Running a mixed UnrealIRCd 3.2 and UnrealIRCd 4 network

You can link UnrealIRCd 4 servers to a 3.2.x network. You can do so if are in the process of upgrading your 3.2.x servers. There are however a few things that won't work properly.

'NOTE: This article was written in 2015 when 3.2.x was still supported and 4.x was new. However, since January 1, 2017 UnrealIRCd 3.2.x is deprecated and should no longer be used at all!'

As a shorthand, follow these simple rules:
 * 1) If your 3.2.x IRCd has SSL enabled then you must use version 3.2.10.3 or later
 * 2) If you have more than one UnrealIRCd server then be sure to link in UnrealIRCd 4 as a leaf. Your hub should be upgraded last.
 * 3) On UnrealIRCd 4 use /SPAMFILTER add -posix when adding spamfilters
 * 4) Change any admin-only channels from +A to +O

For more information, see below.

= Why you may want to run a mixed network = Ideally you should run your network 100% with UnrealIRCd 4 servers. However, we don't live in an ideal world. Many people run an UnrealIRCd 3.2.x network and there are two reasons why you may be running a mixed UnrealIRCd 3.2.x - UnrealIRCd 4 network: In both cases you will run a mixed network for a limited amount of time (say, a couple of weeks).
 * 1) You may wish to evaluate UnrealIRCd 4. You can do so on a separate test network but some may opt to link in an UnrealIRCd 4 test server to the existing 3.2.x live network.
 * 2) When you're ready to migrate your UnrealIRCd 3.2.x network to UnrealIRCd 4 you can choose to upgrade all servers at once, or you may go the slow route and upgrade servers once at a time.

= Important recommendations = We don't recommend running a mixed network for many months because as long as you run a mixed UnrealIRCd 3.2.x - UnrealIRCd 4 network you'll encounter a number of issues. These can only be resolved by running a true 100% UnrealIRCd 4 network.

Also, as long as you run a mixed network, you should probably keep your hub at 3.2.x. Upgrade the hub only after all the other 3.2.x servers have been upgraded to UnrealIRCd 4.

We use the following colors to indicate the impact of issues that occur when running a mixed network:

= Linking toplogy = As long as you run a mixed network your UnrealIRCd 4 server should link in as a leaf, and your hub should be upgraded to UnrealIRCd 4 at the end (last server to upgrade)

= Linking issues =

The fix is simple: use 3.2.10.3 or higher on the 3.2.x side.

= Issues with opers & user modes = In UnrealIRCd 4 we no longer have "Network administrator" and other such oper levels. These have been replaced with "oper classes". See Changes in the Oper block. You can still use titles in /WHOIS like "Network administrator", but ircops no longer have special ircop level user modes associated with them: user modes O/a/A/N/C have been removed.

We also removed or renamed some other ircop-only user modes, such as 'v' (DCC rejection notices) to snomask 'D'.

= Issues with channel modes =

= Issues with extended bans =

= Issues with spamfilters = In UnrealIRCd 4 we switched the default regex engine from 'POSIX' to 'PCRE2'. We also changed the syntax of the /SPAMFILTER command so you can specify which engine to use (/SPAMFILTER add -type..). See Upgrading from 3.2.x: Spamfilter

= Other = There are many features UnrealIRCd 4 introduces, including increased SSL security, better linking, safer killing of (the right) users, etc. These will only be effective on a 100% UnrealIRCd 4 network.