[cisco-voip] Expressway E Firewall Rule Activation

[Pawlowski, Adam]

Ryan,

The “tl;dr” is that we were sort of given the recommendation by Cisco to just run it with the single interface given our environment and requirements, and hasn’t given us any trouble that I can recall.

Long story is …

Our environment ends up being the driver for a lot of this, as it is sort of a historic design from the early internet, with just about everything on public address space, and various services and networks secured behind firewalls as needed from internal and external alike.

In the dual interface design, the outside interface sits in a “DMZ” with a firewall, which we don’t have available explicitly. There is a border firewall but that isn’t really its function. The inside leg has to sit somewhere as well, which is a place that doesn’t exist.

We did have a competitor’s border proxy become compromised in the past due to a software update, and this model where the inside wasn’t properly secured – and given our current VMWare topology, creating another zone to hairpin traffic around to separate that inside interface wasn’t in the cards. Not to mention the annoyance of trying to setup split routes on this device to allow some traffic to go in, some to go out, in an environment that is MRA only.

If you trust the E enough never to be a bad actor, then you could put that interface in the same zone as your other collaboration appliances, like the Expressway C, but, we didn’t want to do that either really.

Given that, we did have a call with Cisco to discuss this, and with representation from the Expressway group they recommended that we stick with the single interface design.  That was based on the public addressing (so we could avoid NAT reflection) and that despite the pipe dream of everyone wanting HD video calling and mobile client access, we didn’t see that we’d be pushing that much traffic.

As it is, the E clusters sit in a collaboration DMZ, where they are independent from any of our other appliances and treated like any other host on our network. Our application firewalls do not allow anything in from the Expressway E since the C tunnels to it, so really the only thing lacking from a security standpoint there could be containment of that host, but, we chose to guard from it instead.

Since we installed it back on X8.8 or whatever, I’d noted that rebooting the appliance does not reapply the internal rules, which can easily be forgotten, and would need to be remembered if you run a VMWare HA policy that restarts the guest.

That all being said the worst that we have seen are various SSH attempts (on any port, the zone tunnel, administrative SSH, doesn’t matter) until the rules are put back up. We could tighten them on the border once that becomes available to do so.

The B2BUA is invoked on calls within the appliances sometimes which can cause some confusion with attempting to read logging if need be, but it hasn’t otherwise caused us any trouble.

Adam



From: Ryan Huff <ryanhuff at outlook.com>
Sent: Tuesday, April 30, 2019 10:13 AM
To: Pawlowski, Adam <ajp26 at buffalo.edu>
Cc: cisco-voip at puck.nether.net
Subject: Re: [cisco-voip] Expressway E Firewall Rule Activation

That seems odd and not been my experience. Let me ask; why are you using the application firewall rather than the actual firewall (another reason all our edge’s should be using dual interfaces with LAN1 and LAN2 in their own separate security zones)? Is there a reason you have to, in other words?
Thanks,

Ryan

On Apr 30, 2019, at 08:49, Pawlowski, Adam <ajp26 at buffalo.edu<mailto:ajp26 at buffalo.edu>> wrote:
Figured I’d also ask this question

I note that it seems like any time I reboot an Expressway E, I have to go and re-activate all the firewall rules. They don’t seem to activate automatically.

Is there something I missed or is this really what’s necessary?

Adam


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