Lag while hosting Server

[Balexgt]

I seem to have quite an issue with my Private wow server. When i have the server running on a LAN everything works fine for every1 connected, but when i host it using a DNS server so that ppl can connect via the internet it seems that any incomming connections work great but the connections from inside the LAN are so slow that we get disconnected if we even try and move. we tryed to set our realmlist to the DNS name and the actual lan ip and both work but we are still getting disconnected and it takes like 2 min to cast 1 spell or use 1 ability. the server is not running wow itself, just other computers on the network. if u need me to copy and past any info from my server config files plz let me know. i just need to figure this out tyvm.

Server using:
ArcEmu Rev 1974
AMD Athlon 64 3200+
1GB DDR
7200 RPM HDD
10/100 LAN

[Balexgt]

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