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ISADSL and MiktoTIK Router

So we have an ISADSL Business Uncapped Shaped service from IS. I've been shouting at them for weeks now, because I just do not get anything out of this service. They looked at it, Telkom looked at it and still nothing.

Now, I did ask them if I could use my own modem, but no, I have to use the modem from them.

So today, I loose my diginet line and have to push the whole company onto my IS ADSL service.

Having users shouting at me, I decided to really look at this problem and after many hours I found that for some reason the router from IS has issues with mishapped MSS and MTU's on the Ethernet. Now this is something I assumed any good router would resolve, but not the one from IS.

So I added "change MSS" mangle rules to the Ethernet on the Mikrotik connected to this router:
/ip firewall mangle
add action=change-mss chain=forward comment="" disabled=no in-interface=ether2 new-mss=clamp-to-pmtu protocol=tcp tcp-flags=syn tcp-mss=1441-65535
add action=change-mss chain=forward comment="" disabled=no new-mss=clamp-to-pmtu out-interface=ether2 protocol=tcp tcp-flags=syn tcp-mss=1441-65535

Now it is strange how well this service performace!

Add some simple Queues:

/queue type add kind=pcq name=PCQ-ISADSL pcq-classifier=src-address,dst-address,src-port,dst-port pcq-limit=50 pcq-rate=0 pcq-total-limit=2000

/queue simple add burst-limit=0/0 burst-threshold=0/0 burst-time=0s/0s comment="" direction=both disabled=no dst-address= interface=ether2 limit-at=4M/512k max-limit=4M/512k name=ISADSL parent=none priority=1 queue=PCQ-ISADSL/PCQ-ISADSL total-queue=PCQ-ISADSL

/queue interface set ether2 queue=PCQ-ISADSL

And watch this service fly!!!!

Hope this helps somebody.


  1. Was this a billion router ? I had the same problem with a billion router and once they changed the router to a cisco the problem was resolved.



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