Bug #12798
closed
Web UI allows IP Aliases and 1:1 NAT to share IP on same interface - ends in routing issues
Added by Paul Parkin over 3 years ago.
Updated over 3 years ago.
Category:
Aliases / Tables
Affected Architecture:
All
Description
I've found an issue where if you configure an IP Alias and use that same external IP for a static (1:1) NAT then issues with routing occur where all gateways become unavailable. A genericised example below based upon my config:
Interface: WAN
WAN IP: 1.2.3.4/32
WAN GW: 5.6.7.8 (non-local gateway)
Alias: 1.2.3.5/32
And a 1:1 NAT for 1.2.3.5/32 to host 10.1.2.3/32.
The symptoms are a loss of connectivity via a gateway after a while (it's not instant) whether gateway monitoring is enabled or not. Connectivity is instantly restored by deleting the IP aliases.
This is also an issue in 2.5.2, but I hadn't figured out what caused the issue until today having upgraded to 2.6/22.01.
- Status changed from New to Not a Bug
I have a few systems here with that kind of configuration and none have the problems you describe, and that is a very common use case of VIPs and 1:1 NAT. You might be hitting some variation of #11545 but there isn't enough information here to tell, and it's not something we can reproduce.
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This isn't a request for support... I've already specified what the symptoms are, the cause and how to fix it. :)
I am able to replicate this and send somebody at Netgate the XML config from the firewall that will break the installation 100% of the time when applied though restore.
It's possible it's specifically related to your use of a non-local gateway (which is not a typical use case) and not a general NAT+IP Alias issue. If that is the case, the title and description are wrong.
There is NOT enough information here -- please start a forum thread and supply, at a minimum, the contents of the routing table (netstat -rn) and the interface configuration (ifconfig -a) both when it's working and when it is not working. There is a lot more to discuss and diagnose here, the problem report is far from complete and this is not the place to figure out the details.
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