[RESOLVED] srcds intermittent issues, gametracker & steam server list

[issac]

First, sorry if this is in the wrong forum. Forgive me for my lack of perception, but the readme wasn't clear enough to help me decide where this issue would go. (tl;dr: I'm dumb. )

I'm having some troubles keeping my server "online." Online is in quotes because the issue feels bizarre to me.

On gametracker.com, my server intermittently toggles between "Alive" and "Dead."
The server does not show up in the steam game browser, either.

Players are able to connect manually.
ex, in console
connect withfrosted.com:27016, or
connect 173.166.81.181:27016

When the map changes, gametracker sees it again every time. But then it intermittently toggles again and the server never shows up in the game browser.

I have researched as much as I could, but I couldn't find anything at all.
Keep in mind there are absolutely no software firewalls.

Any help would be greatly appreciated.

Quick notes:
In startup line, when no -ip is specified:
No one is able to connect.
-ip 192.168.10.103
No one is able to connect.
-ip 0.0.0.0
People are able to connect.

BASIC INFO
Server OS: Windows XP Professional SP3
Processor: Virtual CPU, 2 cores (VirtualBox)
Ram: 2GB
Game(s): Counter-Strike: Source
Start Up Command: srcds.exe -console -autoupdate -game cstrike -secure -port 27016 -ip 0.0.0.0 +map gg_simpsons_street +maxplayers 18
Admin Mods: Mani Admin, Metamod (no plugins currently), HLStatsX:CE

INSTALLING INFO
Full Install Command:
HldsUpdateTool.exe -command update -game "Counter-Strike Source" -dir C:\hlserv\cstrike\WFServer2

NETWORK AND BANDWIDTH INFO
(This is only needed if you are having a slot-count, bandwidth, or connection issue.)
Bandwidth: 22mbps/5mbps
Router: TrendNet TEW-639GR
Local IP of Server: 192.168.10.103
Port Forwarding Screen Shot: All ports are forwarded correctly. I'd be happy to grab a screenshot if absolutely necessary.

[issac]

Resolved, it seems. I'm not going to mark it yet because I want to monitor it for a couple days to make sure it doesn't drop.

I didn't have -all- of the necessary UDP ports open, I would guess. A minor adjustment to the open UDP ports after changing the following below.
Also, +ip 192.168.10.103 (local IP) seems to work with a +ip switch.

Once I confirm it doesn't go down, I'll update the thread.

Edit:
Issue is resolved.
Modified startup line:
srcds.exe -console -autoupdate -game cstrike -secure -port 27016 +ip <local IP> +map gg_simpsons_street +maxplayers 18
Open TCP/UDP Ports: 27000-27050
Open UDP: 1200
Open TCP/UDP 27500 for hlstatsx