Hello - Just would like to state that I really do like Mikrotik and use it nearly everywhere on my networks. Here is a link that I found on Slashdot.org today.
Have a read - maybe someone will understand it better than I.
http://www.renesys.com/blog/2009/02/longer-is-not-better.shtml
As for the blame, network operators (SuproNet) should obviously read their router documentation and test any proposed changes in a lab environment to see if they get the results they expect. Router vendors should check bounds on input parameters (MikroTik) and on boundary conditions (Cisco). ISPs should filter out obvious useless garbage, like ridiculously long AS paths and unrouteable (private) IP addresses.
in one word: RTFM 
(but i agree that there should be a check on input parameter in the AS Prepend option to avoid those dumb network admins 
)
I agree - but I thought I would post what I found so the fine folks at Mikrotik could take a look - maybe there is a bug that should be repaired, maybe not. Just thought I’d be a good Mikrotik user and report back to the ‘mothership’ that is Mikrotik!
If it matters, I’ve been running BGP for nearly two years connected to the public internet with mainly Cisco peers - the sessions seem rather stable. I have had a few problems lately however. Unfortunately, looks like I may have to buy Cisco product as no one can offer assistance in the peering community as they all have Cisco, I’m the ‘odd-ball’.
from Winbox, we are allowed to set prepend up to 2^32… and 255 seems to be the default value
Be aware this really isnt a ROUTEROS issue other than its possible to send info thats not sane.
The bug is in the older cisco IOS’s running on some routers. If they update their IOS, (may require
memory upgrade on some models, EXPENSIVE!), the issue is non existant. This ONLY affected
cisco routers running older IOS verions. Anyone with one of those running BGP shouldnt be doing
it anyway.
Ray
When you are editing prepend from console, you are allowed to set it 1…16
When you are editing prepend from winbox, you are allowed to set it 1…2^32
1st mistake, we are allowed to set it up to 2^32
2nd mistake, 255 seems to be the default value, should be 0 or null (=> not set => not used)
3rd mistake, routing daemon accepts these values even they are strange
In addition, we have the old 'n faulty Cisco routers.
I notice also from the article that the http://www.mikrotik.cz/ link seems to go to a localised mikrotik site then redirect to a spam site?
Ouch, what a crap! I just defended Mikrotik on the Nanog mailing list a few days ago when this was a hot topic, stating that this must have been fixed in recent ROS versions as the CLI didn’t allow me to enter anything else than 1-16.
I presume this will be fixed ASAP in winbox as well.
Feature Request!!! : Forum tab to talk about BGP. I’ve to commit a search every time i’ve a trouble with BGP and not always i find the solution that might be already talked about.
I second this request.
We are using RB1000’s as BGP borders, and as of now, I don’t dare do anything except just announcing my own prefix to two upstream peers. I think more BGP focus would be a good, and for this forum to share their common BGP experience would only be beneficial to the continued internet stability
MikroTik: Routing the World, Crashing the World Internet - anything you need for small fees!
Guys, I like ROS power! 
rolf