To reproduce:
(Turn networking on?)
Goto Admin->Networking->Peers
Under "Add a new host", enter clsa_mnet_a.mroomsonline.com
Moodle (not Mahara)
Press the "Add host" button

Error message: "Invalid URL parameter."

I believe this is being rejected by clean_param in this code (line 82 in admin/mnet/peers.php):
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$temp_wwwroot = clean_param($form->wwwroot, PARAM_URL);
if ($temp_wwwroot !== $form->wwwroot)

{ trigger_error("We now parse the wwwroot with PARAM_URL. Your URL will need to have a valid TLD, etc."); print_error("invalidurl", 'mnet','peers.php'); exit; }

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(I can connect to the host correctly if I use clsamneta.mroomsonline.com)