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I have a pair of Cisco ASAs running in active/standby failover mode which I manage using the management interface. Lately, I frequently have to travel and the VPN to the university's LAN has different IP subnet from the ASA management interface. So, I cannot access the management interface when using different IP subnet.

My understanding is this is due to asymmetric routing issue and the only way to overcome this is by using multiple context mode.

Right now, I am not clear about the changes of configuration to be made on ASAs. The ASA uses EIGRP.

Note: The pair of ASAs that I am responsible to are not the firewall for entire university campus, just for a single network which contains freenas servers for a few researchers. The VPN gateway is at different firewall and managed by official IT team.

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  • You need to get the network where it ASA management interface is to be announced so that it is reachable from the VPN gateway. You probably have it inside the ASAs, so you will not be able to reach it from outside the ASAs (good practice). It boils down to: do you want to protect the ASA management interface from the outside, or not.
    – Ron Maupin ♦
    Apr 9, 2016 at 15:03
  • @RonMaupin Sorry, I do not understand what you meant. The subnet of management interface is reachable from anywhere because the campus has dedicated subnet for management of all devices. The issue is inbound traffic to the IP of management interface enters through the management interface, but outbound traffic from the IP of management interface goes out from OUTSIDE interface. The ASA has 3 active IP interfaces which are OUTSIDE, INSIDE and management interface.
    – Ron Vince
    Apr 9, 2016 at 15:14
  • Did any answer help you? If so, you should accept the answer so that the question doesn't keep popping up forever, looking for an answer. Alternatively, you can post and accept your own answer.
    – Ron Maupin ♦
    Nov 19, 2022 at 22:50

2 Answers 2

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As far as I can remember, there are two easy things that will make this work. First, you need the command management-access <your-mgmt-nameif>. This is a global config command. Here's the documentation for this: https://www.cisco.com/c/en/us/td/docs/security/asa/asa84/configuration/guide/asa_84_cli_config/access_management.html#30377

Second, you might need some kind of static NAT that allows the inbound connectivity to override the outbound PAT that might be there. So, something in the style of this:

nat (mgmt,outside) source static obj-mgmt-net obj-mgmt-net dest obj-vpn-subnet obj-vpn-subnet

As a side note, I always avoid creating a dedicated management interface on ASA firewalls. I always manage them using the inside interface. So I always do management-access inside.

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You have seemingly described a firewall that is hosted inside another firewall (where the VPN is hosted). If that is the case, simply allow management access on the outside interface of your firewall and you will be able to reach it like any other device on the network inside the firewall where the VPN is connected.

Enable SSH and/or ASDM on the outside interface and allow the IP address block used for VPN clients. That's it.

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