A few years back, it was considered best practice to have network devices from different vendors. For example, being a complete Cisco shop was not considered to be the best practice. However, companies, nowadays, are usually opting for a single vendor for all their network and security hardware needs. Is having a multi-vendor network still considered to be more secure?
This is a good question.
You have raised a valid concern from Operators (Service Providers/Enterprise Customers etc.) perspective. They are divided in this matter and some think that having security appliances (firewalls, IDS/IPS etc.) from different vendors make it more challenging for intruders (or attackers) to gain entry into your network. On the other hand, vendors don’t like this idea and they want you to buy every thing (complete solutions) from them and they make life of Operator technical staff easy in terms of configuration/troubleshooting etc. (as you are dealing with one vendor only). For example, vendors like CISCO allows you convenience of importing configurations across their different security devices using solutions.
In my opinion, it is essentially same thing. Either you go with different vendors or same vendor, it won’t make much difference. However, if you decide to go with different vendors then you need more expertise and understanding of both vendor’s product and operation knowledge. At troubleshooting times, you also need skills and experience to figure out the issue which is challenging when you deal with two different vendors (vendor technical staff will involve less in these situations as they only limit themselves to their product support). So I would recommend to go with one vendor only unless that vendor doesn’t offer the exact product you are looking for.