VPN, then yes, you can connect 2 different ISPs. One ISP will have the default route configured, and the other ISP will have static routes configured for the remote peer and remote site-to-site VPN LAN.
Table of ContentsIntroductionVersion HistoryPossible Future
UpdatesDocuments PurposeNAT Operation in ASA 8.3+ SectionsRule Types
Network Object NATTwice NAT / Manual NATRule Types used per SectionNAT
Types used with Twice NAT / Manual NAT and Network Obje...
Table of Contents Introduction:This document describes details on how
NAT-T works. Background: ESP encrypts all critical information,
encapsulating the entire inner TCP/UDP datagram within an ESP header.
ESP is an IP protocol in the same sense that TCP an...