7.0->7.1->7.2->8.2->8.4(6)->9.1x
http://public.myswsrv.de/Cisco/Firewall/ASA/System/8.x/8.2.x/
https://software.cisco.com/download/release.html?mdfid=279513399&softwareid=280775064&release=7.6.1
https://supportforums.cisco.com/t5/security-documents/asa-8-3-upgrade-what-you-need-to-know/ta-p/3127078
5520跑8.3以上版本内存要2G，其他型号内存需要都不一样
7.4(java7+) https://192.168.70.29:55555/admin/public/asdm.jnlp
ASA5520(config)# boot system disk0:/asa821-k8.bin
ASA5520(config)# no boot system disk0:/asa724-k8.bin
ASA5520(config)# write
ASA5520(config)# reload noconfirm
You should not have problem from 7.2 to 8.x, as the Cisco documentation says: "Therefore, to upgrade from Version 7.0 to Version 8.2, first upgrade from 7.0 to 7.1, then from 7.1 to 7.2, and finally from Version 7.2 to Version 8.2 (8.1 was only available on the ASA 5580)." When booting the first time, configuration adjustement will be done if needed.
So if you‘re already in 7.2 it‘s ok. Just take care that when both device run different OS version at the same time you will lost the failover link. (So you can‘t upgrade without interrupt)
2.基本操作
教程
https://www.cisco.com/c/zh_cn/support/security/asa-5500-series-next-generation-firewalls/tsd-products-support-series-home.html
https://www.cisco.com/c/en/us/about/security-center/firewall-best-practices.html
PIX vs ASA
http://blog.51cto.com/fengyeweilan/169046
CDP 协议
防火墙一般为了安全考虑，不支持 CDP 或者 LLCP 协议
原文：https://www.cnblogs.com/ilinunix/p/11234830.html